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FINGER PRINTS




  FINGER PRINTS


  [Illustration: FINGER PRINTS OF THE AUTHOR]


  BY
  FRANCIS GALTON, F.R.S., ETC.


  London
  MACMILLAN AND CO.
  AND NEW YORK
  1892

  _All rights reserved_




CONTENTS


  CHAPTER I

                                                                    PAGE

  INTRODUCTION                                                         1

    Distinction between creases and ridges                             1

    Origin of the inquiry                                              2

    Summaries of the subsequent chapters                            3-21

      Viz. of   ii.,  3;   iii.,  4;     iv.,  5;
                 v.,  5;    vi.,  8;    vii., 10;
              viii., 12;    ix., 13;      x., 14;
                xi., 16;   xii., 17;   xiii., 19;


  CHAPTER II

  PREVIOUS USE OF FINGER PRINTS                                       22

    Superstition of personal contact                                  22

    Rude hand-prints                                                  23

    Seals to documents                                                23

    Chinese finger marks                                              24

    The _tipsahi_ of Bengal                                           24

    Nail-marks on Assyrian bricks                                     25

    Nail-mark on Chinese coins                                        25

    Ridges and cheiromancy--China, Japan, and by negroes              26

    Modern usage--Bewick, Fauld, Tabor, and G. Thompson               26

    Their official use by Sir W. J. Herschel                          27


  CHAPTER III

  METHODS OF PRINTING                                                 30

    Impression on polished glass or razor                             30

    The two contrasted methods of printing                            31

    General remarks on printing from reliefs--ink; low relief
    of ridges; layer of ink; drying due to oxidisation             32-34

    Apparatus at my own laboratory--slab; roller; benzole
    (or equivalent); funnel; ink; cards                            35-38

    Method of its manipulation                                     38-40

    Pocket apparatus                                                  40

    Rollers and their manufacture                                     40

    Other parts of the apparatus                                      41

    Folders--long serviceable if air be excluded                      42

    Lithography                                                       43

    Water colours and dyes                                            44

    Sir W. Herschel's official instructions                           45

    Printing as from engraved plates--Prof. Ray Lankester;
    Dr. L. Robinson                                                   45

    Methods of Dr. Forgeot                                            46

    Smoke prints--mica; adhesive paper, by licking with tongue     47-48

    Plumbago; whitening                                               49

    Casts--sealing-wax; dentist's wax; gutta-percha; undried
    varnish; collodion                                             49-51

    Photographs                                                       51

    Prints on glass and mica for lantern                              51

    Enlargements--photographic, by camera lucida, pantagraph       52-53


  CHAPTER IV

  THE RIDGES AND THEIR USES                                           54

    General character of the ridges                                   54

    Systems on the palm--principal ones; small interpolated
    systems                                                        54-55

    Cheiromantic creases--their directions; do not strictly
    correspond with those of ridges                                56-57

    Ridges on the soles of the feet                                   57

    Pores                                                             57

    Development:--embryology; subsequent growth; disintegration
    by age, by injuries                                            58-59

    Evolution                                                         60

    Apparent use as regards pressure--theoretic; experiment
    with compass points                                            60-61

    Apparent use as regards rubbing--thrill thereby occasioned     62-63


  CHAPTER V

  PATTERNS: THEIR OUTLINES AND CORES                                  64

    My earlier failures in classifying prints; their causes        64-66

    The triangular plots                                              67

    Outlines of patterns--eight sets of ten digits given as
    examples                                                       69-70

    Supplies of ridges to pattern                                     71

    Letters that read alike when reversed                             71

    Magnifying glasses, spectacles, etc.                              72

    Rolled impressions, their importance                              73

    Standard patterns, cores, and their nomenclature               74-77

    Direction of twist, nomenclature                                  78

    Arches, loops, whorls                                             78

    Transitional cases                                                79

    The nine genera                                                   80

    Measurements--by ridge-intervals; by aid of bearings like
    compass                                                        82-84

    Purkenje--his _Commentatio_ and a translation of it in part    84-88


  CHAPTER VI

  PERSISTENCE                                                         89

    Evidence available                                                89

    About thirty-five points of reference in each print               90

    Photo-enlargement; orientation; tracing axes of ridges         90-91

    Ambiguities in minutiæ                                            91

    V. H. Hd. as child and boy, a solitary change in one of
    the minutiæ                                                       92

    Eight couplets from other persons                                 93

    One from Sir W. G.                                                95

    Summary of 389 comparisons                                        96

    Ball of a thumb                                                   96

    Results as to persistence                                         97


  CHAPTER VII

  EVIDENTIAL VALUE                                                   100

    Method of rough comparison                                       100

    Chance against guessing a pattern                                101

    Number of independent elements in a print--squares
    respectively of one, six, and five ridge-intervals in
    side                                                         101-103

    Interpolation, three methods of                              103-105

    Local accidents inside square                                    107

    Uncertainties outside it                                         109

    Compound results                                                 110

    Effect of failure in one, two, or more prints                    111

    Final conclusions--Jezebel                                   112-113


  CHAPTER VIII

  PECULIARITIES OF THE DIGITS                                        114

    Frequency per cent of arches, loops, and whorls
    generally, and on the several digits                         114-115

    Characteristic groups of digits                              116-118

    Relationships between the digits                                 119

    Centesimal scale of relationship                             124-126

    Digits of same and of different names                            130


  CHAPTER IX

  METHODS OF INDEXING                                                131

    Use of an index                                                  131

    Method of few conspicuous differences in many fingers            131

    Specimen index                                                   133

    Order in which the digits are noted                              134

    Examples of indexing                                             135

    Effect of regarding slopes                                       135

    Number of index-heads required for 100 sets in each of
    twelve different methods                                     136-138

    _i_ and _o_ in forefingers only                                  138

    List of commonest index-headings                                 140

    Number of headings to 100 sets, according to the digits
    that are noted                                                   142

    Transitional cases; sub-classifications                      143-144

    Symbols for patterns                                             144

    Storing cards                                                    145

    Number of entries under each head when only the first
    three fingers are noted                                          146


  CHAPTER X

  PERSONAL IDENTIFICATION                                            147

    Printers and photographers                                       147

    Use of means of identification to honest persons; in
    regard to criminals                                          148-149

    Major Ferris, Mr. Tabor, N. Borneo                           149-153

    Best digits for registration purposes                            153

    Registration of criminals--M. Bertillon                          154

    Details of _Bertillonage_; success attributed to it; a
    theoretic error                                              155-158

    Verification on a small scale                                158-162

    Experiences in the United States                                 163

    Body marks; teeth                                            165-166

    Value of finger prints for search in a register                  166

    Identification by comparison                                     167

    Remarks by M. Herbette                                           168


  CHAPTER XI

  HEREDITY                                                           170

    Different opinions                                               170

    Larger meaning of heredity                                       170

    Connection between filial and fraternal relationships            171

    Fraternity, a faulty word but the best available                 171

    A and B brothers                                                 172

    Test case of calculated randoms                                  173

    Fraternities by double A. L. W. events                           175

    The C. standard patterns                                         177

    Limitation of couplets in large fraternities                     178

    Test of accurate classification                                  179

    Fraternities by double C. events                                 181

    Centesimal scale applied                                         184

    Twins                                                            185

    Children of like-patterned parents                               187

    Simple filial relationship                                       190

    Influences of father and mother                                  190


  CHAPTER XII

  RACES AND CLASSES                                                  192

    Data for races                                                   192

    Racial differences are statistical only                          193

    Calculations by Mr. F. H. Collins                                193

    Hebrew peculiarities                                             194

    Negro peculiarities, questionable                                196

    Data for different classes in temperament, faculty, etc.,
    and results                                                      197

    M. Féré                                                          197


  CHAPTER XIII

  GENERA                                                             198

    Type, meaning of                                                 198

    Law of frequency of error                                        198

    Discussion of three elements in the loops on either thumb    200-207

    Proportions of typical loops                                     209

    The patterns are transmitted under conditions of panmixia,
    yet do not blend                                                 209

    Their genera are not due to selection; inference                 210

    Sports; variations                                               211




DESCRIPTION OF THE TABLES


                                                                    PAGE

  Summary of evidence in favour of finger marks being persistent      96

  Interpolation of ridges                                            104

  I. Percentage frequency of Arches, Loops, and Whorls on the
  different digits, as observed in the 5000 digits of 500
  different persons                                                  115

  II. Distribution of the A. L. W. patterns on the corresponding
  digits of the two hands                                            116

  III. Percentage frequency of Arches on the digits of the two
  hands                                                              117

  IV. Percentage frequency of Loops on the digits of the two hands   118

  V. Percentage frequency of Whorls on the digits of the two hands   118

  VI_a_. Percentage of cases in which the same class of pattern
  occurs in the same digits of the two hands                         120

  VI_b_. Percentage of cases in which the same class of pattern
  occurs in various couplets of different digits                     120

  VII. Couplets of fingers of different names in the same and in
  the opposite hands                                                 121

  VIII. Measures of relationship between the digits on a
  centesimal scale                                                   129

  IX. Index to 100 sets of finger prints                             133

  X. Number of different index-heads in 100 sets, according to
  the number of digits noted                                         136

  XI. Number of entries under the same heads in 100 sets             139

  XII. Index-headings under which more than 1 per cent of the
  sets were registered in 500 sets                                   140

  XIII. Percentage of entries falling under a single head in 100,
  300, and 500 sets                                                  141

  XIV. Number of different index-headings in 100 sets, according
  to the number of fingers in each set, and to the method of
  indexing                                                           142

  XV. Number of entries in 500 sets, each of the fore, middle,
  and ring-fingers only                                              146

  XVI. Number of cases of various anthropometric data that
  severally fell in the three classes of large, medium, and
  small, when certain limiting values were adopted                   159

  XVII. Distribution of 500 sets of measures, each set consisting
  of five elements, into classes                                     160

  XVIII. Number of the above sets that fell under the same
  headings                                                           161

  XIX. Further analysis of the two headings that contained the
  most numerous entries                                              162

  XX. Observed random couplets                                       174

  XXI. Calculated random couplets                                    174

  XXII. Observed fraternal couplets                                  175

  XXIII. Fraternal couplets--random, observed, and utmost
  feasible                                                           176

  XXIV. Three fingers of right hand in 150 fraternal couplets        181

  XXV. Three fingers of right hand in 150 fraternal couplets--
  random and observed                                                182

  XXVI. Three fingers of right hand in 150 fraternal couplets--
  resemblance measured on centesimal scale                           182

  XXVII. Twins                                                       186

  XXVIII. Children of like-patterned parents                         188

  XXIX. Paternal and maternal influence                              190

  XXX. Different races, percentage frequency of arches in
  fore-finger                                                        194

  XXXI. Distribution of number of ridges in AH, and of other
  measures in loops                                                  203

  XXXII. Ordinates to their schemes of distribution                  204

  XXXIII. Comparison of the above with calculated values             205

  XXXIV. Proportions of a typical loop on the right and left
  thumbs respectively                                                209




DESCRIPTION OF THE PLATES


                                                                    PAGE

  I.--Fig. 1. Chinese coin with the symbol of the nail-mark of
  the Empress Wen-teh                                                 25

  Fig. 2. Order on a camp sutler by Mr. Gilbert Thompson, who
  used his finger print for the same purpose as the scroll-work
  in cheques, viz. to ensure the detection of erasures                27

  II.--Fig. 3. Form of card used at my anthropometric laboratory
  for finger prints. It shows the places where they are severally
  impressed, whether dabbed or rolled (p. 40), and the hole by
  which they are secured in their box                                145

  Fig. 4. Small printing roller, used in the pocket apparatus,
  actual size. It may be covered either with india-rubber tubing
  or with roller composition                                          40

  III.--Fig. 5. Diagram of the chief peculiarities of ridges,
  called here _minutiæ_ (the scale is about eight times the
  natural size)                                                       54

  Fig. 6. The systems of ridges and the creases in the palm,
  indicated respectively by continuous and by dotted lines. Nos.
  2, 3, 4, and 5 show variations in the boundaries of the systems
  of ridges, and places where smaller systems are sometimes
  interpolated                                                        54

  IV.--Fig. 7. The effects of scars and cuts on the ridges: _a_
  is the result of a deep ulcer; _b_ the finger of a tailor
  (temporarily) scarred by the needle; _c_ the result of a deep
  cut                                                                 59

  Fig. 8. Formation of the interspace: filled in (3) by a loop;
  in (4) by a scroll. The triangular plot or plots are indicated.
  In (1) there is no interspace, but a succession of arches are
  formed, gradually flattening into straight lines                    67

  V.--Fig. 9. Specimens of rolled thumb prints, of the natural
  size, in which the patterns have been outlined, p. 69, and on
  which lines have been drawn for orientation and charting            68

  VI.--Fig. 10. Specimens of the outlines of the patterns on the
  ten digits of eight different persons, not selected but taken
  as they came. Its object is to give a general idea of the degree
  of their variety. The supply of ridges from the _inner_ (or
  thumb side) are coloured blue, those from the _outer_ are red
  (the scale is of the natural size)                                  70

  VII.--Fig. 11. Standard patterns of Arches, together with some
  transitional forms, all with their names below                      75

  Fig. 12. As above, with respect to Loops                            75

  VIII.--Fig. 13. As above, with respect to Whorls                    75

  Fig. 14. Cores to Loops, which may consist either of single
  lines, here called _rods_, or of a recurved line or _staple_,
  while the ridges that immediately envelops them is called an
  _envelope_                                                          76

  Fig. 15. Cores to Whorls                                            77

  IX.--Fig. 15. Transitional patterns, enlarged three times,
  between Arches and either Loops or Whorls                           79

  X.--Fig. 16. Transitional patterns, as above, but between Loops
  and Whorls                                                          79

  XI.--Fig. 17. Diagram showing the nine genera formed by the
  corresponding combinations of the two letters by which they are
  expressed, each being _i_, _j_, or _o_ as the case may be. The
  first two diagrams are Arches, and not strictly patterns at all,
  but may with some justice be symbolised by _jj_                     80

  Fig. 18. Ambiguities in minutiæ, showing that certain details in
  them are not to be trusted, while others are                        92

  XII.--Fig. 19. The illustrations to Purkenje's _Commentatio_.
  They are photo-lithographed from the original, which is not
  clearly printed                                                     86

  XIII.--Fig. 20. Enlarged impressions of the same two fingers
  of V. H. Hd., first when a child of 2-1/2, and subsequently when
  a boy of 15 years of age. The lower pair are interesting from
  containing the unique case of failure of exact coincidence yet
  observed. It is marked A. The numerals indicate the
  correspondences                                                     92

  XIV.--Fig. 21. Contains portions on an enlarged scale of eight
  couplets of finger prints, the first print in each couplet
  having been taken many years before the second, as shown by the
  attached dates. The points of correspondence in each couplet are
  indicated by similar numerals                                       93

  XV.--Fig. 22. The fore-finger of Sir W. J. Herschel as printed
  on two occasions, many years apart (enlarged scale). The numerals
  are here inserted on a plan that has the merit of clearness, but
  some of the lineations are thereby sacrificed                       95

  Fig. 23. Shows the periods of life over which the evidence of
  identity extends in Figs 20-22. [By an oversight, not perceived
  until too late for remedy, the bottom line begins at æt. 62
  instead of 67]                                                      97




CHAPTER I

INTRODUCTION


The palms of the hands and the soles of the feet are covered with two
totally distinct classes of marks. The most conspicuous are the creases or
folds of the skin which interest the followers of palmistry, but which are
no more significant to others than the creases in old clothes; they show
the lines of most frequent flexure, and nothing more. The least
conspicuous marks, but the most numerous by far, are the so-called
papillary ridges; they form the subject of the present book. If they had
been only twice as large as they are, they would have attracted general
attention and been commented on from the earliest times. Had Dean Swift
known and thought of them, when writing about the Brobdingnags, whom he
constructs on a scale twelve times as great as our own, he would certainly
have made Gulliver express horror at the ribbed fingers of the giants who
handled him. The ridges on their palms would have been as broad as the
thongs of our coach-whips.

Let no one despise the ridges on account of their smallness, for they are
in some respects the most important of all anthropological data. We shall
see that they form patterns, considerable in size and of a curious variety
of shape, whose boundaries can be firmly outlined, and which are little
worlds in themselves. They have the unique merit of retaining all their
peculiarities unchanged throughout life, and afford in consequence an
incomparably surer criterion of identity than any other bodily feature.
They may be made to throw welcome light on some of the most interesting
biological questions of the day, such as heredity, symmetry, correlation,
and the nature of genera and species. A representation of their lineations
is easily secured in a self-recorded form, by inking the fingers in the
way that will be explained, and pressing them on paper. There is no
prejudice to be overcome in procuring these most trustworthy sign-manuals,
no vanity to be pacified, no untruths to be guarded against.

My attention was first drawn to the ridges in 1888 when preparing a
lecture on Personal Identification for the Royal Institution, which had
for its principal object an account of the anthropometric method of
Bertillon, then newly introduced into the prison administration of France.
Wishing to treat the subject generally, and having a vague knowledge of
the value sometimes assigned to finger marks, I made inquiries, and was
surprised to find, both how much had been done, and how much there
remained to do, before establishing their theoretical value and practical
utility.

Enough was then seen to show that the subject was of real importance, and
I resolved to investigate it; all the more so, as the modern processes of
photographic printing would enable the evidence of such results as might
be arrived at, to be presented to the reader on an enlarged and easily
legible form, and in a trustworthy shape. Those that are put forward in
the following pages, admit of considerable extension and improvement, and
it is only the fact that an account of them seems useful, which causes me
to delay no further before submitting what has thus far been attained, to
the criticism of others.

I have already published the following memoirs upon this subject:

    1. "Personal Identification." _Journal Royal Inst._ 25th May 1888, and
    _Nature_, 28th June 1888.

    2. "Patterns in Thumb and Finger Marks." _Phil. Trans. Royal Society_,
    vol. clxxxii. (1891) b. pp. 1-23. [This almost wholly referred to
    thumb marks.]

    3. "Method of Indexing Finger Marks." _Proc. Royal Society_, vol.
    xlix. (1891).

    4. "Identification by Finger Tips." _Nineteenth Century_, August 1891.

This first and introductory chapter contains a brief and orderly summary
of the contents of those that follow.

The second chapter treats of the previous employment of finger prints
among various nations, which has been almost wholly confined to making
daubs, without paying any regard to the delicate lineations with which
this book is alone concerned. Their object was partly superstitious and
partly ceremonial; superstitious, so far as a personal contact between
the finger and the document was supposed to be of mysterious efficacy:
ceremonial, as a formal act whose due performance in the presence of
others could be attested. A few scattered instances are mentioned of
persons who had made finger prints with enough care to show their
lineations, and who had studied them; some few of these had used them as
signatures. Attention is especially drawn to Sir William Herschel, who
brought the method of finger prints into regular official employment when
he was "Collector" or chief administrator of the Hooghly district in
Bengal, and my large indebtedness to him is expressed in this chapter and
in other places.

In the third chapter various methods of making good prints from the
fingers are described at length, and more especially that which I have now
adopted on a somewhat large scale, at my anthropometric laboratory, which,
through the kindness of the authorities of South Kensington, is at present
lodged in the galleries of their Science Collections. There, the ten
digits of both hands of all the persons who come to be measured, are
impressed with clearness and rapidity, and a very large collection of
prints is steadily accumulating, each set being, as we shall see, a
sign-manual that differentiates the person who made it, throughout the
whole of his life, from all the rest of mankind.

Descriptions are also given of various methods of enlarging a finger print
to a convenient size, when it is desired to examine it closely.
Photography is the readiest of all; on the other hand the prism (as in a
camera lucida) has merits of its own, and so has an enlarging pantagraph,
when it is furnished with a small microscope and cross wires to serve as a
pointer.

In the fourth chapter the character and purpose of the ridges, whose
lineations appear in the finger print, are discussed. They have been the
topic of a considerable amount of careful physiological study in late
years, by writers who have investigated their development in early periods
of unborn life, as well as their evolutionary history. They are perfectly
defined in the monkeys, but appear in a much less advanced stage in other
mammalia. Their courses run somewhat independently of the lines of
flexure. They are studded with pores, which are the open mouths of ducts
proceeding from the somewhat deeply-seated glands which secrete
perspiration, so one of their functions is to facilitate the riddance of
that excretion. The ridges increase in height as the skin is thickened by
hard usage, until callosities begin to be formed, which may altogether
hide them. But the way in which they assist the touch and may tend to
neutralise the dulling effect of a thick protective skin, is still
somewhat obscure. They certainly seem to help in the discrimination of the
character of surfaces that are variously rubbed between the fingers.

These preliminary topics having been disposed of, we are free in the fifth
chapter to enter upon the direct course of our inquiry, beginning with a
discussion of the various patterns formed by the lineations. It will be
shown how systems of parallel ridges sweep in bold curves across the
palmar surface of the hand, and how, whenever the boundaries of two
systems diverge, the interspace is filled up by a compact little system of
its own, variously curved or whorled, having a fictitious resemblance to
an eddy between two currents. An interspace of this kind is found in the
bulb of each finger. The ridges run in parallel lines across the finger,
up to its last joint, beyond which the insertion of the finger-nail causes
a compression of the ridges on either side; their intermediate courses are
in consequence so much broadened out that they commonly separate, and form
two systems with an interspace between them. The independent patterns that
appear in this interspace upon the bulbs of the fingers, are those with
which this book is chiefly concerned.

At first sight, the maze formed by the minute lineations is bewildering,
but it is shown that every interspace can be surely outlined, and when
this is done, the character of the pattern it encloses, starts
conspicuously into view. Examples are given to show how the outlining is
performed, and others in which the outlines alone are taken into
consideration. The cores of the patterns are also characteristic, and are
described separately. It is they alone that have attracted the notice of
previous inquirers. The outlines fall for the most part into nine distinct
genera, defined by the relative directions of the divergent ridges that
enclose them. The upper pair (those that run towards the finger-tip) may
unite, or one or other of them may surmount the other, thus making three
possibilities. There are three similar possibilities in respect to the
lower pair; so, as any one of the first group may be combined with any one
of the second, there are 3 × 3, or nine possibilities in all. The practice
of somewhat rolling the finger when printing from it, is necessary in
order to impress enough of its surface to ensure that the points at which
the boundaries of the pattern begin to diverge, shall be always included.

Plates are given of the principal varieties of patterns, having regard
only to their more fundamental differences, and names are attached for the
convenience of description; specimens are also given of the outlines of
the patterns in all the ten digits of eight different persons, taken at
hazard, to afford a first idea of the character of the material to be
dealt with. Another and less minute system of classification under three
heads is then described, which is very useful for rough preliminary
purposes, and of which frequent use is made further on. It is into Arches,
Loops, and Whorls. In the Arches, there is no pattern strictly speaking,
for there is no interspace; the need for it being avoided by a successive
and regular broadening out of the ridges as they cross the bulb of the
finger. In Loops, the interspace is filled with a system of ridges that
bends back upon itself, and in which no one ridge turns through a complete
circle. Whorls contain all cases in which at least one ridge turns through
a complete circle, and they include certain double patterns which have a
whorled appearance. The transitional cases are few; they are fully
described, pictured, and classified. One great advantage of the rude A.
L. W. system is that it can be applied, with little risk of error, to
impressions that are smudged or imperfect; it is therefore very useful so
far as it goes. Thus it can be easily applied to my own finger prints on
the title-page, made as they are from digits that are creased and
roughened by seventy years of life, and whose impressions have been
closely clipped in order to fit them into a limited space.

A third method of classification is determined by the origin of the ridges
which supply the interspace, whether it be from the thumb side or the
little-finger side; in other words, from the Inner or the Outer side.

Lastly, a translation from the Latin is given of the famous Thesis or
_Commentatio_ of Purkenje, delivered at the University of Breslau in 1823,
together with his illustrations. It is a very rare pamphlet, and has the
great merit of having first drawn attention to the patterns and attempted
to classify them.

In the sixth chapter we reach the question of Persistence: whether or no
the patterns are so durable as to afford a sure basis for identification.
The answer was different from what had been expected. So far as the
proportions of the patterns go, they are _not_ absolutely fixed, even in
the adult, inasmuch as they change with the shape of the finger. If the
finger is plumped out or emaciated, or variously deformed by usage, gout,
or age, the proportions of the pattern will vary also. Two prints of the
same finger, one taken before and the other after an interval of many
years, cannot be expected to be as closely alike as two prints similarly
made from the same woodcut. They are far from satisfying the shrewd test
of the stereoscope, which shows if there has been an alteration even of a
letter in two otherwise duplicate pages of print. The measurements vary at
different periods, even in the adult, just as much if not more than his
height, span, and the lengths of his several limbs. On the other hand, the
numerous bifurcations, origins, islands, and enclosures in the ridges that
compose the pattern, are proved to be _almost beyond change_. A comparison
is made between the pattern on a finger, and one on a piece of lace; the
latter may be stretched or shrunk as a whole, but the threads of which it
is made retain their respective peculiarities. The evidence on which these
conclusions are founded is considerable, and almost wholly derived from
the collections made by Sir W. Herschel, who most kindly placed them at my
disposal. They refer to one or more fingers, and in a few instances to the
whole hand, of fifteen different persons. The intervals before and after
which the prints were taken, amount in some cases to thirty years. Some of
them reach from babyhood to boyhood, some from childhood to youth, some
from youth to advanced middle age, one from middle life to incipient old
age. These four stages nearly include the whole of the ordinary life of
man. I have compared altogether some 700 points of reference in these
couplets of impressions, and only found a single instance of discordance,
in which a ridge that was cleft in a child became united in later years.
Photographic enlargements are given in illustration, which include between
them a total of 157 pairs of points of reference, all bearing distinctive
numerals to facilitate comparison and to prove their unchangeableness.
Reference is made to another illustrated publication of mine, which raises
the total number of points compared to 389, all of which were successful,
with the single exception above mentioned. The fact of an almost complete
persistence in the peculiarities of the ridges from birth to death, may
now be considered as determined. They existed before birth, and they
persist after death, until effaced by decomposition.

In the seventh chapter an attempt is made to appraise the evidential value
of finger prints by the common laws of Probability, paying great heed not
to treat variations that are really correlated, as if they were
independent. An artifice is used by which the number of portions is
determined, into which a print may be divided, in each of which the purely
local conditions introduce so much uncertainty, that a guess derived from
a knowledge of the outside conditions is as likely as not to be wrong. A
square of six ridge-intervals in the side was shown by three different
sets of experiments to be larger than required; one of four
ridge-intervals in the side was too small, but one of five ridge-intervals
appeared to be closely correct. A six-ridge interval square was, however,
at first adopted, in order to gain assurance that the error should be on
the safe side. As an ordinary finger print contains about twenty-four of
these squares, the uncertainty in respect to the entire contents of the
pattern _due to this cause alone_, is expressed by a fraction of which the
numerator is 1, and the denominator is 2 multiplied into itself
twenty-four times, which amounts to a number so large that it requires
eight figures to express it.

A further attempt was made to roughly appraise the neglected uncertainties
relating to the outside conditions, but large as they are, they seem much
inferior in their joint effect to the magnitude of that just discussed.

Next it was found possible, by the use of another artifice, to obtain some
idea of the evidential value of identity when two prints agree in all but
one, two, three, or any other number of particulars. This was done by
using the five ridge-interval squares, of which thirty-five may be
considered to go into a single finger print, being about the same as the
number of the bifurcations, origins, and other points of comparison. The
accidental similarity in their numbers enables us to treat them roughly as
equivalent. On this basis the well-known method of binomial calculation is
easily applied, with the general result that, notwithstanding a failure of
evidence in a few points, as to the identity of two sets of prints, each,
say, of three fingers, amply enough evidence would be supplied by the
remainder to prevent any doubt that the two sets of prints were made by
the same person. When a close correspondence exists in respect to all the
ten digits, the thoroughness of the differentiation of each man from all
the rest of the human species is multiplied to an extent far beyond the
capacity of human imagination. There can be no doubt that the evidential
value of identity afforded by prints of two or three of the fingers, is so
great as to render it superfluous to seek confirmation from other sources.

The eighth chapter deals with the frequency with which the several kinds
of patterns appear on the different digits of the same person, severally
and in connection. The subject is a curious one, and the inquiry
establishes unexpected relationships and distinctions between different
fingers and between the two hands, to whose origin there is at present no
clue. The relationships are themselves connected in the following
way;--calling any two digits on one of the hands by the letters A and B
respectively, and the digit on the other hand, that corresponds to B, by
the symbol B1, then the kinship between A and B1 is identical, in a
statistical sense, with the kinship between A and B.

The chief novelty in this chapter is an attempt to classify nearness of
relationship upon a centesimal scale, in which the number of
correspondences due to mere chance counts as 0°, and complete identity as
100°. It seems reasonable to adopt the scale with only slight reservation,
when the average numbers of the Arches, Loops, and Whorls are respectively
the same in the two kinds of digit which are compared together; but when
they differ greatly, there are no means free from objection, of
determining the 100° division of the scale; so the results, if noted at
all, are subject to grave doubt.

Applying this scale, it appears that digits on opposite hands, which bear
the same name, are more nearly related together than digits bearing
different names, in about the proportion of three to two. It seems also,
that of all the digits, none are so nearly related as the middle finger to
the two adjacent ones.

In the ninth chapter, various methods of indexing are discussed and
proposed, by which a set of finger prints may be so described by a few
letters, that it can be easily searched for and found in any large
collection, just as the name of a person is found in a directory. The
procedure adopted, is to apply the Arch-Loop-Whorl classification to all
ten digits, describing each digit in the order in which it is taken, by
the letter _a_, _l_, or _w_, as the case may be, and arranging the results
in alphabetical sequence. The downward direction of the slopes of loops on
the fore-fingers is also taken into account, whether it be towards the
Inner or the Outer side, thus replacing L on the fore-finger by either _i_
or _o_.

Many alternative methods are examined, including both the recognition and
the non-recognition of all sloped patterns. Also the gain in
differentiation, when all the ten digits are catalogued, instead of only a
few of them. There is so much correlation between the different fingers,
and so much peculiarity in each, that theoretical notions of the value of
different methods of classification are of little worth; it is only by
actual trial that the best can be determined. Whatever plan of index be
adopted, many patterns must fall under some few headings and few or no
patterns under others, the former class resembling in that respect the
Smiths, Browns, and other common names that occur in directories. The
general value of the index much depends on the facility with which these
frequent forms can be broken up by sub-classification, the rarer forms
being easily dealt with. This branch of the subject has, however, been but
lightly touched, under the belief that experience with larger collections
than my own, was necessary before it could be treated thoroughly; means
are, however, indicated for breaking up the large battalions, which have
answered well thus far, and seem to admit of considerable extension. Thus,
the number of ridges in a loop (which is by far the commonest pattern) on
any particular finger, at the part of the impression where the ridges are
cut by the axis of the loop, is a fairly definite and effective datum as
well as a simple one; so also is the character of its inmost lineation, or
core.

In the tenth chapter we come to a practical result of the inquiry, namely,
its possible use as a means of differentiating a man from his fellows. In
civil as well as in criminal cases, the need of some such system is shown
to be greatly felt in many of our dependencies; where the features of
natives are distinguished with difficulty; where there is but little
variety of surnames; where there are strong motives for prevarication,
especially connected with land-tenure and pensions, and a proverbial
prevalence of unveracity.

It is also shown that the value to honest men of sure means of
identifying themselves is not so small among civilised nations even in
peace time, as to be disregarded, certainly not in times of war and of
strict passports. But the value to honest men is always great of being
able to identify offenders, whether they be merely deserters or formerly
convicted criminals, and the method of finger prints is shown to be
applicable to that purpose. For aid in searching the registers of a
criminal intelligence bureau, its proper rank is probably a secondary one;
the primary being some form of the already established Bertillon
anthropometric method. Whatever power the latter gives of successfully
searching registers, that power would be multiplied many hundredfold by
the inclusion of finger prints, because their peculiarities are entirely
unconnected with other personal characteristics, as we shall see further
on. A brief account is given in this chapter of the Bertillon system, and
an attempt is made on a small scale to verify its performance, by
analysing five hundred sets of measures made at my own laboratory. These,
combined with the quoted experiences in attempting to identify deserters
in the United States, allow a high value to this method, though not so
high as has been claimed for it, and show the importance of supplementary
means. But whenever two suspected duplicates of measurements, bodily
marks, photographs and finger prints have to be compared, the lineations
of the finger prints would give an incomparably more trustworthy answer to
the question, whether or no the suspicion of their referring to the same
person was justified, than all the rest put together. Besides this, while
measurements and photographs are serviceable only for adults, and even
then under restrictions, the finger prints are available throughout life.
It seems difficult to believe, now that their variety and persistence have
been proved, the means of classifying them worked out, and the method of
rapidly obtaining clear finger prints largely practised at my laboratory
and elsewhere, that our criminal administration can long neglect the use
of such a powerful auxiliary. It requires no higher skill and judgment to
make, register, and hunt out finger prints, than is to be found in
abundance among ordinary clerks. Of course some practice is required
before facility can be gained in reading and recognising them, but not a
few persons of whom I have knowledge, have interested themselves in doing
so, and found no difficulty.

The eleventh chapter treats of Heredity, and affirmatively answers the
question whether patterns are transmissible by descent. The inquiry proved
more troublesome than was expected, on account of the great variety in
patterns and the consequent rarity with which the same pattern, other than
the common Loop, can be expected to appear in relatives. The available
data having been attacked both by the Arch-Loop-Whorl method, and by a
much more elaborate system of classification--described and figured as the
C system, the resemblances between children of either sex, of the same
parents (or more briefly "fraternal" resemblances, as they are here
called, for want of a better term), have been tabulated and discussed. A
batch of twins have also been analysed. Then cases have been treated in
which both parents had the same pattern on corresponding fingers; this
pattern was compared with the pattern on the corresponding finger of the
child. In these and other ways, results were obtained, all testifying to
the conspicuous effect of heredity, and giving results that can be
measured on the centesimal scale already described. But though the
qualitative results are clear, the quantitative are as yet not well
defined, and that part of the inquiry must lie over until a future time,
when I shall have more data and when certain foreseen improvements in the
method of work may perhaps be carried out. There is a decided appearance,
first observed by Mr. F. Howard Collins, of whom I shall again have to
speak, of the influence of the mother being stronger than that of the
father, in transmitting these patterns.

In the twelfth chapter we come to a branch of the subject of which I had
great expectations, that have been falsified, namely, their use in
indicating Race and Temperament. I thought that any hereditary
peculiarities would almost of necessity vary in different races, and that
so fundamental and enduring a feature as the finger markings must in some
way be correlated with temperament.

The races I have chiefly examined are English, most of whom were of the
upper and middle classes; the others chiefly from London board schools;
Welsh, from the purest Welsh-speaking districts of South Wales; Jews from
the large London schools, and Negroes from the territories of the Royal
Niger Company. I have also a collection of Basque prints taken at Cambo,
some twenty miles inland from Biarritz, which, although small, is large
enough to warrant a provisional conclusion. As a first and only an
approximately correct description, the English, Welsh, Jews, Negroes, and
Basques, may all be spoken of as identical in the character of their
finger prints; the same familiar patterns appearing in all of them with
much the same degrees of frequency, the differences between groups of
different races being not larger than those that occasionally occur
between groups of the same race. The Jews have, however, a decidedly
larger proportion of Whorled patterns than other races, and I should have
been tempted to make an assertion about a peculiarity in the Negroes, had
not one of their groups differed greatly from the rest. The task of
examination has been laborious thus far, but it would be much more so to
arrive with correctness at a second and closer approximation to the truth.
It is doubtful at present whether it is worth while to pursue the subject,
except in the case of the Hill tribes of India and a few other peculiarly
diverse races, for the chance of discovering some characteristic and
perhaps a more monkey-like pattern.

Considerable collections of prints of persons belonging to different
classes have been analysed, such as students in science, and students in
arts; farm labourers; men of much culture; and the lowest idiots in the
London district (who are all sent to Darenth Asylum), but I do not, still
as a first approximation, find any decided difference between their finger
prints. The ridges of artists are certainly not more delicate and close
than those of men of quite another stamp.

In Chapter XIII. the question is discussed and answered affirmatively, of
the right of the nine fundamentally differing patterns to be considered as
different genera; also of their more characteristic varieties to rank as
different genera, or species, as the case may be. The chief test applied,
respected the frequency with which the various Loops that occurred on the
thumbs, were found to differ, in successive degrees of difference, from
the central form of all of them; it was found to accord with the
requirements of the well-known law of Frequency of Error, proving the
existence of a central type, from which the departures were, in common
phraseology, accidental. Now all the evidence in the last chapter concurs
in showing that no sensible amount of correlation exists between any of
the patterns on the one hand, and any of the bodily faculties or
characteristics on the other. It would be absurd therefore to assert that
in the struggle for existence, a person with, say, a loop on his right
middle finger has a better chance of survival, or a better chance of early
marriage, than one with an arch. Consequently genera and species are here
seen to be formed without the slightest aid from either Natural or Sexual
Selection, and these finger patterns are apparently the only peculiarity
in which Panmixia, or the effect of promiscuous marriages, admits of being
studied on a large scale. The result of Panmixia in finger markings,
corroborates the arguments I have used in _Natural Inheritance_ and
elsewhere, to show that "organic stability" is the primary factor by which
the distinctions between genera are maintained; consequently, the progress
of evolution is not a smooth and uniform progression, but one that
proceeds by jerks, through successive "sports" (as they are called), some
of them implying considerable organic changes, and each in its turn being
favoured by Natural Selection.

The same word "variation" has been indiscriminately applied to two very
different conceptions, which ought to be clearly distinguished; the one is
that of the "sports" just alluded to, which are changes in the position of
organic stability, and may, through the aid of Natural Selection, become
fresh steps in the onward course of evolution; the other is that of the
Variations proper, which are merely strained conditions of a stable form
of organisation, and not in any way an overthrow of them. Sports do not
blend freely together; variations proper do so. Natural Selection acts
upon variations proper, just as it does upon sports, by preserving the
best to become parents, and eliminating the worst, but its action upon
mere variations can, as I conceive, be of no permanent value to evolution,
because there is a constant tendency in the offspring to "regress" towards
the parental type. The amount and results of this tendency have been
fully established in _Natural Inheritance_. It is there shown, that after
a certain departure from the central typical form has been reached in any
race, a further departure becomes impossible without the aid of these
sports. In the successive generations of such a population, the average
tendency of filial regression towards the racial centre must at length
counterbalance the effects of filial dispersion; consequently the best of
the produce cannot advance beyond the level already attained by the
parents, the rest falling short of it in various degrees.

       *       *       *       *       *

In concluding these introductory remarks, I have to perform the grateful
duty of acknowledging my indebtedness to Mr. F. Howard Collins, who
materially helped me during the past year. He undertook the numerous and
tedious tabulations upon which the chapters on Heredity, and on Races and
Classes, are founded, and he thoroughly revised nearly the whole of my
MS., to the great advantage of the reader of this book.




CHAPTER II

PREVIOUS USE OF FINGER PRINTS


The employment of impressions of the hand or fingers to serve as
sign-manuals will probably be found in every nation of importance, but the
significance attached to them differs. It ranges from a mere superstition
that personal contact is important, up to the conviction of which this
book will furnish assurance, that when they are properly made, they are
incomparably the most sure and unchanging of all forms of signature. The
existence of the superstitious basis is easily noted in children and the
uneducated; it occupies a prominent place in the witchcrafts of
barbarians. The modern witness who swears on the Bible, is made to hold it
and afterwards to kiss it; he who signs a document, touches a seal or
wafer, and declares that "this is my act and deed." Students of the
primitive customs of mankind find abundant instances of the belief, that
personal contact communicates some mysterious essence from the thing
touched to the person who touches it, and _vice versa_; but it is
unnecessary here to enter further into these elementary human reasonings,
which are fully described and discussed by various well-known writers.

The next grade of significance attached to an impression resembles that
which commends itself to the mind of a hunter who is practised in
tracking. He notices whether a footprint he happens to light upon, is
larger or smaller, broader or narrower, or otherwise differs from the
average, in any special peculiarity; he thence draws his inferences as to
the individual who made it. So, when a chief presses his hand smeared with
blood or grime, upon a clean surface, a mark is left in some degree
characteristic of him. It may be that of a broad stumpy hand, or of a long
thin one; it may be large or small; it may even show lines corresponding
to the principal creases of the palm. Such hand prints have been made and
repeated in many semi-civilised nations, and have even been impressed in
vermilion on their State documents, as formerly by the sovereign of Japan.
Though mere smudges, they serve in a slight degree to individualise the
signer, while they are more or less clothed with the superstitious
attributes of personal contact. So far as I can learn, no higher form of
finger printing than this has ever existed, in regular and well-understood
use, in any barbarous or semi-civilised nation. The ridges dealt with in
this book could not be seen at all in such rude prints, much less could
they be utilised as strictly distinctive features. It is possible that
when impressions of the fingers have been made in wax, and used as seals
to documents, they may sometimes have been subjected to minute scrutiny;
but no account has yet reached me of trials in any of their courts of law,
about disputed signatures, in which the identity of the party who was said
to have signed with his finger print, had been established or disproved by
comparing it with a print made by him then and there. The reader need be
troubled with only a few examples, taken out of a considerable collection
of extracts from books and letters, in which prints, or rather daubs of
the above kind, are mentioned.

A good instance of their small real value may be seen in the _Trans. China
Branch of the Royal Asiatic Society_, Part 1, 1847, published at
Hong-Kong, which contains a paper on "Land Tenure in China," by T. Meadows
Taylor, with a deed concerning a sale of land, in facsimile, and its
translation: this ends, "The mother and the son, the sellers, have in the
presence of all the parties, received the price of the land in full,
amounting to sixty-four taels and five mace, in perfect dollars weighed in
scales. _Impression of the finger of the mother, of the maiden name of
Chin._" The impression, as it appears in the woodcut, is roundish in
outline, and was therefore made by the tip and not the bulb of the finger.
Its surface is somewhat mottled, but there is no trace of any ridges.

The native clerks of Bengal give the name of _tipsahi_ to the mark
impressed by illiterate persons who, refusing to make either a X or their
caste-mark, dip their finger into the ink-pot and touch the document. The
tipsahi is not supposed to individualise the signer, it is merely a
personal ceremony performed in the presence of witnesses.


[Illustration: PLATE 1.

FIG. 1. Chinese Coin, Tang Dynasty, about 618 A.D., with nail mark of the
Empress Wen-teh, figured in relief.

FIG. 2. Order on a Camp Sutler, by the officer of a surveying party in New
Mexico. 1882.]


Many impressions of fingers are found on ancient pottery, as on Roman
tiles; indeed the Latin word _palmatus_ is said to mean an impression in
soft clay, such as a mark upon a wall, stamped by a blow with the palm.
Nail-marks are used ornamentally by potters of various nations. They exist
on Assyrian bricks as signatures; for instance, in the Assyrian room of
the British Museum, on the west side of the case C 43, one of these bricks
contains a notice of sale and is prefaced by words that were translated
for me thus: "Nail-mark of Nabu-sum-usur, the seller of the field, (used)
like his seal." A somewhat amusing incident affected the design of the
Chinese money during the great Tang dynasty, about 618 A.D. A new and
important issue of coinage was to be introduced, and the Secretary of the
Censors himself moulded the design in wax, and humbly submitted it to the
Empress Wen-teh for approval. She, through maladroitness, dug the end of
her enormously long finger-nail into its face, marking it deeply as with a
carpenter's gouge. The poor Secretary of the Censors, Ngeu-yang-siun, who
deserves honour from professional courtiers, suppressing such sentiments
as he must have felt when his work was mauled, accepted the nail-mark of
the Empress as an interesting supplement to the design; he changed it into
a crescent in relief, and the new coins were stamped accordingly. (See
_Coins and Medals_, edited by Stanley Lane Poole, 1885, p. 221.) A
drawing of one of these is given in Plate 1, Fig. 1.

The European practitioners of palmistry and cheiromancy do not seem to
have paid particular attention to the ridges with which we are concerned.
A correspondent of the American Journal _Science_, viii. 166, states,
however, that the Chinese class the striæ at the ends of the fingers into
"pots" when arranged in a coil, and into "hooks." They are also regarded
by the cheiromantists in Japan. A curious account has reached me of
negroes in the United States who, laying great stress on the possession of
finger prints in wax or dough for witchcraft purposes, are also said to
examine their striæ.

Leaving Purkenje to be spoken of in a later chapter, because he deals
chiefly with classification, the first well-known person who appears to
have studied the lineations of the ridges as a means of identification,
was Bewick, who made an impression of his own thumb on a block of wood and
engraved it, as well as an impression of a finger. They were used as
fanciful designs for his illustrated books. Occasional instances of
careful study may also be noted, such as that of Mr. Fauld (_Nature_,
xxii. p. 605, Oct. 28, 1880), who seems to have taken much pains, and that
of Mr. Tabor, the eminent photographer of San Francisco, who, noticing the
lineations of a print that he had accidentally made with his own inked
finger upon a blotting-paper, experimented further, and finally proposed
the method of finger prints for the registration of Chinese, whose
identification has always been a difficulty, and was giving a great deal
of trouble at that particular time; but his proposal dropped through.
Again Mr. Gilbert Thompson, an American geologist, when on Government duty
in 1882 in the wild parts of New Mexico, paid the members of his party by
order of the camp sutler. To guard against forgery he signed his name
across the impression made by his finger upon the order, after first
pressing it on his office pad. He was good enough to send me the duplicate
of one of these cheques made out in favour of a man who bore the ominous
name of "Lying Bob" (Plate 1, Fig. 2). The impression took the place of
the scroll work on an ordinary cheque; it was in violet aniline ink, and
looked decidedly pretty. From time to time sporadic instances like these
are met with, but none are comparable in importance to the regular and
official employment made of finger prints by Sir William Herschel, during
more than a quarter of a century in Bengal. I was exceedingly obliged to
him for much valuable information when first commencing this study, and
have been almost wholly indebted to his kindness for the materials used in
this book for proving the persistence of the lineations throughout life.

Sir William Herschel has presented me with one of the two original
"Contracts" in Bengali, dated 1858, which suggested to his mind the idea
of using this method of identification. It was so difficult to obtain
credence to the signatures of the natives, that he thought he would use
the signature of the hand itself, chiefly with the intention of
frightening the man who made it from afterwards denying his formal act;
however, the impression proved so good that Sir W. Herschel became
convinced that the same method might be further utilised. He finally
introduced the use of finger prints in several departments at Hooghly in
1877, after seventeen years' experience of the value of the evidence they
afforded. A too brief account of his work was given by him in _Nature_,
xxiii. p. 23 (Nov. 25, 1880). He mentions there that he had been taking
finger marks as sign-manuals for more than twenty years, and had
introduced them for practical purposes in several ways in India with
marked benefit. They rendered attempts to repudiate signatures quite
hopeless. Finger prints were taken of Pensioners to prevent their
personation by others after their death; they were used in the office for
Registration of Deeds, and at a gaol where each prisoner had to sign with
his finger. By comparing the prints of persons then living, with their
prints taken twenty years previously, he considered he had proved that the
lapse of at least that period made no change sufficient to affect the
utility of the plan. He informs me that he submitted, in 1877, a report in
semi-official form to the Inspector-General of Gaols, asking to be allowed
to extend the process; but no result followed. In 1881, at the request of
the Governor of the gaol at Greenwich (Sydney), he sent a description of
the method, but no further steps appear to have been taken there.

If the use of finger prints ever becomes of general importance, Sir
William Herschel must be regarded as the first who devised a feasible
method for regular use, and afterwards officially adopted it. His method
of printing for those purposes will be found in the next chapter.




CHAPTER III

METHODS OF PRINTING


It will be the aim of this chapter to show how to make really good and
permanent impressions of the fingers. It is very easy to do so when the
principles of the art are understood and practised, but difficult
otherwise.

One example of the ease of making good, but not permanent impressions, is
found, and should be tried, by pressing the bulb of a finger against
well-polished glass, or against the highly-polished blade of a razor. The
finger must be _very slightly_ oiled, as by passing it through the hair;
if it be moist, dry it with a handkerchief before the oiling. Then press
the bulb of the finger on the glass or razor, as the case may be, and a
beautiful impression will be left. The hardness of the glass or steel
prevents its surface from rising into the furrows under the pressure of
the ridges, while the layer of oil which covers the bottom of the furrows
is too thin to reach down to the glass or steel; consequently the ridges
alone are printed. There is no capillary or other action to spread the
oil, so the impression remains distinct. A merely moist and not oily
finger leaves a similar mark, but it soon evaporates.

This simple method is often convenient for quickly noting the character of
a finger pattern. The impression may be made on a window-pane, a
watch-glass, or even an eye-glass, if nothing better is at hand. The
impression is not seen to its fullest advantage except by means of a
single small source of bright light. The glass or steel has to be so
inclined as just _not_ to reflect the light into the eye. That part of the
light which falls on the oily impression is not so sharply reflected from
it as from the surface of the glass or steel. Consequently some stray
beams of the light which is scattered from the oil, reach the eye, while
all of the light reflected from the highly-polished glass or steel passes
in another direction and is unseen. The result is a brilliantly luminous
impression on a dark background. The impression ceases to be visible when
the glass or steel is not well polished, and itself scatters the light,
like the oil.

There are two diametrically opposed methods of printing, each being the
complement of the other. The method used in ordinary printing, is to ink
the projecting surfaces only, leaving the depressed parts clean. The other
method, used in printing from engraved plates, is to ink the whole
surface, and then to clean the ink from the projecting parts, leaving the
depressions only filled with it. Either of these two courses can be
adopted in taking finger prints, but not the two together, for when they
are combined in equal degrees the result must be a plain black blot.

The following explanations will be almost entirely confined to the first
method, namely, that of ordinary printing, as the second method has so far
not given equally good results.

The ink used may be either printer's ink or water colour, but for
producing the best work, rapidly and on a large scale, the method of
printer's ink seems in every respect preferable. However, water colour
suffices for some purposes, and as there is so much convenience in a pad,
drenched with dye, such as is commonly used for hand stamps, and which is
always ready for use, many may prefer it. The processes with printer's ink
will be described first.

The relief formed by the ridges is low. In the fingers of very young
children, and of some ladies whose hands are rarely submitted to rough
usage, the ridges are exceptionally faint; their crests hardly rise above
the furrows, yet it is the crests only that are to be inked. Consequently
the layer of ink on the slab or pad on which the finger is pressed for the
purpose of blackening it, must be _very thin_. Its thickness must be less
than half the elevation of the ridges, for when the finger is pressed
down, the crests displace the ink immediately below them, and drives it
upwards into the furrows which would otherwise be choked with it.

It is no violent misuse of metaphor to compare the ridges to the crests of
mountain ranges, and the depth of the blackening that they ought to
receive, to that of the newly-fallen snow upon the mountaintops in the
early autumn, when it powders them from above downwards to a
sharply-defined level. The most desirable blackening of the fingers
corresponds to a snowfall which covers all the higher passes, but descends
no lower.

With a finger so inked it is scarcely possible to fail in making a good
imprint; the heaviest pressure cannot spoil it. The first desideratum is,
then, to cover the slab by means of which the finger is to be blackened,
with an extremely thin layer of ink.

This cannot be accomplished with printer's ink unless the slab is very
clean, the ink somewhat fluid, and the roller that is used to spread it,
in good condition. When a plate of glass is used for the slab, it is easy,
by holding the inked slab between the eye and the light, to judge of the
correct amount of inking. It should appear by no means black, but of a
somewhat light brown.

The thickness of ink transferred by the finger to the paper is much less
than that which lay upon the slab. The ink adheres to the slab as well as
to the finger; when they are separated, only a portion of the ink is
removed by the finger. Again, when the inked finger is pressed on the
paper, only a portion of the ink that was on the finger is transferred to
the paper. Owing to this double reduction, it seldom happens that a clear
impression is at the same time black. An ideally perfect material for
blackening would lie loosely on the slab like dust, it would cling very
lightly to the finger, but adhere firmly to the paper.

The last preliminary to be noticed is the slowness with which the
printer's ink hardens on the slab, and the rapidity with which it dries on
paper. While serviceable for hours in the former case, in the latter it
will be dry in a very few seconds. The drying or hardening of this oily
ink has nothing whatever to do with the loss of moisture in the ordinary
sense of the word, that is to say, of the loss of the contained water: it
is wholly due to oxidisation of the oil. An extremely thin oxidised film
soon forms on the surface of the layer on the slab, and this shields the
lower-lying portions of the layer from the air, and retards further
oxidisation. But paper is very unlike a polished slab; it is a fine felt,
full of minute interstices. When a printed period (.) is placed under the
microscope it looks like a drop of tar in the middle of a clean
bird's-nest. The ink is minutely divided among the interstices of the
paper, and a large surface being thereby exposed to the air, it oxidises
at once, while a print from the finger upon glass will not dry for two or
three days. One effect of oxidisation is to give a granulated appearance
to the ink on rollers which have been allowed to get dirty. This
granulation leaves clots on the slab which are fatal to good work:
whenever they are seen, the roller must be cleaned at once.

The best ink for finger printing is not the best for ordinary printing. It
is important to a commercial printer that his ink should dry rapidly on
the paper, and he does not want a particularly thin layer of it;
consequently, he prefers ink that contains various drying materials, such
as litharge, which easily part with their oxygen. In finger prints this
rapid drying is unnecessary, and the drying materials do harm by making
the ink too stiff. The most serviceable ink for our purpose is made of any
pure "drying" oil (or oil that oxidises rapidly), mixed with lampblack and
very little else. I get mine in small collapsible tubes, each holding
about a quarter of an ounce, from Messrs. Reeve & Sons, 113 Cheapside,
London, W.C. Some thousands of fingers may be printed from the contents of
one of these little tubes.

Let us now pass on to descriptions of printing apparatus. First, of that
in regular use at my anthropometric laboratory at South Kensington, which
has acted perfectly for three years; then of a similar but small apparatus
convenient to carry about or send abroad, and of temporary arrangements in
case any part of it may fail. Then lithographic printing will be noticed.
In all these cases some kind of printer's ink has to be used. Next, smoke
prints will be described, which at times are very serviceable; after this
the methods of water colours and aniline dyes; then casts of various
kinds; last of all, enlargements.

_Laboratory apparatus._--Mine consists of: 1, slab; 2, roller; 3, bottle
of benzole (paraffin, turpentine, or solution of washing soda); 4, a
funnel, with blotting-paper to act as a filter; 5, printer's ink; 6, rags
and duster; 7, a small glass dish; 8, cards to print on.

The _Slab_ is a sheet of polished copper, 10-1/2 inches by 7, and about
1/16 inch thick, mounted on a solid board 3/4 inch thick, with projecting
ears for ease of handling. The whole weighs 2-1/2 lbs. Each day it is
cleaned with the benzole and left bright. [A slab of more than double the
length and less than half the width might, as my assistant thinks, answer
better.]

The _Roller_ is an ordinary small-sized printer's roller, 6 inches long
and 3 in diameter, obtained from Messrs. Harrild, 25 Farringdon Street,
London. Mine remained in good condition for quite a year and a half. When
it is worn the maker exchanges it for a new one at a trifling cost. A good
roller is of the highest importance; it affords the only means of
spreading ink evenly and thinly, and with quickness and precision, over a
large surface. The ingenuity of printers during more than four centuries
in all civilised nations, has been directed to invent the most suitable
composition for rollers, with the result that particular mixtures of glue,
treacle, etc., are now in general use, the proportions between the
ingredients differing according to the temperature at which the roller is
intended to be used. The roller, like the slab, is cleansed with benzole
every day (a very rapid process) and then put out of the reach of dust.
Its clean surface is smooth and shining.

The _Benzole_ is kept in a pint bottle. Sometimes paraffin or turpentine
has been used instead; washing soda does not smell, but it dissolves the
ink more slowly. They are otherwise nearly equally effective in cleansing
the rollers and fingers. When dirty, the benzole can be rudely filtered
and used again.

The _Funnel_ holds blotting-paper for filtering the benzole. Where much
printing is going on, and consequent washing of hands, it is worth while
to use a filter, as it saves a little daily expense, though benzole is
very cheap, and a few drops of it will clean a large surface.

The _Ink_ has already been spoken of. The more fluid it is the better, so
long as it does not "run." A thick ink cannot be so thinned by adding
turpentine, etc., as to make it equal to ink that was originally fluid.
The variety of oils used in making ink, and of the added materials, is
endless. For our purpose, any oil that dries and does not spread, such as
boiled or burnt linseed oil, mixed with lampblack, is almost all that is
wanted. The burnt oil is the thicker of the two, and dries the faster.
Unfortunately the two terms, burnt and boiled linseed oil, have no
definite meaning in the trade, boiling or burning not being the simple
processes these words express, but including an admixture of drying
materials, which differ with each manufacturer; moreover, there are two,
if not three, fundamentally distinct qualities of linseed, in respect to
the oil extracted from it. The ink used in the laboratory and described
above, answers all requirements. Many other inks have suited less well;
less even than that which can be made, in a very homely way, with a little
soot off a plate that had been smoked over a candle, mixed with such
boiled linseed oil as can be bought at unpretentious oil and colour shops,
its only fault being a tendency to run.

_Rags_, and a comparatively clean duster, are wanted for cleaning the slab
and roller, without scratching them.

The small _Glass Dish_ holds the benzole, into which the inked fingers are
dipped before wiping them with the duster. Soap and water complete the
preliminary cleansing.

_Cards_, lying flat, and being more easily manipulated than paper, are now
used at the laboratory for receiving the impressions. They are of rather
large size, 11-1/2 × 5 inches, to enable the prints of the ten digits to
be taken on the same card in two rather different ways (see Plate 2, Fig.
3), and to afford space for writing notes. The cards must have a smooth
and yet slightly absorbent surface. If too highly glazed they cease to
absorb, and more ink will remain on the fingers and less be transferred
from them to the paper. A little trial soon determines the best specimen
from among a few likely alternatives. "Correspondence cards" are suitable
for taking prints of not more than three fingers, and are occasionally
employed in the laboratory. Paper books and pads were tried, but their
surfaces are inferior to cards in flatness, and their use is now
abandoned.

The cards should be _very_ white, because, if a photographic enlargement
should at any time be desired, a slight tint on the card will be an
impediment to making a photograph that shall be as sharp in its lines as
an engraving, it being recollected that the cleanest prints are brown, and
therefore not many shades darker than the tints of ordinary cards.

The method of printing at the laboratory is to squeeze a drop or so of ink
on to the slab, and to work it thoroughly with the roller until a thin and
even layer is spread, just as is done by printers, from one of whom a
beginner might well purchase a lesson. The thickness of the layer of ink
is tested from time to time by taking a print of a finger, and comparing
its clearness and blackness with that of a standard print, hung up for the
purpose close at hand. If too much ink has been put on the slab, some of
it must be cleaned off, and the slab rolled afresh with what remains on it
and on the roller. But this fault should seldom be committed; little ink
should be put on at first, and more added little by little, until the
required result is attained.

The right hand of the subject, which should be quite passive, is taken by
the operator, and the bulbs of his four fingers laid flat on the inked
slab and pressed gently but firmly on it by the flattened hand of the
operator. Then the inked fingers are laid flat upon the upper part of the
right-hand side of the card (Plate 2, Fig. 3), and pressed down gently and
firmly, just as before, by the flattened hand of the operator. This
completes the process for one set of prints of the four fingers of the
right hand. Then the bulb of the thumb is slightly _rolled_ on the inked
slab, and again on the lower part of the card, which gives a more extended
but not quite so sharp an impression. Each of the four fingers of the same
hand, in succession, is similarly rolled and impressed. This completes the
process for the second set of prints of the digits of the right hand. Then
the left hand is treated in the same way.

The result is indicated by the diagram, which shows on what parts of the
card the impressions fall. Thus each of the four fingers is impressed
twice, once above with a simple dab, and once below with a rolled
impression, but each thumb is only impressed once; the thumbs being more
troublesome to print from than fingers. Besides, the cards would have to
be made even larger than they are, if two impressions of each thumb had to
be included. It takes from two and a half to three minutes to obtain the
eighteen impressions that are made on each card.

The _pocket apparatus_ is similar to one originally made and used by Sir
William J. Herschel (see Plate 3, Fig. 4, in which the roller and its
bearings are drawn of the same size as those I use). A small cylinder of
hard wood, or of brass tube, say 1-3/4 inch long, and 1/2 or 3/4 inch in
diameter, has a pin firmly driven into each end to serve as an axle. A
piece of tightly-fitting india-rubber tubing is drawn over the cylinder.
The cylinder, thus coated with a soft smooth compressible material, turns
on its axle in two brackets, each secured by screws, as shown in Plate 2,
Fig. 4, to a board (say 6 × 2-1/2 × 1/4 inch) that serves as handle. This
makes a very fair and durable roller; it can be used in the heat and damp
of the tropics, and is none the worse for a wetting, but it is by no means
so good for delicate work as a cylinder covered with roller composition.
These are not at all difficult to make; I have cast them for myself. The
mould is a piece of brass tube, polished inside. A thick disc, with a
central hole for the lower pin of the cylinder, fits smoothly into the
lower end of the mould, and a ring with a thin bar across it, fits over
the other end, the upper pin of the cylinder entering a hole in the middle
of the bar; thus the cylinder is firmly held in the right position. After
slightly oiling the inside of the mould, warming it, inserting the disc
and cylinder, and fitting on the ring, the melted composition is poured in
on either side of the bar. As it contracts on cooling, rather more must be
poured in than at first appears necessary. Finally the roller is pushed
out of the mould by a wooden ramrod, applied to the bottom of the disc.
The composition must be melted like glue, in a vessel surrounded by hot
water, which should never be allowed to boil; otherwise it will be spoilt.
Harrild's best composition is more than twice the cost of that ordinarily
used, and is expensive for large rollers, but for these miniature ones the
cost is unimportant. The mould with which my first roller was made, was an
old pewter squirt with the nozzle cut off; its piston served the double
purpose of disc and ramrod.

The _Slab_ is a piece of thick plate glass, of the same length and width
as the handle to the roller, so they pack up easily together; its edges
are ground to save the fingers and roller alike from being cut. (Porcelain
takes the ink better than glass, but is not to be commonly found in the
shops, of a convenient shape and size; a glazed tile makes a capital
slab.) A collapsible tube of printer's ink, a few rags, and a phial of
washing soda, complete the equipment (benzole may spoil india-rubber).
When using the apparatus, spread a newspaper on the table to prevent
accident, have other pieces of newspaper ready to clean the roller, and to
remove any surplus of ink from it by the simple process of rolling it on
the paper. Take care that the washing soda is in such a position that it
cannot be upset and ruin the polish of the table. With these precautions,
the apparatus may be used with cleanliness even in a drawing-room. The
roller is of course laid on its back when not in use.

My assistant has taken good prints of the three first fingers of the right
hands of more than 300 school children, say 1000 fingers, in a few hours
during the same day, by this apparatus. Hawksley, 357 Oxford Street, W.,
sells a neatly fitted-up box with all the necessary apparatus.

_Rougher arrangements._--A small ball made by tying chamois leather round
soft rags, may be used in the absence of a roller. The fingers are inked
from the ball, over which the ink has been evenly distributed, by dabbing
it many times against a slab or plate. This method gives good results, but
is slow; it would be intolerably tedious to employ it on a large scale, on
all ten digits of many persons.

It is often desirable to obtain finger prints from persons at a distance,
who could not be expected to trouble themselves to acquire the art of
printing for the purpose of making a single finger print. On these
occasions I send folding-cases to them, each consisting of two pieces of
thin copper sheeting, fastened side by side to a slip of pasteboard, by
bending the edges of the copper over it. The pasteboard is half cut
through at the back, along the space between the copper sheets, so that
it can be folded like a reply post-card, the copper sheets being thus
brought face to face, but prevented from touching by the margin of an
interposed card, out of which the middle has been cut away. The two pieces
of copper being inked and folded up, may then be sent by post. On arrival
the ink is fresh, and the folders can be used as ordinary inked slabs.
(See also Smoke Printing, page 47.)

The fluidity of even a very thin layer of ink seems to be retained for an
indefinite time if the air is excluded to prevent oxidisation. I made
experiments, and found that if pieces of glass (photographic quarter
plates) be inked, and placed face to face, separated only by narrow paper
margins, and then wrapped up without other precaution, they will remain
good for a year and a half.

A slight film of oxidisation on the surface of the ink is a merit, not a
harm; it is cleaner to work with and gives a blacker print, because the
ink clings less tenaciously to the finger, consequently more of it is
transferred to the paper.

If a blackened plate becomes dry, and is re-inked without first being
cleaned, the new ink will rob the old of some of its oxygen and it will
become dry in a day or even less.

_Lithography._--Prints may be made on "transfer-paper," and thence
transferred to stone. It is better not to impress the fingers directly
upon the stone, as the print from the stone would be reversed as compared
with the original impression, and mistakes are likely to arise in
consequence. The print is re-reversed, or put right, by impressing the
fingers on transfer-paper. It might sometimes be desirable to obtain
rapidly a large number of impressions of the finger prints of a suspected
person. In this case lithography would be easier, quicker, and cheaper
than photography.

_Water Colours and Dyes._--The pads most commonly used with office stamps
are made of variously prepared gelatine, covered with fine silk to protect
the surface, and saturated with an aniline dye. If the surface be touched,
the finger is inked, and if the circumstances are all favourable, a good
print may be made, but there is much liability to blot. The pad remains
ready for use during many days without any attention, fresh ink being
added at long intervals. The advantage of a dye over an ordinary water
colour is, that it percolates the silk without any of its colour being
kept back; while a solution of lampblack or Indian ink, consisting of
particles of soot suspended in water, leaves all its black particles
behind when it is carefully filtered; only clear water then passes
through.

A serviceable pad may be made out of a few thicknesses of cloth or felt
with fine silk or cambric stretched over it. The ink should be of a slowly
drying sort, made, possibly, of ordinary ink, with the admixture of brown
sugar, honey, glycerine or the like, to bring it to a proper consistence.

Mr. Gilbert Thompson's results by this process have already been
mentioned. A similar process was employed for the Bengal finger prints by
Sir W. Herschel, who sent me the following account: "As to the printing
of the fingers themselves, no doubt practice makes perfect. But I took no
pains with my native officials, some dozen or so of whom learnt to do it
quite well enough for all practical purposes from Bengali written
instructions, and using nothing but a kind of lampblack ink made by the
native orderly for use with the office seal." A batch of these
impressions, which he was so good as to send me, are all clear, and in
most cases very good indeed. It would be easier to employ this method in a
very damp climate than in England, where a very thin layer of lampblack is
apt to dry too quickly on the fingers.

_Printing as from Engraved Plates._--Professor Ray Lankester kindly sent
me his method of taking prints with water colours. "You take a watery
brushful or two of the paint and rub it over the hands, rubbing one hand
against the other until they feel sticky. A _thin_ paper (tissue is best)
placed on an oval cushion the shape of the hand, should be ready, and the
hand pressed not too firmly on to it. I enclose a rough sample, done
without a cushion. You require a cushion for the hollow of the hand, and
the paint must be rubbed by the two hands until they feel sticky, not
watery." This is the process of printing from engravings, the ink being
removed from the ridges, and lying in the furrows. Blood can be used in
the same way.

The following is extracted from an article by Dr. Louis Robinson in the
_Nineteenth Century_, May 1892, p. 303:--

    "I found that direct prints of the infant's feet on paper would answer
    much better [than photography]. After trying various methods I found
    that the best results could be got by covering the foot by means of a
    soft stencil brush with a composition of lampblack, soap, syrup, and
    blue-black ink; wiping it gently from heel to toe with a
    smoothly-folded silk handkerchief to remove the superfluous pigment,
    and then applying a moderately flexible paper, supported on a soft
    pad, direct to the foot."

A curious method with paper and ordinary writing ink, lately contrived by
Dr. Forgeot, is analogous to lithography. He has described in one of the
many interesting pamphlets published by the "Laboratoire d'Anthropologie
Criminelle" of Lyon (_Stenheil_, 2 Rue Casimir-Delavigne, Paris), his new
process of rendering visible the previously invisible details of such
faint finger prints as thieves may have left on anything they have
handled, the object being to show how evidence may sometimes be obtained
for their identification. It is well known that pressure of the hand on
the polished surface of glass or metal leaves a latent image very
difficult to destroy, and which may be rendered visible by suitable
applications, but few probably have suspected that this may be the case,
to a considerable degree, with ordinary paper. Dr. Forgeot has shown that
if a slightly greasy hand, such for example as a hand that has just been
passed through the hair, be pressed on clean paper, and if common ink be
afterwards brushed lightly over the paper, it will refuse to lie thickly
on the greasy parts, and that the result will be a very fair picture of
the minute markings on the fingers. He has even used these productions as
negatives, and printed good photographs from them. He has also sent me a
photographic print made from a piece of glass which had been exposed to
the vapour of hydrofluoric acid, after having been touched by a greasy
hand. I have made many trials of his method with considerable success. It
affords a way of obtaining serviceable impressions in the absence of
better means. Dr. Forgeot's pamphlet describes other methods of a
generally similar kind, which he has found to be less good than the above.

_Smoke Printing._--When other apparatus is not at hand, a method of
obtaining very clear impressions is to smoke a plate over a lighted
candle, to press the finger on the blackened surface, and then on an
adhesive one. The following details must, however, be borne in mind: the
plate must not be smoked too much, for the same reason that a slab must
not be inked too much; and the adhesive surface must be only slightly
damped, not wetted, or the impression will be blurred. A crockery plate is
better than glass or metal, as the soot does not adhere to it so tightly,
and it is less liable to crack. Professor Bowditch finds mica (which is
sold at photographic stores in small sheets) to be the best material.
Certainly the smoke comes wholly off the mica on to the parts of the
finger that touch it, and a beautiful negative is left behind, which can
be utilised in the camera better than glass that has been similarly
treated; but it does not serve so well for a plate that is intended to be
kept ready for use in a pocket-book, its softness rendering it too liable
to be scratched. I prefer to keep a slip of very thin copper sheeting in
my pocket-book, with which, and with the gummed back of a postage stamp,
or even the gummed fringe to a sheet of stamps, impressions can easily be
taken. The thin copper quickly cools, and a wax match supplies enough
smoke. The folders spoken of (p. 42) may be smoked instead of being inked,
and are in some cases preferable to carry in the pocket or to send by
post, being so easy to smoke afresh. Luggage labels that are thickly
gummed at the back furnish a good adhesive surface. The fault of gummed
paper lies in the difficulty of damping it without its curling up. The
gummed paper sold by stationers is usually thinner than luggage labels,
and still more difficult to keep flat. Paste rubbed in a very thin layer
over a card makes a surface that holds soot firmly, and one that will not
stick to other surfaces if accidentally moistened. Glue, isinglass, size,
and mucilage, are all suitable. It was my fortune as a boy to receive
rudimentary lessons in drawing from a humble and rather grotesque master.
He confided to me the discovery, which he claimed as his own, that pencil
drawings could be fixed by licking them; and as I write these words, the
image of his broad swab-like tongue performing the operation, and of his
proud eyes gleaming over the drawing he was operating on, come vividly to
remembrance. This reminiscence led me to try whether licking a piece of
paper would give it a sufficiently adhesive surface. It did so. Nay, it
led me a step further, for I took two pieces of paper and licked both.
The dry side of the one was held over the candle as an equivalent to a
plate for collecting soot, being saved by the moisture at the back from
igniting (it had to be licked two or three times during the process), and
the impression was made on the other bit of paper. An ingenious person
determined to succeed in obtaining the record of a finger impression, can
hardly fail altogether under any ordinary circumstances.

Physiologists who are familiar with the revolving cylinder covered with
highly-glazed paper, which is smoked, and then used for the purpose of
recording the delicate movements of a tracer, will have noticed the beauty
of the impression sometimes left by a finger that had accidentally touched
it. They are also well versed in the art of varnishing such impressions to
preserve them in a durable form.

A cake of blacklead (plumbago), such as is sold for blackening grates,
when rubbed on paper leaves a powdery surface that readily blackens the
fingers, and shows the ridges distinctly. A small part of the black comes
off when the fingers are pressed on sticky paper, but I find it difficult
to ensure good prints. The cakes are convenient to carry and cleanly to
handle. Whitening, and still more, whitening mixed with size, may be used
in the same way, but it gathers in the furrows, not on the ridges.

_Casts_ give undoubtedly the most exact representation of the ridges, but
they are difficult and unsatisfactory to examine, puzzling the eye by
showing too conspicuously the variation of their heights, whereas we only
want to know their courses. Again, as casts must be of a uniform colour,
the finer lines are indistinctly seen except in a particular light.
Lastly, they are both cumbrous to preserve and easily broken.

A sealing-wax impression is the simplest and best kind of cast, and the
finger need not be burnt in making it. The plan is to make a considerable
pool of flaming sealing-wax, stirring it well with the still unmelted
piece of the stick, while it is burning. Then blow out the flame and wait
a little, until the upper layer has cooled. Sealing-wax that has been well
aflame takes a long time to harden thoroughly after it has parted with
nearly all its heat. By selecting the proper moment after blowing out the
flame, the wax will be cool enough for the finger to press it without
discomfort, and it will still be sufficiently soft to take a sharp
impression. Dentist's wax, which is far less brittle, is easily worked,
and takes impressions that are nearly as sharp as those of sealing-wax; it
has to be well heated and kneaded, then plunged for a moment in cold water
to chill the surface, and immediately impressed. Gutta-percha can also be
used. The most delicate of all impressions is that left upon a thick clot
of varnish, which has been exposed to the air long enough for a thin film
to have formed over it. The impression is transient, but lingers
sufficiently to be easily photographed. It happened, oddly enough, that a
few days after I had noticed this effect, and had been experimenting upon
it, I heard an interesting memoir "On the Minute Structure of Striped
Muscle, with special allusion to a new method of investigation by means
of 'Impressions' stamped in Collodion," submitted to the Royal Society by
Dr. John Berry Haycraft, in which an analogous method was used to obtain
impressions of delicate microscopic structures.

_Photographs_ are valuable in themselves, and the negatives serve for
subsequent _enlargements_. They are unquestionably accurate, and the
labour of making them being mechanical, may be delegated. If the print be
in printer's ink on white paper, the process is straightforward, first of
obtaining a negative and afterwards photo-prints from it. The importance
of the paper or card used to receive the finger print being quite white,
has already been pointed out. An imprint on white crockery-ware is
beautifully clear. Some of the photographs may be advantageously printed
by the ferro-prussiate process. The paper used for it does not curl when
dry, its texture is good for writing on, and the blue colour of the print
makes handwriting clearly legible, whether it be in ink or in pencil.

Prints on glass have great merits for use as lantern slides, but it must
be recollected that they may take some days to dry, and that when dry the
ink can be only too easily detached from them by water, which insinuates
itself between the dry ink and the glass. Of course they could be
varnished, if the trouble and cost were no objection, and so preserved.
The negative print left on an inked slab, after the finger has touched it,
is sometimes very clear, that on smoked glass better, and on smoked mica
the clearest of all. These have merely to be placed in the enlarging
camera, where the negative image thrown on argento-bromide paper will
yield a positive print. (See p. 90.)

I have made, by hand, many enlargements with a prism (camera lucida), but
it is difficult to enlarge more than five times by means of it. So much
shade is cast by the head that the prism can hardly be used at a less
distance than 3 inches from the print, or one quarter the distance (12
inches) at which a book is usually read, while the paper on which the
drawing is made cannot well be more than 15 inches below the prism; so it
makes an enlargement of (4 × 15)/12 or five-fold. This is a very
convenient method of analysing a pattern, since the lines follow only the
axes of the ridges, as in Plate 3, Fig. 5. The prism and attached
apparatus may be kept permanently mounted, ready for use at any time,
without the trouble of any adjustment.

An enlarging pantagraph has also been of frequent use to me, in which the
cross-wires of a low-power microscope took the place of the pointer. It
has many merits, but its action was not equally free in all directions;
the enlarged traces were consequently jagged, and required subsequent
smoothing.

All hand-made enlargements are tedious to produce, as the total length of
lineations to be followed is considerable. In a single finger print made
by dabbing down the finger, their actual length amounts to about 18
inches; therefore in a five-fold enlargement of the entire print the
pencil has to be carefully directed over five times that distance, or more
than 7 feet.

Large copies of tracings made on transparent paper, either by the Camera
Lucida or by the Pantagraph, are easily printed by the ferro-prussiate
photographic process mentioned above, in the same way that plans are
copied by engineers.




CHAPTER IV

THE RIDGES AND THEIR USES


The palmar surface of the hands and the soles of the feet, both in men and
monkeys, are covered with minute ridges that bear a superficial
resemblance to those made on sand by wind or flowing water. They form
systems which run in bold sweeps, though the courses of the individual
ridges are less regular. Each ridge (Plate 3, Fig. 5) is characterised by
numerous minute peculiarities, called _Minutiæ_ in this book, here
dividing into two, and there uniting with another (_a_, _b_), or it may
divide and almost immediately reunite, enclosing a small circular or
elliptical space (_c_); at other times its beginning or end is markedly
independent (_d_, _e_); lastly, the ridge may be so short as to form a
small island (_f_).

Whenever an interspace is left between the boundaries of different systems
of ridges, it is filled by a small system of its own, which will have some
characteristic shape, and be called a _pattern_ in this book.


[Illustration: PLATE 3.

FIG. 5. Characteristic peculiarities in Ridges (about 8 times the natural
size).

FIG. 6. Systems of Ridges, and the Creases in the Palm.]


There are three particularly well-marked systems of ridges in the palm of
the hand marked in Plate 3, Fig. 6, ~1~, as Th, AB, and BC. The system Th
is that which runs over the ball of the thumb and adjacent parts of the
palm. It is bounded by the line _a_ which starts from the middle of the
palm close to the wrist, and sweeps thence round the ball of the thumb to
the edge of the palm on the side of the thumb, which it reaches about half
an inch, more or less, below the base of the fore-finger. The system AB is
bounded towards the thumb by the above line _a_, and towards the little
finger by the line _b_; the latter starts from about the middle of the
little-finger side of the palm, and emerges on the opposite side just
below the fore-finger. Consequently, every ridge that wholly crosses the
palm is found in AB. The system BC is bounded thumbwards by the line _b_,
until that line arrives at a point immediately below the axis of the
fore-finger; there the boundary of BC leaves the line _b_, and skirts the
base of the fore-finger until it reaches the interval which separates the
fore and middle fingers. The upper boundary of BC is the line _c_, which
leaves the little-finger side of the palm at a small distance below the
base of the little finger, and terminates between the fore and middle
fingers. Other systems are found between _c_ and the middle, ring, and
little fingers; they are somewhat more variable than those just described,
as will be seen by comparing the five different palms shown in Fig. 6.

An interesting example of the interpolation of a small and independent
system occurs frequently in the middle of one or other of the systems AB
or BC, at the place where the space covered by the systems of ridges
begins to broaden out very rapidly. There are two ways in which the
necessary supply of ridges makes its appearance, the one is by a series of
successive embranchments (Fig. 6, ~1~), the other is by the insertion of
an independent system, as shown in ~4~, ~5~. Another example of an
interpolated system, but of rarer occurrence, is found in the system Th,
on the ball of the thumb, as seen in ~2~.

Far more definite in position, and complex in lineation, are the small
independent systems which appear on the bulbs of the thumb and fingers.
They are more instructive to study, more easy to classify, and will alone
be discussed in this book.

In the diagram of the hand, Fig. 6, ~1~, the three chief cheiromantic
creases are indicated by dots, but are not numbered. They are made (1) by
the flexure of the thumb, (2) of the four fingers simultaneously, and (3)
of the middle, ring, and little fingers simultaneously, while the
fore-finger remains extended. There is no exact accordance between the
courses of the creases and those of the adjacent ridges, less still do the
former agree with the boundaries of the systems. The accordance is closest
between the crease (1) and the ridges in Th; nevertheless that crease does
not agree with the line _a_, but usually lies considerably within it. The
crease (2) cuts the ridges on either side, at an angle of about 30
degrees. The crease (3) is usually parallel to the ridges between which it
runs, but is often far from accordant with the line _c_. The creases at
the various joints of the thumb and fingers cut the ridges at small
angles, say, very roughly, of 15 degrees.

The supposition is therefore untenable that the courses of the ridges are
wholly determined by the flexures. It appears, however, that the courses
of the ridges and those of the lines of flexure may be in part, but in
part only, due to the action of the same causes.

The fact of the creases of the hand being strongly marked in the
newly-born child, has been considered by some to testify to the archaic
and therefore important character of their origin. The crumpled condition
of the hand of the infant, during some months before its birth, seems to
me, however, quite sufficient to account for the creases.

I possess a few specimens of hand prints of persons taken when children,
and again, after an interval of several years: they show a general
accordance in respect to the creases, but not sufficiently close for
identification.

The ridges on the feet and toes are less complex than those on the hands
and digits, and are less serviceable for present purposes, though equally
interesting to physiologists. Having given but little attention to them
myself, they will not be again referred to.

       *       *       *       *       *

The ridges are studded with minute pores which are the open mouths of the
ducts of the somewhat deeply-seated glands, whose office is to secrete
perspiration: Plate 10, _n_, is a good example of them. The distance
between adjacent pores on the same ridge is, roughly speaking, about half
that which separates the ridges. The lines of a pattern are such as an
artist would draw, if dots had been made on a sheet of paper in positions
corresponding to the several pores, and he endeavoured to connect them by
evenly flowing curves; it would be difficult to draw a pattern under these
conditions, and within definite boundaries, that cannot be matched in a
living hand.

The embryological development of the ridges has been studied by many, but
more especially by Dr. A. Kollmann,[1] whose careful investigations and
bibliography should be consulted by physiologists interested in the
subject. He conceives the ridges to be formed through lateral pressures
between nascent structures.


[Illustration: PLATE 4.

FIG. 7. SCARS AND CUTS, AND THEIR EFFECTS ON THE RIDGES.

FIG. 8. FORMATION OF INTERSPACE AND EXAMPLES OF THE ENCLOSED PATTERNS.]


The ridges are said to be first discernible in the fourth month of
foetal life, and fully formed by the sixth. In babies and children the
delicacy of the ridges is proportionate to the smallness of their stature.
They grow simultaneously with the general growth of the body, and continue
to be sharply defined until old age has set in, when an incipient
disintegration of the texture of the skin spoils, and may largely
obliterate them, as in the finger prints on the title-page. They develop
most in hands that do a moderate amount of work, and they are strongly
developed in the foot, which has the hard work of supporting the weight
of the body. They are, as already mentioned, but faintly developed in the
hands of ladies, rendered delicate by the continual use of gloves and lack
of manual labour, and in idiots of the lowest type who are incapable of
labouring at all. When the skin becomes thin, the ridges simultaneously
subside in height. They are obliterated by the callosities formed on the
hands of labourers and artisans in many trades, by the constant pressure
of their peculiar tools. The ridges on the side of the left fore-finger of
tailors and seamstresses are often temporarily destroyed by the needle; an
instance of this is given in Plate 4, Fig. 7, _b_. Injuries, when they are
sufficiently severe to leave permanent scars, destroy the ridges to that
extent. If a piece of flesh is sliced off, or if an ulcer has eaten so
deeply as to obliterate the perspiratory glands, a white cicatrix, without
pores or ridges, is the result (Fig. 7, _a_). Lesser injuries are not
permanent. My assistant happened to burn his finger rather sharply; the
daily prints he took of it, illustrated the progress of healing in an
interesting manner; finally the ridges were wholly restored. A deep clean
cut leaves a permanent thin mark across the ridges (Fig. 7, _c_),
sometimes without any accompanying puckering; but there is often a
displacement of the ridges on both sides of it, exactly like a "fault" in
stratified rocks. A cut, or other injury that is not a clean incision,
leaves a scar with puckerings on all sides, as in Fig. 7, _a_, making the
ridges at that part undecipherable, even if it does not wholly obliterate
them.

The latest and best investigations on the evolution of the ridges have
been made by Dr. H. Klaatsch.[2] He shows that the earliest appearance in
the Mammalia of structures analogous to ridges is one in which small
eminences occur on the ball of the foot, through which the sweat glands
issue in no particular order. The arrangement of the papillæ into rows,
and the accompanying orderly arrangement of the sweat glands, is a
subsequent stage in evolution. The prehensile tail of the Howling Monkey
serves as a fifth hand, and the naked concave part of the tail, with which
it grasps and holds on to boughs, is furnished with ridges arranged
transversely in beautiful order. The numerous drawings of the hands of
monkeys by Allix[3] may be referred to with advantage.

The uses of the ridges are primarily, as I suppose, to raise the mouths of
the ducts, so that the excretions which they pour out may the more easily
be got rid of; and secondarily, in some obscure way, to assist the sense
of touch. They are said to be moulded upon the subcutaneous papillæ in
such a manner that the ultimate organs of touch, namely, the Pacinian
bodies, etc.--into the variety of which it is unnecessary here to
enter--are more closely congregated under the bases of the ridges than
under the furrows, and it is easy, on those grounds, to make reasonable
guesses how the ridges may assist the sense of touch. They must
concentrate pressures, that would otherwise be spread over the surface
generally, upon the parts which are most richly supplied with the
terminations of nerves. By their means it would become possible to
neutralise the otherwise dulling effect of a thick protective epidermis.
Their existence in transverse ridges on the inner surface of the
prehensile tails of monkeys admits of easy justification from this point
of view. The ridges so disposed cannot prevent the tail from curling, and
they must add materially to its sensitiveness. They seem to produce the
latter effect on the hands of man, for, as the epidermis thickens under
use within moderate limits, so the prominence of the ridges increases.

Supposing the ultimate organs of the sense of touch to be really
congregated more thickly under the ridges than under the furrows--on which
there has been some question--the power of tactile discrimination would
depend very much on the closeness of the ridges. The well-known experiment
with the two points of a pair of compasses, is exactly suited to test the
truth of this. It consists in determining the smallest distance apart, of
the two points, at which their simultaneous pressure conveys the sensation
of a double prick. Those persons in whom the ridge-interval was short
might be expected to perceive the double sensation, while others whose
ridge-interval was wide would only perceive a single one, the distance
apart of the compass points, and the parts touched by them, being the same
in both cases. I was very glad to avail myself of the kind offer of Mr.
E. B. Titchener to make an adequate course of experiments at Professor
Wundt's psycho-physical laboratory at Leipzig, to decide this question. He
had the advantage there of being able to operate on fellow-students who
were themselves skilled in such lines of investigation, so while his own
experience was a considerable safeguard against errors of method, that
safety was reinforced by the fact that his experiments were conducted
under the watchful eyes of competent and critical friends. The result of
the enquiry was decisive. It was proved to demonstration that the fineness
or coarseness of the ridges in different persons had no effect whatever on
the delicacy of their tactile discrimination. Moreover, it made no
difference in the results, whether one or both points of the compass
rested on the ridges or in the furrows.

The width of the ridge-interval is certainly no test of the relative power
of discrimination of the different parts of the same hand, because, while
the ridge-interval is nearly uniform over the whole of the palmar surface,
the least distance between the compass points that gives the sensation of
doubleness is more than four times greater when they are applied to some
parts of the palm than when they are applied to the bulbs of the fingers.

The ridges may subserve another purpose in the act of touch, namely, that
of enabling the character of surfaces to be perceived by the act of
rubbing them with the fingers. We all of us perform this, as it were,
intuitively. It is interesting to ask a person who is ignorant of the
real intention, to shut his eyes and to ascertain as well as he can by the
sense of touch alone, the material of which any object is made that is
afterwards put into his hands. He will be observed to explore it very
carefully by rubbing its surface in many directions, and with many degrees
of pressure. The ridges engage themselves with the roughness of the
surface, and greatly help in calling forth the required sensation, which
is that of a thrill; usually faint, but always to be perceived when the
sensation is analysed, and which becomes very distinct when the
indentations are at equal distances apart, as in a file or in velvet. A
thrill is analogous to a musical note, and the characteristics to the
sense of touch, of different surfaces when they are rubbed by the fingers,
may be compared to different qualities of sound or noise. There are,
however, no pure over-tones in the case of touch, as there are in nearly
all sounds.




CHAPTER V

PATTERNS: THEIR OUTLINES AND CORES


The patterns on the thumb and fingers were first discussed at length by
Purkenje in 1823, in a University Thesis or _Commentatio_. I have
translated the part that chiefly concerns us, and appended it to this
chapter together with his corresponding illustrations. Subsequent writers
have adopted his standard types, diminishing or adding to their number as
the case may be, and guided as he had been, by the superficial appearance
of the lineations.

In my earlier trials some three years ago, an attempt at classification
was made upon that same principle, when the experience gained was
instructive. It had seemed best to limit them to the prints of a single
digit, and the thumb was selected. I collected enough specimens to fill
fourteen sheets, containing in the aggregate 504 prints of right thumbs,
arranged in six lines and six columns (6 × 6 × 14 = 504), and another set
of fourteen sheets containing the corresponding left thumbs. Then, for the
greater convenience of study these sheets were photographed, and
enlargements upon paper to about two and a half times the natural size
made from the negatives. The enlargements of the right thumb prints were
reversed, in order to make them comparable on equal terms with those of
the left. The sheets were then cut up into rectangles about the size of
small playing-cards, each of which contained a single print, and the
register number in my catalogue was entered on its back, together with the
letters L. for left, or R.R. for reversed right, as the case might be.

On trying to sort them according to Purkenje's standards, I failed
completely, and many analogous plans were attempted without success. Next
I endeavoured to sort the patterns into groups so that the central pattern
of each group should differ by a unit of "equally discernible difference"
from the central patterns of the adjacent groups, proposing to adopt those
central patterns as standards of reference. After tedious re-sortings,
some sixty standards were provisionally selected, and the whole laid by
for a few days. On returning to the work with a fresh mind, it was painful
to find how greatly my judgment had changed in the interim, and how faulty
a classification that seemed tolerably good a week before, looked then.
Moreover, I suffered the shame and humiliation of discovering that the
identity of certain duplicates had been overlooked, and that one print had
been mistaken for another. Repeated trials of the same kind made it
certain that finality would never be reached by the path hitherto
pursued.

On considering the causes of these doubts and blunders, different
influences were found to produce them, any one of which was sufficient by
itself to give rise to serious uncertainty. A complex pattern is capable
of suggesting various readings, as the figuring on a wall-paper may
suggest a variety of forms and faces to those who have such fancies. The
number of illusive renderings of prints taken from the same finger, is
greatly increased by such trifles as the relative breadths of their
respective lineations and the differences in their depths of tint. The
ridges themselves are soft in substance, and of various heights, so that a
small difference in the pressure applied, or in the quantity of ink used,
may considerably affect the width of the lines and the darkness of
portions of the print. Certain ridges may thereby catch the attention at
one time, though not at others, and give a bias to some false conception
of the pattern. Again, it seldom happens that different impressions of the
same digit are printed from exactly the same part of it, consequently the
portion of the pattern that supplies the dominant character will often be
quite different in the two prints. Hence the eye is apt to be deceived
when it is guided merely by the general appearance. A third cause of error
is still more serious; it is that patterns, especially those of a spiral
form, may be apparently similar, yet fundamentally unlike, the unaided eye
being frequently unable to analyse them and to discern real differences.
Besides all this, the judgment is distracted by the mere size of the
pattern, which catches the attention at once, and by other secondary
matters such as the number of turns in the whorled patterns, and the
relative dimensions of their different parts. The first need to be
satisfied, before it could become possible to base the classification upon
a more sure foundation than that of general appearance, was to establish a
well-defined point or points of reference in the patterns. This was done
by utilising the centres of the one or two triangular plots (see Plate 4,
Fig. 8, ~2~, ~3~, ~4~) which are found in the great majority of patterns,
and whose existence was pointed out by Purkenje, but not their more remote
cause, which is as follows:

The ridges, as was shown in the diagram (Plate 3) of the palm of the hand,
run athwart the fingers in rudely parallel lines up to the last joint, and
if it were not for the finger-nail, would apparently continue parallel up
to the extreme finger-tip. But the presence of the nail disturbs their
parallelism and squeezes them downwards on both sides of the finger. (See
Fig. 8, ~2~.) Consequently, the ridges that run close to the tip are
greatly arched, those that successively follow are gradually less arched
until, in some cases, all signs of the arch disappear at about the level
of the first joint (Fig. 8, ~1~). Usually, however, this gradual
transition from an arch to a straight line fails to be carried out,
causing a break in the orderly sequence, and a consequent interspace (Fig.
8, ~2~). The topmost boundary of the interspace is formed by the lowermost
arch, and its lowermost boundary by the topmost straight ridge. But an
equally large number of ducts exist within the interspace, as are to be
found in adjacent areas of equal size, whose mouths require to be
supported and connected. This is effected by the interpolation of an
independent system of ridges arranged in loops (Fig. 8, ~3~; also Plate 5,
Fig. 9, _a_, _f_), or in scrolls (Fig. 8, ~4~; also Fig. 9, _g_, _h_), and
this interpolated system forms the "pattern." Now the existence of an
interspace implies the divergence of two previously adjacent ridges (Fig.
8, ~2~), in order to embrace it. Just in front of the place where the
divergence begins, and before the sweep of the pattern is reached, there
are usually one or more very short cross-ridges. Their effect is to
complete the enclosure of the minute triangular plot in question. Where
there is a plot on both sides of the finger, the line that connects them
(Fig. 8, ~4~) serves as a base line whereby the pattern may be oriented,
and the position of any point roughly charted. Where there is a plot on
only one side of the finger (Fig. 8, ~3~), the pattern has almost
necessarily an axis, which serves for orientation, and the pattern can
still be charted, though on a different principle, by dropping a
perpendicular from the plot on to the axis, in the way there shown.

These plots form corner-stones to my system of outlining and subsequent
classification; it is therefore extremely important that a sufficient area
of the finger should be printed to include them. This can always be done
by slightly _rolling_ the finger (p. 39), the result being, in the
language of map-makers, a cylindrical projection of the finger (see Plate
5, Fig. 9, _a-h_). Large as these impressions look, they are of the
natural size, taken from ordinary thumbs.


[Illustration: PLATE 5.

FIG. 9. EXAMPLES OF OUTLINED PATTERNS (The Specimens are rolled
impressions of natural size).]


_The outlines._--The next step is to give a clear and definite shape to
the pattern by drawing its outline (Fig. 9). Take a fine pen, pencil, or
paint brush, and follow in succession each of the two diverging ridges
that start from either plot. The course of each ridge must be followed
with scrupulous conscientiousness, marking it with a clean line as far as
it can be traced. If the ridge bifurcates, always follow the branch that
trends towards the middle of the pattern. If it stops short, let the
outline stop short also, and recommence on a fresh ridge, choosing that
which to the best of the judgment prolongs the course of the one that
stopped. These outlines have an extraordinary effect in making finger
markings intelligible to an untrained eye. What seemed before to be a
vague and bewildering maze of lineations over which the glance wandered
distractedly, seeking in vain for a point on which to fix itself, now
suddenly assumes the shape of a sharply-defined figure. Whatever
difficulties may arise in classifying these figures, they are as nothing
compared to those experienced in attempting to classify unoutlined
patterns, the outlines giving a precision to their general features which
was wanting before.

After a pattern has been treated in this way, there is no further occasion
to pore minutely into the finger print, in order to classify it correctly,
for the bold firm curves of the outline are even more distinct than the
largest capital letters in the title-page of a book.

A fair idea of the way in which the patterns are distributed, is given by
Plate 6. Eight persons were taken in the order in which they happened to
present themselves, and Plate 6 shows the result. For greater clearness,
colour has been employed to distinguish between the ridges that are
supplied from the inner and outer sides of the hand respectively. The
words right and left _must be avoided_ in speaking of patterns, for the
two hands are symmetrically disposed, only in a reversed sense. The right
hand does not look like a left hand, but like the reflection of a left
hand in a looking-glass, and _vice versa_. The phrases we shall employ
will be the _Inner_ and the _Outer_; or thumb-side and little-finger side
(terms which were unfortunately misplaced in my memoir in the _Phil.
Trans._ 1891).

There need be no difficulty in remembering the meaning of these terms, if
we bear in mind that the great toes are undoubtedly innermost; that if we
walked on all fours as children do, and as our remote ancestors probably
did, the thumbs also would be innermost, as is the case when the two hands
are impressed side by side on paper. Inner and outer are better than
thumb-side and little-finger side, because the latter cannot be applied to
the thumbs and little fingers themselves. The anatomical words radial and
ulnar referring to the two bones of the fore-arm, are not in popular use,
and they might be similarly inappropriate, for it would sound oddly to
speak of the radial side of the radius.


[Illustration: PLATE 6.

FIG. 10. OUTLINES OF THE PATTERNS OF THE DIGITS OF EIGHT PERSONS, TAKEN AT
RANDOM.]


The two plots just described will therefore be henceforth designated as
the Inner and the Outer plots respectively, and symbolised by the letters
I and O.

The system of ridges in Fig. 10 that comes from the inner side "I" are
coloured blue; those from the outer "O" are coloured red. The employment
of colour instead of variously stippled surfaces is of conspicuous
advantage to the great majority of persons, though unhappily nearly
useless to about one man in every twenty-five, who is constitutionally
colour-blind.

It may be convenient when marking finger prints with letters for
reference, to use those that look alike, both in a direct and in a
reversed aspect, as they may require to be read either way. The print is a
reversed picture of the pattern upon the digit that made it. The pattern
on one hand is, as already said, a reversed picture of a similar pattern
as it shows on the other. In the various processes by which prints are
multiplied, the patterns may be reversed and re-reversed. Thus, if a
finger is impressed on a lithographic stone, the impressions from that
stone are reversals of the impression made by the same finger upon paper.
If made on transfer paper and thence transferred to stone, there is a
re-reversal. There are even more varied possibilities when photography is
employed. It is worth recollecting that there are twelve capital letters
in the English alphabet which, if printed in block type, are unaffected by
being reversed. They are A.H.I.M.O.T.U.V.W.X.Y.Z. Some symbols do the
same, such as, * + - = :. These and the letters H.O.I.X. have the
further peculiarity of appearing unaltered when upside down.

_Lenses._--As a rule, only a small magnifying power is needed for drawing
outlines, sufficient to allow the eye to be brought within six inches of
the paper, for it is only at that short distance that the _minutiæ_ of a
full-sized finger print begin to be clearly discerned. Persons with normal
sight, during their childhood and boy- or girlhood, are able to read as
closely as this without using a lens, the range in adjustment of the focus
of the eye being then large. But as age advances the range contracts, and
an elderly person with otherwise normal eyesight requires glasses to read
a book even at twelve inches from his eye. I now require much optical aid;
when reading a book, spectacles of 12-inch focus are necessary; and when
studying a finger print, 12-inch eye-glasses in addition, the double power
enabling me to see clearly at a distance of only six inches. Perhaps the
most convenient focus for a lens in ordinary use is 3 inches. It should be
mounted at the end of a long arm that can easily be pushed in any
direction, sideways, backwards, forwards, and up or down. It is
undesirable to use a higher power than this unless it is necessary,
because the field of view becomes narrowed to an inconvenient degree, and
the nearer the head is to the paper, the darker is the shadow that it
casts; there is also insufficient room for the use of a pencil.

Every now and then a closer inspection is wanted; for which purpose a
doublet of 1/2-inch focus, standing on three slim legs, answers well.

For studying the markings on the fingers themselves, a small folding lens,
sold at opticians' shops under the name of a "linen tester," is very
convenient. It is so called because it was originally constructed for the
purpose of counting the number of threads in a given space, in a sample of
linen. It is equally well adapted for counting the number of ridges in a
given space.

       *       *       *       *       *

Whoever desires to occupy himself with finger prints, ought to give much
time and practice to drawing outlines of different impressions of the same
digits. His own ten fingers, and those of a few friends, will furnish the
necessary variety of material on which to work. He should not rest
satisfied until he has gained an assurance that all patterns possess
definite figures, which may be latent but are potentially present, and
that the ridges form something more than a nondescript congeries of
ramifications and twists. He should continue to practise until he finds
that the same ridges have been so nearly followed in duplicate
impressions, that even in difficult cases his work will rarely vary more
than a single ridge-interval.

When the triangular plot happens not to be visible, owing to the print
failing to include it, which is often the case when the finger is not
rolled, as is well shown in the prints of my own ten digits on the
title-page, the trend of the ridges so far as they are seen, usually
enables a practised eye to roughly estimate its true position. By means of
this guidance an approximate, but fairly correct, outline can be drawn.
When the habit of judging patterns by their outlines has become familiar,
the eye will trace them for itself without caring to draw them, and will
prefer an unoutlined pattern to work upon, but even then it is essential
now and then to follow the outline with a fine point, say that of a
penknife or a dry pen.

In selecting standard forms of patterns for the convenience of
description, we must be content to disregard a great many of the more
obvious characteristics. For instance, the size of generally similar
patterns in Fig. 10 will be found to vary greatly, but the words large,
medium, or small may be applied to any pattern, so there is no necessity
to draw a standard outline for each size. Similarly as regards the inwards
or outwards slope of patterns, it is needless to print here a separate
standard outline for either slope, and equally unnecessary to print
outlines in duplicate, with reversed titles, for the right and left hands
respectively. The phrase "a simple spiral" conveys a well-defined general
idea, but there are four concrete forms of it (see bottom row of Plate 11,
Fig. 17, _oj_, _jo_, _ij_, _ji_) which admit of being verbally
distinguished. Again the internal proportions of any pattern, say those of
simple spirals, may vary greatly without affecting the fact of their being
simple spirals. They may be wide or narrow at their mouths, they may be
twisted up into a point (Plate 8, Fig. 14, ~52~), or they may run in broad
curls of uniform width (Fig. 14, ~51~, ~54~). Perhaps the best general
rule in selecting standard outlines, is to limit them to such as cannot be
turned into any other by viewing them in an altered aspect, as upside down
or from the back, or by magnifying or deforming them, whether it be
through stretching, shrinking, or puckering any part of them. Subject to
this general rule and to further and more particular descriptions, the
sets (Plates 7 and 8, Figs. 11, 12, 13) will be found to give considerable
help in naming the usual patterns.


[Illustration: PLATE 7.

FIG. 11. ARCHES.

FIG. 12. LOOPS.]


[Illustration: PLATE 8.

FIG. 13. WHORLS. CORES TO LOOPS.

FIG. 14. Rods:--their envelopes are indicated by dots. Staples:--their
envelopes are indicated by dots. Envelopes whether to Rods or
Staples:--here staples only are dotted.

FIG. 15. CORES TO WHORLS.]


It will be observed that they are grouped under the three principal heads
of Arches, Loops, and Whorls, and that under each of these heads some
analogous patterns as ~4~, ~5~, ~7~, ~8~, etc., are introduced and
underlined with the word "see" so and so, and thus noted as really
belonging to one of the other heads. This is done to indicate the
character of the transitional cases that unite respectively the Arches
with the Loops, the Arches with the Whorls, and the Loops with the Whorls.
More will follow in respect to these. The "tented arch" (~3~) is extremely
rare on the thumb; I do not remember ever to have seen it there,
consequently it did not appear in the plate of patterns in the _Phil.
Trans._ which referred to thumbs. On the other hand, the "banded duplex
spiral" (~30~) is common in the thumb, but rare elsewhere. There are some
compound patterns, especially the "spiral in loop" (~21~) and the "circlet
in loop" (~22~), which are as much loops as whorls; but are reckoned as
whorls. The "twinned loop" (~16~) is of more frequent occurrence than
would be supposed from the examination of _dabbed_ impressions, as the
only part of the outer loop then in view resembles outside arches; it is
due to a double separation of the ridges (Plate 4, Fig. 8), and a
consequent double interspace. The "crested loop" (~13~) may sometimes be
regarded as an incipient form of a "duplex spiral" (~29~).

The reader may also refer to Plate 16, which contains what is there called
the C set of standard patterns. They were arranged and used for a special
purpose, as described in Chapter XI. They refer to impressions of the
right hand.

As a variety of Cores, differing in shape and size, may be found within
each of the outlines, it is advisable to describe them separately. Plate
8, Fig. 14 shows a series of the cores of loops, in which the innermost
lineations may be either straight or curved back; in the one case they are
here called rods (~31~ to ~35~); in the other (~36~ to ~42~), staples. The
first of the ridges that envelops the core, whether the core be a rod,
many rods, or a staple, is also shown and named (~43~ to ~48~). None of
the descriptions are intended to apply to more than the _very end_ of the
core, say, from the tip downwards to a distance equal to two average
ridge-intervals in length. If more of the core be taken into account, the
many varieties in their lower parts begin to make description confusing.
In respect to the "parted" staples and envelopes, and those that are
single-eyed, the description may further mention the side on which the
parting or the eye occurs, whether it be the Inner or the Outer.

At the bottom of Fig. 14, ~49-54~, is given a series of rings, spirals,
and plaits, in which nearly all the clearly distinguishable varieties are
included, no regard being paid to the direction of the twist or to the
number of turns. ~49~ is a set of concentric circles, ~50~ of ellipses:
they are rarely so in a strict sense throughout the pattern, usually
breaking away into a more or less spiriform arrangement as in ~51~. A
curious optical effect is connected with the circular forms, which becomes
almost annoying when many specimens are examined in succession. They seem
to be cones standing bodily out from the paper. This singular appearance
becomes still more marked when they are viewed with only one eye; no
stereoscopic guidance then correcting the illusion of their being contour
lines.

Another curious effect is seen in ~53~, which has the appearance of a
plait or overlap; two systems of ridges that roll together, end bluntly,
the end of the one system running right into a hollow curve of the other,
and there stopping short; it seems, at the first glance, to run beneath
it, as if it were a plait. This mode of ending forms a singular contrast
to that shown in ~51~ and ~52~, where the ridges twist themselves into a
point. ~54~ is a deep spiral, sometimes having a large core filled with
upright and nearly parallel lines; occasionally they are bulbous, and
resemble the commoner "monkey" type, see ~35~.

When the direction of twist is described, the language must be
unambiguous: the following are the rules I adopt. The course of the ridge
is always followed _towards_ the _centre_ of the pattern, and not away
from it. Again, the direction of its course when so followed is specified
at the place where it attains its _highest_ point, or that nearest to the
finger-tip; its course at that point must needs be horizontal, and
therefore directed either towards the inner or the outer side.

The amount of twist has a strong tendency to coincide with either one,
two, three, four, or more half-turns, and not to stop short in
intermediate positions. Here are indications of some unknown fundamental
law, analogous apparently to that which causes Loops to be by far the
commonest pattern.

       *       *       *       *       *

The classification into Arches, Loops, and Whorls is based on the degree
of curvature of the ridges, and enables almost any pattern to be sorted
under one or other of those three heads. There are a few ambiguous
patterns, and others which are nondescript, but the former are uncommon
and the latter rare; as these exceptions give little real inconvenience,
the classification works easily and well.

Arches are formed when the ridges run from one side to the other of the
bulb of the digit without making any backward turn or twist. Loops, when
there is a single backward turn, but no twist. Whorls, when there is a
turn through at least one complete circle; they are also considered to
include all duplex spirals.


[Illustration: PLATE 9.

FIG. 15. TRANSITIONAL PATTERNS--ARCHES AND LOOPS (enlarged three times).]


[Illustration: PLATE 10.

FIG. 16. TRANSITIONAL PATTERNS--LOOPS AND WHORLS (enlarged three times).]


The chief theoretical objection to this threefold system of classification
lies in the existence of certain compound patterns, by far the most common
of which are Whorls enclosed within Loops (Plates 7, 8, Fig. 12, ~15~,
~18~, ~19~, and Fig. 13, ~20-23~). They are as much Loops as Whorls, and
properly ought to be relegated to a fourth class. I have not done so, but
called them Whorls, for a practical reason which is cogent. In an
imperfect impression, such as is made by merely dabbing the inked finger
upon paper, the enveloping loop is often too incompletely printed to
enable its existence to be surely ascertained, especially when the
enclosed whorl is so large (Fig. 13, ~23~) that there are only one or two
enveloping ridges to represent the loop. On the other hand, the whorled
character of the core can hardly fail to be recognised. The practical
difficulties lie almost wholly in rightly classifying a few transitional
forms, diagrammatically and roughly expressed in Fig. 11, ~4~, ~5~, and
Fig. 12, ~8~, ~18~, ~19~, with the words "see" so and so written below,
and of which actual examples are given on an enlarged scale in Plates 9
and 10, Figs. 15 and 16. Here Fig. 15, _a_ is an undoubted arch, and _c_
an undoubted nascent loop; but _b_ is transitional between them, though
nearer to a loop than an arch, _d_ may be thought transitional in the same
way, but it has an incipient curl which becomes marked in _e_, while it
has grown into a decided whorl in _f_; _d_ should also be compared with
_j_, which is in some sense a stage towards _k_. _g_ is a nascent
tented-arch, fully developed in _i_, where the pattern as a whole has a
slight slope, but is otherwise fairly symmetrical. In _h_ there is some
want of symmetry, and a tendency to the formation of a loop on the right
side (refer back to Plate 7, Fig. 11, ~4~, and Fig. 12, ~12~); it is a
transitional case between a tented arch and a loop, with most resemblance
to the latter. Plate 10, Fig. 16 illustrates eyed patterns; here _l_ and
_m_ are parts of decided loops; _p_, _q_, and _r_ are decided whorls, but
_n_ is transitional, inclining towards a loop, and _o_ is transitional,
inclining towards a whorl. _s_ is a nascent form of an invaded loop, and
is nearly related to _l_; _t_ and _u_ are decidedly invaded loops.

The Arch-Loop-Whorl, or, more briefly, the A. L. W. system of
classification, while in some degree artificial, is very serviceable for
preliminary statistics, such as are needed to obtain a broad view of the
distribution of the various patterns. A minute subdivision under numerous
heads would necessitate a proportional and somewhat overwhelming amount of
statistical labour. Fifty-four different standard varieties are by no
means an extravagant number, but to treat fifty-four as thoroughly as
three would require eighteen times as much material and labour. Effort is
economised by obtaining broad results from a discussion of the A. L. W.
classes, afterwards verifying or extending them by special inquiries into
a few of the further subdivisions.


[Illustration: PLATE 11.

FIG. 17. ORIGIN OF SUPPLY OF RIDGES TO PATTERNS OF PRINTS OF RIGHT HAND.

FIG. 18. Ambiguities in prints of the Minutiæ.]


The divergent ridges that bound any simple pattern admit of nine, and only
nine, distinct variations in the first part of their course. The bounding
ridge that has attained the summit of any such pattern must have arrived
either from the Inner plot (I), the Outer plot (O), or from both.
Similarly as regards the bounding ridge that lies at the lowest point of
the pattern. Any one of the three former events may occur in connection
with any of the three latter events, so they afford in all 3 × 3, or nine
possible combinations. It is convenient to distinguish them by easily
intelligible symbols. Thus, let _i_ signify a bounding line which starts
from the point I, whether it proceeds to the summit or to the base of the
pattern; let _o_ be a line that similarly proceeds from O, and let _u_ be
a line that unites the two plots I and O, either by summit or by base.
Again, let two symbols be used, of which the first shall always refer to
the summit, and the second to the base of the pattern. Then the nine
possible cases are--_uu_, _ui_, _uo_; _iu_, _ii_, _io_; _ou_, _oi_, _oo_.
The case of the arches is peculiar, but they may be fairly classed under
the symbol _uu_.

This easy method of classification has much power. For example, the four
possible kinds of simple spirals (see the 1st, 2nd, and the 5th and 6th
diagrams in the lowest row of Plate 11, Fig. 17) are wholly determined by
the letters _oj_, _jo_, _ij_, _ji_ respectively. The two forms of duplex
spirals are similarly determined by _oi_ and _io_ (see 4th and 5th
diagrams in the upper row of Fig. 17), the two slopes of loops by _oo_ and
_ii_ (3rd and 4th in the lower row). It also shows very distinctly the
sources whence the streams of ridges proceed that feed the pattern, which
itself affords another basis for classification. The resource against
uncertainty in respect to ambiguous or difficult patterns is to compile a
dictionary of them, with the heads under which it is advisable that they
should severally be classed. It would load these pages too heavily to give
such a dictionary here. Moreover, it ought to be revised by many
experienced eyes, and the time is hardly ripe for this; when it is, it
would be no difficult task, out of the large number of prints of separate
fingers which for instance I possess (some 15,000), to make an adequate
selection, to enlarge them photographically, and finally to print the
results in pairs, the one untouched, the other outlined and classified.

It may be asked why ridges are followed and not furrows, the furrow being
the real boundary between two systems. The reply is, that the ridges are
the easiest to trace; and, as the error through following the ridges
cannot exceed one-half of a ridge-interval, I have been content to
disregard it. I began by tracing furrows, but preferred the ridges after
trial.

_Measurements._--It has been already shown that when both plots are
present (Plate 4, Fig. 8, ~4~), they form the termini of a base line, from
which any part of the pattern may be triangulated, as surveyors would say.
Also, that when only one plot exists (~3~), and the pattern has an axis
(which it necessarily has in all ordinary _ii_ and _oo_ cases), a
perpendicular can be let fall upon that axis, whose intersection with it
will serve as a second point of reference. But our methods must not be too
refined. The centres of the plots are not determinable with real
exactness, and repeated prints from so soft a substance as flesh are
often somewhat dissimilar, the one being more or less broadened out than
the other, owing to unequal pressure. It is therefore well to use such
other more convenient points of reference as the particular pattern may
present. In loops, the intersection of the axis with the summit of the
innermost bend, whether it be a staple or the envelope to a rod (Fig. 14,
second and third rows of diagrams), is a well-defined position. In
spirals, the centre of the pattern is fairly well defined; also a
perpendicular erected from the middle of the base to the outline above and
below (Fig. 8, ~4~) is precise and convenient.

In prints of adults, measurements may be made in absolute units of length,
as in fractions of an inch, or else in millimetres. An average
ridge-interval makes, however, a better unit, being independent of growth;
it is strictly necessary to adopt it in prints made by children, if
present measurements are hereafter to be compared with future ones. The
simplest plan of determining and employing this unit is to count the
number of ridges to the nearest half-ridge, within the space of one-tenth
of an inch, measured along the axis of the finger at and about the point
where it cuts the _summit_ of the outline; then, having already prepared
scales suitable for the various likely numbers, to make the measurements
with the appropriate scale. Thus, if five ridges were crossed by the axis
at that part, in the space of one-tenth of an inch, each unit of the scale
to be used would be one-fiftieth of an inch; if there were four ridges,
each unit of the scale would be one-fortieth of an inch; if six ridges
one-sixtieth, and so forth. There is no theoretical or practical
difficulty, only rough indications being required.

It is unnecessary to describe in detail how the bearings of any point may
be expressed after the fashion of compass bearings, the direction I-O
taking the place of East-West, the uppermost direction that of North, and
the lowermost of South. Little more is practically wanted than to be able
to describe roughly the position of some remarkable feature in the print,
as of an island or an enclosure. A ridge that is characterised by these or
any other marked peculiarity is easily identified by the above means, and
it thereupon serves as an exact basis for the description of other
features.


_Purkenje's "Commentatio."_

Reference has already been made to Purkenje, who has the honour of being
the person who first described the inner scrolls (as distinguished from
the outlines of the patterns) formed by the ridges. He did so in a
University Thesis delivered at Breslau in 1823, entitled _Commentatio de
examine physiologico organi visus et systematis cutanei_ (a physiological
examination of the visual organ and of the cutaneous system). The thesis
is an ill-printed small 8vo pamphlet of fifty-eight pages, written in a
form of Latin that is difficult to translate accurately into free English.
It is, however, of great historical interest and reputation, having been
referred to by nearly all subsequent writers, some of whom there is
reason to suspect never saw it, but contented themselves with quoting a
very small portion at second-hand. No copy of the pamphlet existed in any
public medical library in England, nor in any private one so far as I
could learn; neither could I get a sight of it at some important
continental libraries. One copy was known of it in America. The very
zealous Librarian of the Royal College of Surgeons was so good as to take
much pains at my instance, to procure one: his zeal was happily and
unexpectedly rewarded by success, and the copy is now securely lodged in
the library of the College.

_The Title_

Commentatio de Examine physiologico organi visus et systematis cutanei
quam pro loco in gratioso medicorum ordine rite obtinendo die Dec. 22,
1823. H.X.L.C. publice defendit Johannes Evangelista Purkenje, Med.
doctor, Phys. et Path. Professor publicus ordinarius des. Assumto socio
Guilielmo Kraus Medicinae studioso.

_Translation_, p. 42.

    "Our attention is next engaged by the wonderful arrangement and
    curving of the minute furrows connected with the organ of touch[4] on
    the inner surfaces of the hand and foot, especially on the last
    phalanx of each finger. Some general account of them is always to be
    found in every manual of physiology and anatomy, but in an organ of
    such importance as the human hand, used as it is for very varied
    movements, and especially serviceable to the sense of touch, no
    research, however minute, can fail in yielding some gratifying
    addition to our knowledge of that organ. After numberless
    observations, I have thus far met with nine principal varieties of
    curvature according to which the tactile furrows are disposed upon the
    inner surface of the last phalanx of the fingers. I will describe them
    concisely, and refer to the diagrams for further explanation (see
    Plate 12, Fig. 19).

    1. _Transverse flexures._--The minute furrows starting from the bend
    of the joint, run from one side of the phalanx to the other; at first
    transversely in nearly straight lines, then by degrees they become
    more and more curved towards the middle, until at last they are bent
    into arches that are almost concentric with the circumference of the
    finger.

    2. _Central Longitudinal Stria._--This configuration is nearly the
    same as in 1, the only difference being that a perpendicular stria is
    enclosed within the transverse furrows, as if it were a nucleus.

    3. _Oblique Stria._--A solitary line runs from one or other of the two
    sides of the finger, passing obliquely between the transverse curves
    in 1, and ending near the middle.

    4. _Oblique Sinus._--If this oblique line recurves towards the side
    from which it started, and is accompanied by several others, all
    recurved in the same way, the result is an oblique sinus, more or less
    upright, or horizontal, as the case may be. A junction at its base, of
    minute lines proceeding from either of its sides, forms a triangle.
    This distribution of the furrows, in which an oblique sinus is found,
    is by far the most common, and it may be considered as a special
    characteristic of man; the furrows that are packed in longitudinal
    rows are, on the other hand, peculiar to monkeys. The vertex of the
    oblique sinus is generally inclined towards the radial side of the
    hand, but it must be observed that the contrary is more frequently the
    case in the fore-finger, the vertex there tending towards the ulnar
    side. Scarcely any other configuration is to be found on the toes. The
    ring finger, too, is often marked with one of the more intricate kinds
    of pattern, while the remaining fingers have either the oblique sinus
    or one of the other simpler forms.


[Illustration: PLATE 12.

FIG. 19. THE STANDARD PATTERNS OF PURKENJE.]


    5. _Almond._--Here the oblique sinus, as already described, encloses
    an almond-shaped figure, blunt above, pointed below, and formed of
    concentric furrows.

    6. _Spiral._--When the transverse flexures described in 1 do not pass
    gradually from straight lines into curves, but assume that form
    suddenly with a more rapid divergence, a semicircular space is
    necessarily created, which stands upon the straight and horizontal
    lines below, as it were upon a base. This space is filled by a spiral
    either of a simple or composite form. The term 'simple' spiral is to
    be understood in the usual geometric sense. I call the spiral
    'composite' when it is made up of several lines proceeding from the
    same centre, or of lines branching at intervals and twisted upon
    themselves. At either side, where the spiral is contiguous to the
    place at which the straight and curved lines begin to diverge, in
    order to enclose it, two triangles are formed, just like the single
    one that is formed at the side of the oblique sinus.

    7. _Ellipse_, or _Elliptical Whorl_.--The semicircular space described
    in 6 is here filled with concentric ellipses enclosing a short single
    line in their middle.

    8. _Circle_, or _Circular Whorl_.--Here a single point takes the place
    of the short line mentioned in 7. It is surrounded by a number of
    concentric circles reaching to the ridges that bound the semicircular
    space.

    9. _Double Whorl._--One portion of the transverse lines runs forward
    with a bend and recurves upon itself with a half turn, and is embraced
    by another portion which proceeds from the other side in the same way.
    This produces a doubly twisted figure which is rarely met with except
    on the thumb, fore, and ring fingers. The ends of the curved portions
    may be variously inclined; they may be nearly perpendicular, of
    various degrees of obliquity, or nearly horizontal.

    In all of the forms 6, 7, 8, and 9, triangles may be seen at the
    points where the divergence begins between the transverse and the
    arched lines, and at both sides. On the remaining phalanges, the
    transverse lines proceed diagonally, and are straight or only slightly
    curved."

(He then proceeds to speak of the palm of the hand in men and in
monkeys.)




CHAPTER VI

PERSISTENCE


The evidence that the minutiæ persist throughout life is derived from the
scrutiny and comparison of various duplicate impressions, one of each pair
having been made many years ago, the other recently. Those which I have
studied more or less exhaustively are derived from the digits of fifteen
different persons. In some cases repeated impressions of one finger only
were available; in most cases of two fingers; in some of an entire hand.
Altogether the whole or part of repeated impressions of between twenty and
thirty different digits have been studied. I am indebted to Sir W. J.
Herschel for almost all these valuable data, without which it would have
been impossible to carry on the inquiry. The only other prints are those
of Sir W. G----, who, from curiosity, took impressions of his own fingers
in sealing-wax in 1874, and fortunately happened to preserve them. He was
good enough to make others for me last year, from which photographic
prints were made. The following table gives an analysis of the above data.
It would be well worth while to hunt up and take the present finger
prints of such of the Hindoos as may now be alive, whose impressions were
taken in India by Sir W. J. Herschel, and are still preserved. Many years
must elapse before my own large collection of finger prints will be
available for the purpose of testing persistence during long periods.

The pattern in every distinct finger print, even though it be only a
dabbed impression, contains on a rough average thirty-five different
points of reference, in addition to its general peculiarities of outline
and core. They consist of forkings, beginnings or ends of ridges, islands,
and enclosures. These minute details are by no means peculiar to the
pattern itself, but are distributed with almost equal abundance throughout
the whole palmar surface. In order to make an exhaustive comparison of two
impressions they ought to be photographically enlarged to a size not
smaller than those shown in Plate 15. Two negatives of impressions can
thus be taken side by side on an ordinary quarter-plate, and any number of
photographic prints made from them; but, for still more comfortable
working, a further enlargement is desirable, say by the prism, p. 52. Some
of the prints may be made on ferro-prussiate paper, as already mentioned
pp. 51, 53; they are more convenient by far than prints made by the silver
or by the platinum process.

Having placed the enlarged prints side by side, two or three conspicuous
and convenient points of reference, whether islands, enclosures, or
particularly distinct bifurcations, should be identified and marked. By
their help, the position of the prints should be readjusted, so that they
shall be oriented exactly alike. From each point of reference, in
succession, the spines of the ridges are then to be followed with a fine
pencil, in the two prints alternately, neatly marking each new point of
comparison with a numeral in coloured ink (Plate 13). When both of the
prints are good and clear, this is rapidly done; wherever the impressions
are faulty, there may be many ambiguities requiring patience to unravel.
At first I was timid, and proceeded too hesitatingly when one of the
impressions was indistinct, making short alternate traces. Afterwards on
gaining confidence, I traced boldly, starting from any well-defined point
of reference and not stopping until there were reasonable grounds for
hesitation, and found it easy in this way to trace the unions between
opposite and incompletely printed ends of ridges, and to disentangle many
bad impressions.

An exact correspondence between the _details_ of two minutiæ is of
secondary importance. Thus, the commonest point of reference is a
bifurcation; now the neck or point of divergence of a new ridge is apt to
be a little low, and sometimes fails to take the ink; hence a new ridge
may appear in one of the prints to have an independent origin, and in the
other to be a branch. The _apparent_ origin is therefore of little
importance, the main fact to be attended to is that a new ridge comes into
existence at a particular point; _how_ it came into existence is a
secondary matter. Similarly, an apparently broken ridge may in reality be
due to an imperfectly printed enclosure; and an island in one print may
appear as part of an enclosure in the other. Moreover, this variation in
details may be the effect not only of imperfect inking or printing, but of
disintegration due to old age, which renders the impressions of the ridges
ragged and broken, as in my own finger prints on the title-page.

Plate 11, Fig. 18 explains the nature of the apparent discrepancies better
than a verbal description. In _a_ a new ridge appears to be suddenly
intruded between two adjacent ones, which have separated to make room for
it; but a second print, taken from the same finger, may have the
appearance of either _b_ or _c_, showing that the new ridge is in reality
a fork of one or other of them, the low connecting neck having failed to
leave an impression. The second line of examples shows how an enclosure
which is clearly defined in _d_ may give rise to the appearance of broken
continuity shown in _e_, and how a distinct island _f_ in one of the
prints may be the remnant of an enclosure which is shown in the other.
These remarks are offered as a caution against attaching undue importance
to disaccord in the details of the minutiæ that are found in the same
place in different prints. Usually, however, the distinction between a
fork and the beginning of a new ridge is clear enough; the islands and
enclosures are also mostly well marked.


[Illustration: PLATE 13.

FIG. 20. V. H. H-D æt. 2-1/2 in 1877, and again as a boy in Nov. 1890.]


Plate 13 gives impressions taken from the fingers of a child of 2-1/2
years in 1877, and again in 1890, when a boy of 15. They are enlarged
photographically to the same size, and are therefore on different scales.
The impressions from the baby-hand are not sharp, but sufficiently
distinct for comparison. Every bifurcation, and beginning or ending of a
ridge, common to the two impressions, is marked with a numeral in blue
ink. There is only one island in the present instance, and that is in the
upper pair of prints; it is clearly seen in the right hand print, lying to
the left of the inscribed number 13, but the badness of the left hand
print makes it hardly decipherable, so it is not numbered. There are a
total of twenty-six good points of comparison common to the upper pair of
prints; there are forty-three points in the lower pair, forty-two of which
appear in both, leaving a single point of disagreement; it is marked A on
the fifth ridge counting from the top. Here a bifurcated ridge in the baby
is filled up in the boy. This one exception, small though it be, is in my
experience unique. The total result of the two pairs of prints is to
afford sixty-eight successes and one failure. The student will find it
well worth his while to study these and the following prints step by step,
to satisfy himself of the extraordinarily exact coincidences between the
two members of either of the pairs. Of course the patterns generally must
be the same, if the ridges composing them are exactly alike, and the most
cursory glance shows them to be so.


[Illustration: PLATE 14.

FIG. 21.]


Plate 14, Fig. 21 contains rather less than a quarter of each of eight
pairs that were published in the _Phil. Trans._ memoir above alluded to.
They were there enlarged photographically to twice their natural size,
which was hardly enough, as it did not allow sufficient space for
inserting the necessary reference numbers. Consequently they have been
again considerably enlarged, so much so that it is impossible to put more
than a portion of each on the page. However, what is given suffices. The
omitted portions may be studied in the memoir. The cases of ~1~ and ~2~
are prints of different fingers of the same individual, first as a child 8
years old, and then as a boy of 17. They have been enlarged on the same
scale but not to the same size; so the print of the child includes a
larger proportion of the original impression than that of the boy. It is
therefore only a part of the child's print which is comparable with that
of the boy. The remaining six cases refer to four different men, belonging
to three quite different families, although their surnames happen to have
the same initial, H. They were adults when the first print was made, and
from 26 to 31 years older on the second occasion. There is an exact
agreement throughout between the two members of each of the eight several
couplets.

In the pair 2. A. E. H. Hl., there is an interesting dot at the point ~4~
(being an island it deserved to have had two numbers, one for the
beginning and one for the end). Small as it is, it persists; its growth in
size corresponding to the growth of the child in stature.


[Illustration: PLATE 15.

FIG. 22. RIGHT FOREFINGER OF SIR W. J. H. in 1860 and in 1888.]


FIG. 23. DISTRIBUTION OF THE PERIODS OF LIFE, to which the evidence of
persistency refers.

  +-----------------------------------------------------------------------+
  |         | Age |        | Age  |          Ages, 0--80 years.           |
  |Persons. |  at |Interval|  at  |                                       |
  |         |first|   in   |second|                                       |
  |         |print| years  |print |    10   20   30   40   50   60   70   |
  |------------------------------------|----|----|----|----|----|----|----|
  |  H. H--d|   2 |   13   |  15  |----+--  |    |    |    |    |    |    |
  |         |     |        |      |    |    |    |    |    |    |    |    |
  |  A. H--l|   4 |   12   |  16  | ---+--- |    |    |    |    |    |    |
  |         |     |        |      |    |    |    |    |    |    |    |    |
  |  J. H--l|   8 |   13   |  21  |  --+----+    |    |    |    |    |    |
  |         |     |        |      |    |    |    |    |    |    |    |    |
  |  E. H--l|  10 |   13   |  23  |    |----+--  |    |    |    |    |    |
  |         |     |        |      |    |    |    |    |    |    |    |    |
  |W.J. H--l|  26 |   30   |  56  |    |    |  --+----+----+--  |    |    |
  |         |     |        |      |    |    |    |    |    |    |    |    |
  |R.F. H--n|  26 |   31   |  57  |    |    |  --+----+----+--- |    |    |
  |         |     |        |      |    |    |    |    |    |    |    |    |
  |N.H. T--n|  27 |   28   |  55  |    |    |   -+----+----+--  |    |    |
  |         |     |        |      |    |    |    |    |    |    |    |    |
  |F.H. H--t|  27 |   26   |  53  |    |    |   -+----+----+-   |    |    |
  |         |     |        |      |    |    |    |    |    |    |    |    |
  |  W. G--e|  62 |   17   |  79  |    |    |    |    |    |    |----+----|
  +-----------------------------------------------------------------------+

For the sake of those who are deficient in the colour sense and therefore
hardly able, if at all, to distinguish even the blue numerals in Figs. 20,
21, I give an eleventh example, Plate 15, Fig. 22, printed all in black.
The numerals are here very legible, but space for their insertion had to
be obtained by sacrificing some of the lineations. It is the right
fore-finger of Sir W. Herschel and has been already published twice; first
in the account of my lecture at the Royal Institution, and secondly, in
its present conspicuous form, in my paper in the _Nineteenth Century_. The
number of years that elapsed between the two impressions is thirty-one,
and the prints contain twenty-four points of comparison, all of which will
be seen to agree. I also possess a later print than this, taken in 1890
from the same finger, which tells the same tale.

The final result of the prints in these pages is that they give
photographic enlargements of the whole or portions of eleven couplets
belonging to six different persons, who are members of five unrelated
families, and which contain between them 158 points of comparison, of
which only one failed. Adding the portions of the prints that are omitted
here, but which will be found in the _Phil. Trans._, the material that I
have thus far published contains 389 points of comparison, of which one
failed. The details are given in the annexed table:--

  +-----------------------------------------------------------------------+
  | Order |  Initials. |Digit | Age  |Dates of| Years |   Total points    |
  |  in   |            | of   |  at  |the two |elapsed|  of agreement in  |
  | the   |            |right | date |prints. |between|-------------------|
  | Figs. |            |hand. |  of  |--------|the two|Figs. 20|Figs. 20, |
  |       |            |      |first |        |prints.|and 21. |22, and in|
  |       |            |      |print.|1st  2nd|       |        |Ph. Trans.|
  |-------|------------|------|------|--------|-------|--------|----------|
  |FIG. 20|            |      |      |        |       |        |          |
  |   1.  |V. H. Hd.   |Fore  | 2-1/2| 1877-90|   13  |   26   |    26    |
  |   2.  |V. H. Hd.   |Ring  | 2-1/2| 1877-90|   13  |   42   |    42    |
  |       |            |      |      |        |       |        |          |
  |FIG. 21|            |      |      |        |       |        |          |
  |   1.  |A. E. H. Hl.|Fore  | 8    | 1881-90|    9  |   11   |    33    |
  |   2.  |A. E. H. Hl.|Ring  | 8    | 1881-90|    9  |    5   |    36    |
  |   3.  |N. H. Tn.   |Fore  |28    | 1862-90|   28  |    6   |    27    |
  |   4.  |N. H. Tn.   |Middle|28    | 1862-90|   28  |   10   |    36    |
  |   5.  |F. K. Ht.   |Fore  |28    | 1862-88|   26  |   12   |    55    |
  |   6.  |R. F. Hn.   |Middle|31    | 1859-90|   31  |    6   |    27    |
  |   7.  |W. J. Hl.   |Thumb |30    | 1860-90|   30  |    9   |    50    |
  |   8.  |W. J. Hl.   |Ring  |31    | 1859-90|   31  |    6   |    32    |
  |       |            |      |      |        |       |        |          |
  |FIG. 22|            |      |      |        |       |        |          |
  |   1.  |W. J. Hl.   |Fore  |31    | 1859-90|   31  |   24   |    24    |
  |---------------------------------------------------|--------|----------|
  |                      Total points of agreement    |  157   |   388    |
  |                          Do.      of disagreement |    1   |     1    |
  +-----------------------------------------------------------------------+

It is difficult to give a just estimate of the number of points of
comparison that I have studied in other couplets of prints, because they
were not examined as exhaustively as in these. There were no less than one
hundred and eleven of them in the ball of the thumb of the child V. H.
Hd., besides twenty-five in the imperfect prints of his middle and little
fingers; these alone raise the total of 389 to 525. I must on the whole
have looked for more than 700 points of comparison, and have found
agreement in every single case that was examined, except the one already
mentioned in Fig. 20, of a ridge that was split in the child, but had
closed up some few years later.

The prints in the two plates cover the intervals from childhood to
boyhood, from boyhood to early manhood, from manhood to about the age of
60, and another set--that of Sir W. G.--covers the interval from 67 to 80.
This is clearly expressed by the diagram (Plate 15, Fig. 23). As there is
no sign, except in one case, of change during any one of these four
intervals, which together almost wholly cover the ordinary life of man, we
are justified in inferring that between birth and death there is
absolutely no change in, say, 699 out of 700 of the numerous
characteristics in the markings of the fingers of the same person, such as
can be impressed by them whenever it is desirable to do so. Neither can
there be any change after death, up to the time when the skin perishes
through decomposition; for example, the marks on the fingers of many
Egyptian mummies, and on the paws of stuffed monkeys, still remain
legible. Very good evidence and careful inquiry is thus seen to justify
the popular idea of the persistence of finger markings, that has hitherto
been too rashly jumped at, and which wrongly ascribed the persistence to
the general appearance of the pattern, rather than to the minutiæ it
contains. There appear to be no external bodily characteristics, other
than deep scars and tattoo marks, comparable in their persistence to these
markings, whether they be on the finger, on other parts of the palmar
surface of the hand, or on the sole of the foot. At the same time they are
out of all proportion more numerous than any other measurable features;
about thirty-five of them are situated on the bulb of each of the ten
digits, in addition to more than 100 on the ball of the thumb, which has
not one-fifth of the superficies of the rest of the palmar surface. The
total number of points suitable for comparison on the two hands must
therefore be not less than one thousand and nearer to two; an estimate
which I verified by a rough count on my own hand; similarly in respect to
the feet. The dimensions of the limbs and body alter in the course of
growth and decay; the colour, quantity, and quality of the hair, the tint
and quality of the skin, the number and set of the teeth, the expression
of the features, the gestures, the handwriting, even the eye-colour,
change after many years. There seems no persistence in the visible parts
of the body, except in these minute and hitherto too much disregarded
ridges.

It must be emphasised that it is in the minutiæ, and _not_ in the measured
dimensions of any portion of the pattern, that this remarkable persistence
is observed, not even if the measurements be made in units of a
ridge-interval. The pattern grows simultaneously with the finger, and its
proportions vary with its fatness, leanness, usage, gouty deformation, or
age. But, though the pattern as a whole may become considerably altered in
length or breadth, the number of ridges, their embranchments, and other
minutiæ remain unchanged. So it is with the pattern on a piece of lace.
The piece as a whole may be stretched in this way, or shrunk in that, and
its outline altogether altered; nevertheless every one of the component
threads, and every knot in every thread, can easily be traced and
identified in both. Therefore, in speaking of the persistence of the marks
on the finger, the phrase must be taken to apply principally to the
minutiæ, and to the general character of the pattern; not to the measure
of its length, breadth, or other diameter; these being no more constant
than the stature, or any other of the ordinary anthropometric data.




CHAPTER VII

EVIDENTIAL VALUE


The object of this chapter is to give an approximate numerical idea of the
value of finger prints as a means of Personal Identification. Though the
estimates that will be made are professedly and obviously far below the
truth, they are amply sufficient to prove that the evidence afforded by
finger prints may be trusted in a most remarkable degree.

Our problem is this: given two finger prints, which are alike in their
minutiæ, what is the chance that they were made by different persons?

The first attempt at comparing two finger prints would be directed to a
rough general examination of their respective patterns. If they do not
agree in being arches, loops, or whorls, there can be no doubt that the
prints are those of different fingers, neither can there be doubt when
they are distinct forms of the same general class. But to agree thus far
goes only a short way towards establishing identity, for the number of
patterns that are promptly distinguishable from one another is not large.
My earlier inquiries showed this, when endeavouring to sort the prints of
1000 thumbs into groups that differed each from the rest by an "equally
discernible" interval. While the attempt, as already mentioned, was not
successful in its main object, it showed that nearly all the collection
could be sorted into 100 groups, in each of which the prints had a fairly
near resemblance. Moreover, twelve or fifteen of the groups referred to
different varieties of the loop; and as two-thirds of all the prints are
loops, two-thirds of the 1000 specimens fell into twelve or fifteen
groups. The chance that an unseen pattern is some particular variety of
loop, is therefore compounded of 2 to 3 against its being a loop at all,
and of 1 to 12 or 15, as the case may be, against its being the specified
kind of loop. This makes an adverse chance of only 2 to 36, or to 45, say
as 2 to 40, or as 1 to 20. This very rude calculation suffices to show
that on the average, no great reliance can be placed on a general
resemblance in the appearance of two finger prints, as a proof that they
were made by the same finger, though the obvious disagreement of two
prints is conclusive evidence that they were made by different fingers.

When we proceed to a much more careful comparison, and collate
successively the numerous minutiæ, their coincidence throughout would be
an evidence of identity, whose value we will now try to appraise.

Let us first consider the question, how far may the minutiæ, or groups of
them, be treated as _independent_ variables?

Suppose that a tiny square of paper of only one average ridge-interval in
the side, be cut out and dropped at random on a finger print; it will
mask from view a minute portion of one, or possibly of two ridges. There
can be little doubt that what was hidden could be correctly interpolated
by simply joining the ends of the ridge or ridges that were interrupted.
It is true, the paper might possibly have fallen exactly upon, and hidden,
a minute island or enclosure, and that our reconstruction would have
failed in consequence, but such an accident is improbable in a high
degree, and may be almost ignored.

Repeating the process with a much larger square of paper, say of twelve
ridge-intervals in the side, the improbability of correctly reconstructing
the masked portion will have immensely increased. The number of ridges
that enter the square on any one side will perhaps, as often as not,
differ from the number which emerge from the opposite side; and when they
are the same, it does not at all follow that they would be continuous each
to each, for in so large a space forks and junctions are sure to occur
between some, and it is impossible to know which, of the ridges.
Consequently, there must exist a certain size of square with more than one
and less than twelve ridge-intervals in the side, which will mask so much
of the print, that it will be an even chance whether the hidden portion
can, on the average, be rightly reconstructed or not. The size of that
square must now be considered.

If the reader will refer to Plate 14, in which there are eight much
enlarged photographs of portions of different finger prints, he will
observe that the length of each of the portions exceeds the breadth in
the proportion of 3 to 2. Consequently, by drawing one line down the
middle and two lines across, each portion may be divided into six squares.
Moreover, it will be noticed that the side of each of these squares has a
length of about six ridge-intervals. I cut out squares of paper of this
size, and throwing one of them at random on any one of the eight portions,
succeeded almost as frequently as not in drawing lines on its back which
comparison afterwards showed to have followed the true course of the
ridges. The provisional estimate that a length of six ridge-intervals
approximated to but exceeded that of the side of the desired square,
proved to be correct by the following more exact observations, and by
three different methods.

I. The first set of tests to verify this estimate were made upon
photographic enlargements of various thumb prints, to double their natural
size. A six-ridge-interval square of paper was damped and laid at random
on the print, the core of the pattern, which was too complex in many cases
to serve as an average test, being alone avoided. The prints being on
ordinary albuminised paper, which is slightly adherent when moistened, the
patch stuck temporarily wherever it was placed and pressed down. Next, a
sheet of tracing-paper, which we will call No. 1, was laid over all, and
the margin of the square patch was traced upon it, together with the
course of the surrounding ridges up to that margin. Then I interpolated on
the tracing-paper what seemed to be the most likely course of those ridges
which were hidden by the square. No. 1 was then removed, and a second
sheet, No. 2, was laid on, and the margin of the patch was outlined on it
as before, together with the ridges leading up to it. Next, a corner only
of No. 2 was raised, the square patch was whisked away from underneath,
the corner was replaced, the sheet was flattened down, and the actual
courses of the ridges within the already marked outline were traced in.
Thus there were two tracings of the margin of the square, of which No. 1
contained the ridges as I had interpolated them, No. 2 as they really
were, and it was easy to compare the two. The results are given in the
first column of the following table:--

INTERPOLATION OF RIDGES IN A SIX-RIDGE-INTERVAL SQUARE.

  +---------------------------------------------------------+
  |Result.|   Double    |Six-fold scale| Twenty-fold |Total.|
  |       |Enlargements.| with prism.  |  scale with |      |
  |       |             |              |chequer-work.|      |
  |-------|-------------|--------------|-------------|------|
  |Right  |     12      |      8       |      7      |  27  |
  |Wrong  |     20      |     12       |     16      |  48  |
  |-------|-------------|--------------|-------------|------|
  |Total  |     32      |     20       |     23      |  75  |
  +---------------------------------------------------------+

II. In the second method the tracing-papers were discarded, and the prism
of a camera lucida used. It threw an image three times the size of the
photo-enlargement, upon a card, and there it was traced. The same general
principle was adopted as in the first method, but the results being on a
larger scale, and drawn on stout paper, were more satisfactory and
convenient. They are given in the second column of the table. In this and
the foregoing methods two different portions of the same print were
sometimes dealt with, for it was a little more convenient and seemed as
good a way of obtaining average results as that of always using portions
of different finger prints. The total number of fifty-two trials, by one
or other of the two methods, were made from about forty different prints.
(I am not sure of the exact number.)

The results in each of the two methods were sometimes quite right,
sometimes quite wrong, sometimes neither one nor the other. The latter
depended on the individual judgment as to which class it belonged, and
might be battled over with more or less show of reason by advocates on
opposite sides. Equally dividing these intermediate cases between "right"
and "wrong," the results were obtained as shown. In one, and only one, of
the cases, the most reasonable interpretation had not been given, and the
result had been wrong when it ought to have been right. The purely
personal error was therefore disregarded, and the result entered as
"right."

III. A third attempt was made by a different method, upon the lineations
of a finger print drawn on about a twenty-fold scale. It had first been
enlarged four times by photography, and from this enlargement the axes of
the ridges had been drawn with a five-fold enlarging pantagraph. The aim
now was to reconstruct the entire finger print by two successive and
independent acts of interpolation. A sheet of transparent tracing-paper
was ruled into six-ridge-interval squares, and every one of its alternate
squares was rendered opaque by pasting white paper upon it, giving it the
appearance of a chess-board. When this chequer-work was laid on the print,
exactly one half of the six-ridge squares were masked by the opaque
squares, while the ridges running up to them could be seen. They were not
quite so visible as if each opaque square had been wholly detached from
its neighbours, instead of touching them at the extreme corners, still the
loss of information thereby occasioned was small, and not worth laying
stress upon. It is easily understood that when the chequer-work was moved
parallel to itself, through the space of one square, whether upwards or
downwards, or to the right or left, the parts that were previously masked
became visible, and those that were visible became masked. The object was
to interpolate the ridges in every opaque square under one of these
conditions, then to do the same for the remaining squares under the other
condition, and finally, by combining the results, to obtain a complete
scheme of the ridges wholly by interpolation. This was easily done by
using two sheets of tracing-paper, laid in succession over the
chequer-work, whose position on the print had been changed meanwhile, and
afterwards tracing the lineations that were drawn on one of the two sheets
upon the vacant squares of the other. The results are given in the third
column of the table.

The three methods give roughly similar results, and we may therefore
accept the ratios of their totals, which is 27 to 75, or say 1 to 3, as
representing the chance that the reconstruction of any six-ridge-interval
square would be correct under the given conditions. On reckoning the
chance as 1 to 2, which will be done at first, it is obvious that the
error, whatever it may be, is on the safe side. A closer equality in the
chance that the ridges in a square might run in the observed way or in
some other way, would result from taking a square of five ridge-intervals
in the side. I believe this to be very closely the right size. A
four-ridge-interval square is certainly too small.

When the reconstructed squares were wrong, they had none the less a
natural appearance. This was especially seen, and on a large scale, in the
result of the method by chequer-work, in which the lineations of an entire
print were constructed by guess. Being so familiar with the run of these
ridges in finger prints, I can speak with confidence on this. My
assumption is, that any one of these reconstructions represents lineations
that might have occurred in Nature, in association with the conditions
outside the square, just as well as the lineations of the actual finger
print. The courses of the ridges in each square are subject to
uncertainties, due to petty _local_ incidents, to which the conditions
outside the square give no sure indication. They appear to be in great
part determined by the particular disposition of each one or more of the
half hundred or so sweat-glands which the square contains. The ridges
rarely run in evenly flowing lines, but may be compared to footways across
a broken country, which, while they follow a general direction, are
continually deflected by such trifles as a tuft of grass, a stone, or a
puddle. Even if the number of ridges emerging from a six-ridge-interval
square equals the number of those which enter, it does not follow that
they run across in parallel lines, for there is plenty of room for any one
of the ridges to end, and another to bifurcate. It is impossible,
therefore, to know beforehand in which, if in any of the ridges, these
peculiarities will be found. When the number of entering and issuing
ridges is unequal, the difficulty is increased. There may, moreover, be
islands or enclosures in any particular part of the square. It therefore
seems right to look upon the squares as independent variables, in the
sense that when the surrounding conditions are alone taken into account,
the ridges within their limits may either run in the observed way or in a
different way, the chance of these two contrasted events being taken (for
safety's sake) as approximately equal.

In comparing finger prints which are alike in their general pattern, it
may well happen that the proportions of the patterns differ; one may be
that of a slender boy, the other that of a man whose fingers have been
broadened or deformed by ill-usage. It is therefore requisite to imagine
that only one of the prints is divided into exact squares, and to suppose
that a reticulation has been drawn over the other, in which each mesh
included the corresponding parts of the former print. Frequent trials have
shown that there is no practical difficulty in actually doing this, and
it is the only way of making a fair comparison between the two.

These six-ridge-interval squares may thus be regarded as independent
units, each of which is equally liable to fall into one or other of two
alternative classes, when the surrounding conditions are alone known. The
inevitable consequence from this datum is that the chance of an exact
correspondence between two different finger prints, in each of the
six-ridge-interval squares into which they may be divided, and which are
about 24 in number, is at least as 1 to 2 multiplied into itself 24 times
(usually written 2{24}), that is as 1 to about ten thousand millions. But
we must not forget that the six-ridge square was taken in order to ensure
under-estimation, a five-ridge square would have been preferable, so the
adverse chances would in reality be enormously greater still.

It is hateful to blunder in calculations of adverse chances, by
overlooking correlations between variables, and to falsely assume them
independent, with the result that inflated estimates are made which
require to be proportionately reduced. Here, however, there seems to be
little room for such an error.

We must next combine the above enormously unfavourable chance, which we
will call _a_, with the other chances of not guessing correctly beforehand
the surrounding conditions under which _a_ was calculated. These latter
are divisible into _b_ and _c_; the chance _b_ is that of not guessing
correctly the general course of the ridges adjacent to each square, and
_c_ that of not guessing rightly the number of ridges that enter and
issue from the square. The chance _b_ has already been discussed, with the
result that it might be taken as 1 to 20 for two-thirds of all the
patterns. It would be higher for the remainder, and very high indeed for
some few of them, but as it is advisable always to underestimate, it may
be taken as 1 to 20; or, to obtain the convenience of dealing only with
values of 2 multiplied into itself, the still lower ratio of 1 to 2{4},
that is as 1 to 16. As to the remaining chance _c_ with which _a_ and _b_
have to be compounded, namely, that of guessing aright the number of
ridges that enter and leave each side of a particular square, I can offer
no careful observations. The number of the ridges would for the most part
vary between five and seven, and those in the different squares are
certainly not quite independent of one another. We have already arrived at
such large figures that it is surplusage to heap up more of them,
therefore, let us say, as a mere nominal sum much below the real figure,
that the chance against guessing each and every one of these data
correctly is as 1 to 250, or say 1 to 2{8} (= 256).

The result is, that the chance of lineations, constructed by the
imagination according to strictly natural forms, which shall be found to
resemble those of a single finger print in all their minutiæ, is less than
1 to 2{24} × 2{4} × 2{8}, or 1 to 2{36}, or 1 to about sixty-four thousand
millions. The inference is, that as the number of the human race is
reckoned at about sixteen thousand millions, it is a smaller chance than 1
to 4 that the print of a _single_ finger of any given person would be
exactly like that of the same finger of any other member of the human
race.

When two fingers of each of the two persons are compared, and found to
have the same minutiæ, the improbability of 1 to 2{36} becomes squared,
and reaches a figure altogether beyond the range of the imagination; when
three fingers, it is cubed, and so on.

A single instance has shown that the minutiæ are _not_ invariably
permanent throughout life, but that one or more of them may possibly
change. They may also be destroyed by wounds, and more or less
disintegrated by hard work, disease, or age. Ambiguities will thus arise
in their interpretation, one person asserting a resemblance in respect to
a particular feature, while another asserts dissimilarity. It is therefore
of interest to know how far a conceded resemblance in the great majority
of the minutiæ combined with some doubt as to the remainder, will tell in
favour of identity. It will now be convenient to change our datum from a
six-ridge to a five-ridge square of which about thirty-five are contained
in a single print, 35 × 5{2} or 35 × 25 being much the same as 24 × 6{2}
or 24 × 36. The reason for the change is that this number of thirty-five
happens to be the same as that of the minutiæ. We shall therefore not be
acting unfairly if, with reservation, and for the sake of obtaining some
result, however rough, we consider the thirty-five minutiæ themselves as
so many independent variables, and accept the chance now as 1 to 2{35}.

This has to be multiplied, as before, into the factor of 2{4} × 2{8}
(which may still be considered appropriate, though it is too small),
making the total of adverse chances 1 to 2{47}. Upon such a basis, the
calculation is simple. There would on the average be 47 instances, out of
the total 2{47} combinations, of similarity in all but one particular; (47
× 46)/(1 × 2) in all but two; (47 × 46 × 45)/(1 × 2 × 3) in all but three,
and so on according to the well-known binomial expansion. Taking for
convenience the powers of 2 to which these values approximate, or rather
with the view of not overestimating, let us take the power of 2 that falls
short of each of them; these may be reckoned as respectively equal to
2{6}, 2{10}, 2{14}, 2{18}, etc. Hence the roughly approximate chances of
resemblance in all particulars are as 2{47} to 1; in all particulars but
one, as 2{47-6}, or 2{41} to 1; in all but two, as 2{37} to 1; in all but
three, as 2{33} to 1; in all but four, as 2{29} to 1. Even 2{29} is so
large as to require a row of nine figures to express it. Hence a few
instances of dissimilarity in the two prints of a single finger, still
leave untouched an enormously large residue of evidence in favour of
identity, and when two, three, or more fingers in the two persons agree to
that extent, the strength of the evidence rises by squares, cubes, etc.,
far above the level of that amount of probability which begins to rank as
certainty.

Whatever reductions a legitimate criticism may make in the numerical
results arrived at in this chapter, bearing in mind the occasional
ambiguities pictured in Fig. 18, the broad fact remains, that a complete
or nearly complete accordance between two prints of a single finger, and
vastly more so between the prints of two or more fingers, affords
evidence requiring no corroboration, that the persons from whom they were
made are the same. Let it also be remembered, that this evidence is
applicable not only to adults, but can establish the identity of the same
person at any stage of his life between babyhood and old age, and for some
time after his death.

       *       *       *       *       *

We read of the dead body of Jezebel being devoured by the dogs of Jezreel,
so that no man might say, "This is Jezebel," and that the dogs left only
her skull, the palms of her hands, and the soles of her feet; but the
palms of the hands and the soles of the feet are the very remains by which
a corpse might be most surely identified, if impressions of them, made
during life, were available.




CHAPTER VIII

PECULIARITIES OF THE DIGITS


The data used in this chapter are the prints of 5000 different digits,
namely, the ten digits of 500 different persons; each digit can thus be
treated, both separately and in combination, in 500 cases. Five hundred
cannot be called a large number, but it suffices for approximate results;
the percentages that it yields may, for instance, be expected to be
trustworthy, more often than not, within two units.

When preparing the tables for this chapter, I gave a more liberal
interpretation to the word "Arch" than subsequently. At first, every
pattern between a Forked-Arch and a Nascent-Loop (Plate 7) was rated as an
Arch; afterwards they were rated as Loops.

The relative frequency of the three several classes in the 5000 digits was
as follows:--

  Arches                     6·5 per cent.
  Loops                     67·5    "
  Whorls                    26·0    "
                           ------
               Total       100·0

From this it appears, that on the average out of every 15 or 16 digits,
one has an arch; out of every 3 digits, two have loops; out of every 4
digits, one has a whorl.

This coarse statistical treatment leaves an inadequate impression, each
digit and each hand having its own peculiarity, as we shall see in the
following table:--

TABLE I.

_Percentage frequency of Arches, Loops, and Whorls on the different
digits, from observations of the 5000 digits of 500 persons._

  +-----------------------------------------------------------------+
  |           |      RIGHT HAND.        ||        LEFT HAND.        |
  |  Digit.   |-----------------------------------------------------|
  |           |Arch.|Loop.|Whorl.|Total.||Arch.|Loop.| Whorl.|Total.|
  |-----------+-----------------------------------------------------|
  |Thumb      |  3  | 53  |  44  | 100  ||  5  | 65  |  30   | 100  |
  |Fore-finger| 17  | 53  |  30  | 100  || 17  | 55  |  28   | 100  |
  |Middle do. |  7  | 78  |  15  | 100  ||  8  | 76  |  16   | 100  |
  |Ring   do. |  2  | 53  |  45  | 100  ||  3  | 66  |  31   | 100  |
  |Little do. |  1  | 86  |  13  | 100  ||  2  | 90  |   8   | 100  |
  |-----------+-----+-----+------+------||-----+-----+-------+------|
  |   Total   | 30  |323  | 147  | 500  || 35  |352  | 113   | 500  |
  +-----------------------------------------------------------------+

The percentage of arches on the various digits varies from 1 to 17; of
loops, from 53 to 90; of whorls, from 13 to 45, consequently the
statistics of the digits must be separated, and not massed
indiscriminately.

Are the A. L. W. patterns distributed in the same way upon the
corresponding digits of the two hands? The answer from the last table is
distinct and curious, and will be best appreciated on rearranging the
entries as follows:--

TABLE II.

  +-----------------------------------------------------------------+
  |            |     ARCHES.    ||     LOOPS.     ||     WHORLS.    |
  |   Digit.   |----------------||----------------||----------------|
  |            | Right. | Left. || Right. | Left. || Right. | Left. |
  |------------|--------|-------||--------|-------||----------------|
  | Fore-finger|   17   |   17  ||   53   |   53  ||   30   |   28  |
  | Middle do. |    7   |    8  ||   78   |   76  ||   15   |   16  |
  | Little do. |    1   |    2  ||   86   |   90  ||   13   |    8  |
  |            |        |       ||        |       ||        |       |
  | Thumb      |    3   |    5  ||   53   |   65  ||   44   |   30  |
  | Ring   do. |    2   |    3  ||   53   |   66  ||   45   |   31  |
  |------------|--------|-------||--------|-------||----------------|
  | Total 1000 |   30   |   35  ||  323   |  350  ||  147   |  113  |
  +-----------------------------------------------------------------+

The digits are seen to fall into two well-marked groups; the one including
the fore, middle, and little fingers, the other including the thumb and
ring-finger. As regards the first group, the frequency with which any
pattern occurs in any named digit is statistically the same, whether that
digit be on the right or on the left hand; as regards the second group,
the frequency differs greatly in the two hands. But though in the first
group the two fore-fingers, the two middle, and the two little fingers of
the right hand are severally circumstanced alike in the frequency with
which their various patterns occur, the difference between the frequency
of the patterns on a fore, a middle, and a little finger, respectively, is
very great.

In the second group, though the thumbs on opposite hands do not resemble
each other in the statistical frequency of the A. L. W. patterns, nor do
the ring-fingers, there is a great resemblance between the respective
frequencies in the thumbs and ring-fingers; for instance, the Whorls on
either of these fingers on the left hand are only two-thirds as common as
those on the right. The figures in each line and in each column are
consistent throughout in expressing these curious differences, which must
therefore be accepted as facts, and not as statistical accidents, whatever
may be their explanation.

One of the most noticeable peculiarities in Table I. is the much greater
frequency of Arches on the fore-fingers than on any other of the four
digits. It amounts to 17 per cent on the fore-fingers, while on the thumbs
and on the remaining fingers the frequency diminishes (Table III.) in a
ratio that roughly accords with the distance of each digit from the
fore-finger.

TABLE III.

  +--------------------------------------------+
  |      _Percentage frequency of Arches._     |
  |--------------------------------------------|
  |Hand.|Thumb.| Fore- |Middle | Ring- |Little |
  |     |      |finger.|finger.|finger.|finger.|
  |-----|------|-------|-------|-------|-------|
  |Right|  3   |  17   |   7   |   2   |   1   |
  |Left |  5   |  17   |   8   |   3   |   4   |
  |-----|------|-------|-------|-------|-------|
  |Mean |  4   |  17   |  7·5  |  2·5  |  2·5  |
  +--------------------------------------------+

The frequency of Loops (Table IV.) has two maxima; the principal one is on
the little finger, the secondary on the middle finger.

TABLE IV.

  +--------------------------------------------+
  |       _Percentage frequency of Loops._     |
  |--------------------------------------------|
  |Hand.|Thumb.|Fore-  |Middle |Ring-  |Little |
  |     |      |finger.|finger.|finger.|finger.|
  |-----|------|-------|-------|-------|-------|
  |Right|  53  |   53  |   78  |   66  |   86  |
  |Left |  65  |   55  |   76  |   53  |   90  |
  |-----|------|-------|-------|-------|-------|
  |Mean |  59  |   54  |   77  |  59·5 |   88  |
  +--------------------------------------------+

Whorls (Table V.) are most common on the thumb and the ring-finger, most
rare on the middle and little fingers.

TABLE V.

  +--------------------------------------------+
  |     _Percentage frequency of Whorls._      |
  |--------------------------------------------|
  |Hand.|Thumb.|Fore-  |Middle |Ring-  |Little |
  |     |      |finger.|finger.|finger.|finger.|
  |-----|------|-------|-------|-------|-------|
  |Right|  44  |   30  |   15  |  45   |  13   |
  |Left |  30  |   28  |   16  |  31   |   8   |
  |-----|------|-------|-------|-------|-------|
  |Mean |  37  |   29  |  15·5 |  38   | 10·5  |
  +--------------------------------------------+

The fore-finger is peculiar in the frequency with which the direction of
the slopes of its loops differs from that which is by far the most common
in all other digits. A loop _must_ have a slope, being caused by the
disposition of the ridges into the form of a pocket, opening downwards to
one or other side of the finger. If it opens towards the inner or thumb
side of the hand, it will be called an inner slope; if towards the outer
or little-finger side, it will be called an outer slope. In all digits,
except the fore-fingers, the inner slope is much the more rare of the two;
but in the fore-fingers the inner slope appears two-thirds as frequently
as the outer slope. Out of the percentage of 53 loops of the one or other
kind on the right fore-finger, 21 of them have an inner and 32 an outer
slope; out of the percentage of 55 loops on the left fore-finger, 21 have
inner and 34 have outer slopes. These subdivisions 21-21 and 32-34
corroborate the strong statistical similarity that was observed to exist
between the frequency of the several patterns on the right and left
fore-fingers; a condition which was also found to characterise the middle
and little fingers.

It is strange that Purkenje considers the "inner" slope on the fore-finger
to be more frequent than the "outer" (p. 86, ~4~). My nomenclature differs
from his, but there is no doubt as to the disagreement in meaning. The
facts to be adduced hereafter make it most improbable that the persons
observed were racially unlike in this particular.

The tendencies of digits to resemble one another will now be considered in
their various combinations. They will be taken two at a time, in order to
learn the frequency with which both members of the various couplets are
affected by the same A. L. W. class of pattern. Every combination will be
discussed, except those into which the little finger enters. These are
omitted, because the overwhelming frequency of loops in the little fingers
would make the results of comparatively little interest, while their
insertion would greatly increase the size of the table.

TABLE VI_a_.

_Percentage of cases in which the same class of pattern occurs in the_
same digits _of the two hands_.

(From observation of 5000 digits of 500 persons.)

  +----------------------------------------------------+
  | Couplets of Digits.  |Arches.|Loops.|Whorls.|Total.|
  |----------------------|-------|------|-------|------|
  |The two thumbs        |   2   |  48  |  24   |  74  |
  |   "    fore-fingers  |   9   |  38  |  20   |  67  |
  |   "    middle fingers|   3   |  65  |   9   |  77  |
  |   "    ring-fingers  |   2   |  46  |  26   |  74  |
  |----------------------------------------------------|
  |        Mean of the Totals                      72  |
  +----------------------------------------------------+

TABLE VI_b_.

_Percentage of cases in which the same class of pattern occurs in various
couplets of_ different digits.

(From 500 persons as above.)

  +-----------------------------------------------------------------------+
  |  Couplets of |      OF SAME HANDS.       ||    OF OPPOSITE HANDS.     |
  |   Digits.    |---------------------------||---------------------------|
  |              |Arch.|Loops.|Whorls.|Total.||Arch.|Loops.|Whorls.|Total.|
  |--------------|-----|------|-------|------||-----|------|-------|------|
  |Thumb and     |     |      |       |      ||     |      |       |      |
  | fore-finger  |  2  |  35  |  16   |  53  ||  2  |  33  |  15   | 50   |
  |Thumb and     |     |      |       |      ||     |      |       |      |
  | middle finger|  1  |  48  |   9   |  58  ||  1  |  47  |   8   | 56   |
  |Thumb and     |     |      |       |      ||     |      |       |      |
  | ring-finger  |  1  |  40  |  20   |  61  ||  1  |  38  |  18   | 57   |
  |Fore and      |     |      |       |      ||     |      |       |      |
  | middle finger|  5  |  48  |  12   |  65  ||  5  |  46  |  11   | 62   |
  |Fore and      |     |      |       |      ||     |      |       |      |
  | ring-finger  |  2  |  35  |  17   |  54  ||  2  |  35  |  17   | 54   |
  |Middle and    |     |      |       |      ||     |      |       |      |
  | ring-finger  |  2  |  50  |  13   |  65  ||  2  |  50  |  12   | 64   |
  |-----------------------------------------------------------------------|
  |          Means of the Totals         59  ||                      57   |
  +-----------------------------------------------------------------------+

A striking feature in this last table is the close similarity between
corresponding entries relating to the same and to the opposite hands.
There are eighteen sets to be compared; namely, six couplets of different
names, in each of which the frequency of three different classes of
patterns is discussed. The eighteen pairs of corresponding couplets are
closely alike in every instance. It is worth while to rearrange the
figures as below, for the greater convenience of observing their
resemblances.

TABLE VII.

  +---------------------------------------------------------------+
  |                |  Arches in   ||   Loops in   ||  Whorls in   |
  |                |--------------||--------------||--------------|
  |   Couplet.     |Same |Opposite||Same |Opposite||Same |Opposite|
  |                |hand.| hand.  ||hand.| hand.  ||hand.| hand.  |
  |----------------|-----|--------||-----|--------||-----|--------|
  |Thumb and       |     |        ||     |        ||     |        |
  |  fore-finger   |  2  |   2    || 35  |   33   ||  16 |   15   |
  |Thumb and       |     |        ||     |        ||     |        |
  |  middle finger |  1  |   1    || 48  |   47   ||   9 |    8   |
  |Thumb and ring- |     |        ||     |        ||     |        |
  |  finger        |  1  |   1    || 40  |   38   ||  20 |   18   |
  |Fore and middle |     |        ||     |        ||     |        |
  |  finger        |  5  |   5    || 48  |   46   ||  12 |   11   |
  |Fore and ring-  |     |        ||     |        ||     |        |
  |  finger        |  2  |   2    || 35  |   35   ||  17 |   17   |
  |Middle and ring-|     |        ||     |        ||     |        |
  |  finger        |  2  |   2    || 50  |   50   ||  13 |   12   |
  +---------------------------------------------------------------+

The agreement in the above entries is so curiously close as to have
excited grave suspicion that it was due to some absurd blunder, by which
the same figures were made inadvertently to do duty twice over, but
subsequent checking disclosed no error. Though the unanimity of the
results is wonderful, they are fairly arrived at, and leave no doubt that
the relationship of any one particular digit, whether thumb, fore, middle,
ring or little finger, to any other particular digit, is the same, whether
the two digits are on the same or on opposite hands. It would be a most
interesting subject of statistical inquiry to ascertain whether the
distribution of malformations, or of the various forms of skin disease
among the digits, corroborates this unexpected and remarkable result. I am
sorry to have no means of undertaking it, being assured on good authority
that no adequate collection of the necessary data has yet been published.

It might be hastily inferred from the statistical identity of the
connection between, say, the right thumb and each of the two fore-fingers,
that the patterns on the two fore-fingers ought always to be alike,
whether arch, loop, or whorl. If X, it may be said, is identical both with
Y and with Z, then Y and Z must be identical with one another. But the
statement of the problem is wrong; X is not identical with Y and Z, but
only bears an identical amount of statistical resemblance to each of them;
so this reasoning is inadmissible. The character of the pattern on any
digit is determined by causes of whose precise nature we are ignorant; but
we may rest assured that they are numerous and variable, and that their
variations are in large part independent of one another. We can in
imagination divide them into groups, calling those that are common to the
thumb and the fore-finger of either hand, and to those couplets
exclusively, the A causes; those that are common to the two thumbs and to
these exclusively, the B causes; and similarly those common to the two
fore-fingers exclusively, the C causes.

Then the sum of the variable causes determining the class of pattern in
the four several digits now in question are these:--

  Right thumb        A + B + an unclassed residue called X(=1=)
  Left thumb         A + B +        "        "      "    X(=2=)
  Right fore-finger  A + C +        "        "      "    Z(=1=)
  Left fore-finger   A + C +        "        "      "    Z(=2=)

The nearness of relationship between the two thumbs is sufficiently
indicated by a fraction that expresses the proportion between all the
causes common to the two thumbs exclusively, and the totality of the
causes by which the A. L. W. class of the patterns of the thumbs is
determined, that is to say, by

            A + B
  -----------------------      (1).
  A + B + X(=1=) + X(=2=)

Similarly, the nearness of the relationship between the two fore-fingers
by

            A + C
  -----------------------      (2).
  A + C + Z(=1=) + Z(=2=)

And that between a thumb and a fore-finger by

                        A
  ---------------------------------------------------      (3).
  A + B + C + X(=1=) (or X(=2=)) + Z(=1=) (or Z(=2=))

The fractions (1) and (2) being both greater than (3), it follows that the
relationships between the two thumbs, or between the two fore-fingers, are
closer than that between the thumb and either fore-finger; at the same
time it is clear that neither of the two former relationships is so close
as to reach identity. Similarly as regards the other couplets of digits.
The tabular entries fully confirm this deduction, for, without going now
into further details, it will be seen from the "Mean of the Totals" at the
bottom line of Table VI_b_ that the average percentage of cases in which
two different digits have the same class of patterns, whether they be on
the same or on opposite hands, is 59 or 57 (say 58), while the average
percentage of cases in which right and left digits bearing the same name
have the same class of pattern (Table VI_a_) is 72. This is barely
two-thirds of the 100 which would imply identity. At the same time, the 72
considerably exceeds the 58.

Let us now endeavour to measure the relationships between the various
couplets of digits on a well-defined centesimal scale, first recalling the
fundamental principles of the connection that subsists between
relationships of all kinds, whether between digits, or between kinsmen, or
between any of those numerous varieties of related events with which
statisticians deal.

Relationships are all due to the joint action of two groups of variable
causes, the one common to both of the related objects, the other special
to each, as in the case just discussed. Using an analogous nomenclature to
that already employed, the peculiarity of one of the two objects is due to
an aggregate of variable causes that we may call C+X, and that of the
other to C+Z, in which C are the causes common to both, and X and Z the
special ones. In exact proportion as X and Z diminish, and C becomes of
overpowering effect, so does the closeness of the relationship increase.
When X and Z both disappear, the result is identity of character. On the
other hand, when C disappears, all relationship ceases, and the variations
of the two objects are strictly independent. The simplest case is that in
which X and Z are equal, and _in this_, it becomes easy to devise a scale
in which 0° shall stand for no relationship, and 100° for identity, and
upon which the intermediate degrees of relationship may be marked at their
proper value. Upon this assumption, but with some misgiving, I will
attempt to subject the digits to this form of measurement. It will save
time first to work out an example, and then, after gaining in that way, a
clearer understanding of what the process is, to discuss its defects. Let
us select for our example the case that brings out these defects in the
most conspicuous manner, as follows:--

Table V. tells us that the percentage of whorls in the right ring-finger
is 45, and in the left ring-finger 31. Table VI_a_ tells us that the
percentage of the double event of a whorl occurring on both the
ring-fingers of the same person is 26. It is required to express the
relationship between the right and left ring-fingers on a centesimal
scale, in which 0° shall stand for no relationship at all, and 100° for
the closest possible relationship.

If no relationship should exist, there would nevertheless be a certain
percentage of instances, due to pure chance, of the double event of whorls
occurring in both ring-fingers, and it is easy to calculate their
frequency from the above data. The number of possible combinations of 100
right ring-fingers with 100 left ones is 100 × 100, and of these 45 × 31
would be double events as above (call these for brevity "double whorls").
Consequently the chance of a double whorl in any single couplet is
(45×31)/(100×100), and their average frequency in 100 couplets,--in other
words, their average percentage is (45×31)/100 = 13·95, say 14. If, then,
the observed percentage of double whorls should be only 14, it would be a
proof that the A. L. W. classes of patterns on the right and left
ring-fingers were quite independent; so their relationship, as expressed
on the centesimal scale, would be 0°. There could never be less than 14
double whorls under the given conditions, except through some statistical
irregularity.

Now consider the opposite extreme of the closest possible relationship,
subject however, and this is the weak point, to the paramount condition
that the average frequencies of the A. L. W. classes may be taken as
_pre-established_. As there are 45 per cent of whorls on the right
ring-finger, and only 31 on the left, the tendency to form double whorls,
however stringent it may be, can only be satisfied in 31 cases. There
remains a superfluity of 14 per cent cases in the right ring-finger which
perforce must have for their partners either arches or loops. Hence the
percentage of frequency that indicates the closest feasible relationship
under the pre-established conditions, would be 31.

The range of all possible relationships in respect to whorls, would
consequently lie between a percentage frequency of the minimum 14 and the
maximum 31, while the observed frequency is of the intermediate value of
26. Subtracting the 14 from these three values, we have the series of 0,
12, 17. These terms can be converted into their equivalents in a
centesimal scale that reaches from 0° to 100° instead of from 0° to 17°,
by the ordinary rule of three, 12:_x_::17:100; _x_=70 or 71, whence the
value _x_ of the observed relationship on the centesimal scale would be
70° or 71°, neglecting decimals.

This method of obtaining the value of 100° is open to grave objection in
the present example. We have no right to consider that the 45 per cent of
whorls on the right ring-finger, and the 31 on the left, can be due to
pre-established conditions, which would exercise a paramount effect even
though the whorls were due entirely to causes common to both fingers.
There is some self-contradiction in such a supposition. Neither are we at
liberty to assume that the respective effects of the special causes X and
Z are equal in average amount; if they were, the percentage of whorls on
the right and on the left finger would invariably be equal.

In this particular example the difficulty of determining correctly the
scale value of 100° is exceptionally great; elsewhere, the percentages of
frequency in the two members of each couplet are more alike. In the two
fore-fingers, and again in the two middle fingers, they are closely alike.
Therefore, in these latter cases, it is not unreasonable to pass over the
objection that X and Z have not been proved to be equal, but we must
accept the results in all other cases with great caution.

When the digits are of different names,--as the thumb and the
fore-finger,--whether the digits be on the same or on opposite hands,
there are two cases to be worked out; namely, such as (1) right thumb and
left fore-finger, and (2) left thumb and right fore-finger. Each accounts
for 50 per cent of the observed cases; therefore the mean of the two
percentages is the correct percentage. The relationships calculated in the
following table do not include arches, except in two instances mentioned
in a subsequent paragraph, as the arches are elsewhere too rare to furnish
useful results.

It did not seem necessary to repeat the calculation for couplets of digits
of different names, situated on opposite hands, as those that were
calculated on closely the same data for similar couplets situated on the
same hands, suffice for both. It is evident from the irregularity in the
run of the figures that the units in the several entries cannot be more
than vaguely approximate. They have, however, been retained, as being
possibly better than nothing at all.

TABLE VIII.

_Approximate Measures of Relationship between the various Digits, on a
Centesimal Scale._

(0° = no relationship; 100° = the utmost feasible likeness.)

  +------------------------------------------------------------+
  |            Couplets.            | Loops. | Whorls.| Means. |
  |---------------------------------|--------|--------|--------|
  | _Digits of the same name._      |        |        |        |
  |                                 |        |        |        |
  | Right and left thumbs           |   57   |   64   |   61   |
  |   "        "   fore-fingers     |   37   |   59   |   48   |
  |   "        "   middle fingers   |   34   |   52   |   43   |
  |   "        "   ring fingers     |   61   |   70   |   65   |
  |---------------------------------|--------|--------|--------|
  |                  Means          |   47°  |   61°  |   54°  |
  |---------------------------------|--------|--------|--------|
  | _Digits of different names on   |        |        |        |
  | the same or on opposite hands._ |        |        |        |
  |                                 |        |        |        |
  | Thumb and fore-finger           |   19   |   29   |   24   |
  |     "     middle finger         |   19   |   34   |   27   |
  |     "     ring-finger           |   33   |   44   |   39   |
  | Fore and middle finger          |   52   |   68   |   60   |
  |     "    ring finger            |   13   |   34   |   23   |
  | Middle and ring finger          |   31   |   74   |   52   |
  |---------------------------------|--------|--------|--------|
  |                  Means          |   28°  |   47°  |   37°  |
  +------------------------------------------------------------+

The arches were sufficiently numerous in the fore-fingers (17 per cent) to
fully justify the application of this method of calculation. The result
was 43°, which agrees fairly with 48°, the mean of the loops and the
whorls. In the middle finger the frequency of the arches was only half the
above amount and barely suffices for calculation. It gave the result of
38°, which also agrees fairly with 43°, the mean of the loops and the
whorls for that finger.

Some definite results may be gathered from this table notwithstanding the
irregularity with which the figures run. Its upper and lower halves
clearly belong to different statistical groups, the entries in the former
being almost uniformly larger than those in the latter, in the proportion
of 54° to 37°, say 3 to 2, which roughly represents in numerical terms the
nearer relationship between digits of the same name, as compared to that
between digits of different names. It seems also that of the 6 couplets of
digits bearing different names, the relationship is closest between the
middle finger and the two adjacent ones (60° and 52°, as against 24°, 27°,
39° and 23°). It is further seen in every pair of entries that whorls are
related together more closely than loops. I note this, but cannot explain
it. So far as my statistical inquiries into heredity have hitherto gone,
all peculiarities were found to follow the same law of transmission, none
being more surely inherited than others. If there were a tendency in any
one out of many alternative characters to be more heritable than the rest,
that character would become universally prevalent, in the absence of
restraining influences. But it does not follow that there are no peculiar
restraining influences here, nor that what is true for heredity, should be
true, in all its details, as regards the relationships between the
different digits.




CHAPTER IX

METHODS OF INDEXING


In this chapter the system of classification by Arches, Loops, and Whorls
described in Chapter V. will be used for indexing two, three, six or ten
digits, as the case may be.

An index to each set of finger marks made by the same person, is needful
in almost every kind of inquiry, whether it be for descriptive purposes,
for investigations into race and heredity, or into questions of symmetry
and correlation. It is essential to possess an index to the finger marks
of known criminals before the method of finger prints can be utilised as
an organised means of detection.

The ideal index might be conceived to consist of a considerable number of
compartments, or their equivalents, each bearing a different
index-heading, into which the sets of finger prints of different persons
may be severally sorted, so that all similar sets shall lie in the same
compartment.

The principle of the proposed method of index-headings is, that they
should depend upon a few conspicuous differences of pattern in many
fingers, and not upon many minute differences in a few fingers. It is
carried into effect by distinguishing the A. L. W. class of pattern on
each digit in succession, by a letter,--_a_ for Arch, _l_ for Loop, _w_
for Whorl; or else, as an alternative method, to subdivide _l_ by using
_i_ for a loop with an Inner slope, and _o_ for one with an Outer slope,
as the case may be. In this way, the class of pattern in each set of ten
digits is described by a sequence of ten letters, the various combinations
of which are alphabetically arranged and form the different
index-headings. Let us now discuss the best method of carrying out this
principle, by collating the results of alternative methods of applying it.
We have to consider the utility of the _i_ and _o_ as compared to the
simple _l_, and the gain through taking all ten digits into account,
instead of only some of them.

It will be instructive to print here an actual index to the finger prints
of 100 different persons, who were not in any way selected, but taken as
they came, and to use it as the basis of a considerable portion of the
following remarks, to be checked where necessary, by results derived from
an index to 500 cases, in which these hundred are included.

This index is compiled on the principle shortly to be explained, entitled
the "_i_ and _o_ fore-finger" method.

TABLE IX.--INDEX TO 100 SETS OF FINGER PRINTS.

  +------------------------------------+
  |      |    A       B      C     D   |
  |Order |  Right.  Left.   Rt.   Lt.  |
  | of   |-----------------------------|
  |Entry.|  F.M.R.  F.M.R.  T.L.  T.L. |
  |------|-----------------------------|
  |   1  | _a a a   a a a   a a   l a_ |
  |   2  | _  "       "     a l   a l_ |
  |   3  | _  "       "      "     " _ |
  |   4  | _  "       "     w l   l l_ |
  |   5  | _a a l   a a l   a l   a l_ |
  |   6  | _  "       "     l l   l l_ |
  |   7  | _  "       "      "     " _ |
  |   8  | _  "     a a w   l l   l l_ |
  |   9  | _  "     a l l   l l   l l_ |
  |  10  | _  "       "     l w   w l_ |
  |  11  | _  "     o l l   l l   l l_ |
  |  12  | _a a w   a a l   l l   l l_ |
  |  13  | _  "     a l l   l l   l l_ |
  |  14  | _a l a   a a a   l a   l a_ |
  |  15  | _  "       "     l a   l w_ |
  |  16  | _  "     o l l   w l   l l_ |
  |  17  | _a l l   a a l   l l   a l_ |
  |  18  | _  "       "     l l   l l_ |
  |  19  | _  "       "      "     " _ |
  |  20  | _  "       "      "     " _ |
  |  21  | _  "       "      "     " _ |
  |  22  | _  "       "      "     " _ |
  |  23  | _  "     a l w   l l   l l_ |
  |  24  | _  "     i l l   l l   l l_ |
  |  25  | _  "       "      "     " _ |
  |  26  | _a l l   i l l   w l   l l_ |
  |  27  | _  "     o a l   w l   l l_ |
  |  28  | _  "     o l l   w l   l l_ |
  |  29  | _  "     w w w   w l   l l_ |
  |  30  | _a l w   i l w   l l   l l_ |
  |  31  | _  "     o a l   l l   l l_ |
  |  32  | _  "     o l l   l w   l l_ |
  |  33  | _  "       "     w l   w l_ |
  |  34  | _  "     o l w   a l   a l_ |
  |  35  | _i l l   a l l   w l   l l_ |
  |  36  | _  "       "     w l   w l_ |
  |  37  | _  "     i l l   l l   l l_ |
  |  38  | _  "       "      "     " _ |
  |  39  | _  "       "      "     " _ |
  |  40  | _  "       "      "     " _ |
  |  41  | _i l l   i l l   w l   l l_ |
  |  42  | _  "     i w w   w l   w l_ |
  |  43  | _i l w   i l l   l l   w l_ |
  |  44  | _  "       "     w w   w l_ |
  |  45  | _  "     i l w   w w   w l_ |
  |  46  | _  "     i w l   l l   l l_ |
  |  47  | _  "     w l w   w l   w l_ |
  |  48  | _  "     w w l   l l   l l_ |
  |  49  | _i w w   a l l   w l   w l_ |
  |  50  | _  "     w w w   w l   w l_ |
  |  51  | _  "       "      "     " _ |
  |  52  | _o a w   o l l   l l   l l_ |
  |  53  | _o l l   o l l   l l   l l_ |
  |  54  | _  "       "      "     " _ |
  |  55  | _  "       "      "     " _ |
  |  56  | _  "       "     w l   w l_ |
  |  57  | _  "     i l l   l l   l l_ |
  |  58  | _  "       "      "     " _ |
  |  59  | _  "       "      "     " _ |
  |  60  | _  "     o l l   l l   l l_ |
  |  61  | _  "       "      "     " _ |
  |  62  | _  "       "      "     " _ |
  |  63  | _  "       "      "     " _ |
  |  64  | _  "       "      "     " _ |
  |  65  | _  "       "      "     " _ |
  |  66  | _  "     w a l   l l   w l_ |
  |  67  | _  "     w w w   l l   w l_ |
  |  68  | _o l w   a l l   l l   l l_ |
  |  69  | _  "       "     w l   w l_ |
  |  70  | _  "     i l l   w l   w l_ |
  |  71  | _  "     o l l   l l   l l_ |
  |  72  | _  "       "      "     " _ |
  |  73  | _  "     o l w   l l   l l_ |
  |  74  | _  "       "      "     " _ |
  |  75  | _w l l   i l l   l l   w l_ |
  |  76  | _  "       "      "     " _ |
  |  77  | _w l l   w l l   l l   l l_ |
  |  78  | _  "       "      "     " _ |
  |  79  | _  "       "     w l   w l_ |
  |  80  | _  "     w l w   l l   l l_ |
  |  81  | _w l w   o l w   l l   l l_ |
  |  82  | _  "       "     l l   a l_ |
  |  83  | _  "       "     w l   l l_ |
  |  84  | _  "     w w w   w l   w l_ |
  |  85  | _  "       "     w w   l l_ |
  |  86  | _  "       "     w w   l w_ |
  |  87  | _  "       "     w w   w w_ |
  |  88  | _  "       "      "     " _ |
  |  89  | _w w l   i l l   l l   l l_ |
  |  90  | _  "     w l l   w l   l l_ |
  |  91  | _w w w   o l w   w l   l l_ |
  |  92  | _  "     w l w   w l   w l_ |
  |  93  | _  "       "      "     " _ |
  |  94  | _  "     w w l   l l   l w_ |
  |  95  | _  "     w w w   i l   l l_ |
  |  96  | _  "       "     w l   l l_ |
  |  97  | _  "       "     w l   w l_ |
  |  98  | _  "       "     w w   w l_ |
  |  99  | _  "       "      "     " _ |
  | 100  | _  "       "     w w   w w_ |
  +------------------------------------+

The sequence in which the digits have been registered is not from the
thumb outwards to the little finger, but, on account of various good
reasons that will be appreciated as we proceed, in the following order.

The ten digits are registered in four groups, which are distinguished in
the Index by the letters A, B, C, D:--

    A. _First._ The fore, middle, and ring-fingers of the _right_ hand
    taken in that order.

    B. _Second._ The fore, middle, and ring-fingers of the _left_ hand
    taken in that order.

    C. _Third._ The thumb and little finger of the _right_ hand.

    D. _Fourth._ The thumb and little finger of the _left_ hand.

Consequently an index-heading will be of the form--

  First         Second      Third      Fourth
  group.        group.      group.     group.

  _a a l_      _a a w_      _l l_      _l l_

These index-headings are catalogued in alphabetical order. The method used
in the Index is that which takes note of no slopes, except those of loops
in the fore-finger of either hand. Consequently the index-heading for my
own digits, printed on the title-page, is _wlw oll wl wl_. Those of the
eight sets in Plate VI. are as follows:--

  _i l w    i l l    w w    w l_
  _o l w    o l w    w l    l l_
  _o l w    o l w    w l    l l_
  _o l w    o l l    l l    l l_
  _i l w    i l w    w l    w l_
  _i l w    i w l    l l    l l_
  _i l l    w w l    l l    l l_
  _o l l    a a l    l l    a l_
  _o a a    a a a    l a    l a_

For convenience of description and reference, the successive entries in
the specimen index have been numbered from 1 to 100, but that is no part
of the system: those figures would be replaced in a real index by names
and addresses.

A preliminary way of obtaining an idea of the differentiating power of an
index is to count the number of the different headings that are required
to classify a specified number of cases. A table is appended which shows
the numbers of the headings in the three alternative methods (1) of noting
slopes of all kinds in all digits, (2) of noting slopes of Loops only and
in the fore-fingers only, and (3) of disregarding the slopes altogether.
Also in each of these three cases taking account of--

    (_a_) All the ten digits;

    (_b_) the fore, middle, and ring-fingers of both hands;

    (_c_) those same three fingers, but of the right hand only;

    (_d_) the fore and middle fingers of the right hand.

TABLE X.

_No. of different index-heads in 100 sets of Finger Prints._

  +---------------------------------------------------------------+
  |           |                    |      Account taken of        |
  |  No. of   |                    |------------------------------|
  |  digits   |    Digits noted.   |   All   |_i_ and _o_|  No    |
  | regarded. |                    | slopes. |  in fore- | slope. |
  |           |                    |         |  fingers. |        |
  |-----------|--------------------|---------|-----------|--------|
  |     10    | All the 10 digits  |    82   |     76    |   71   |
  |           |                    |         |           |        |
  |           | Fore, middle,      |         |           |        |
  |      6    | and ring-fingers   |    65   |     50    |   43   |
  |           | of both hands      |         |           |        |
  |           |                    |         |           |        |
  |      3    | Of right hand only |    25   |     16    |   14   |
  |           |                    |         |           |        |
  |      2    | Fore and middle of |    12   |      8    |    7   |
  |           | right hand only    |         |           |        |
  +---------------------------------------------------------------+

The column headed "all slopes" refers to the method first used with
success, and described in my Memoir, already alluded to (_Proc. Roy.
Soc._, 1891), accompanied by a specimen index, from which the present one
was derived. There the direction of the slope of every pattern that has
one, is taken into account, and in order to give as much scope as
possible to the method, the term Arch (I then called it a Primary) was
construed somewhat over-liberally (see p. 114). It was made to include the
forked-arch Fig. 12 (~2~), and even the nascent-loop (~9~), so long as not
more than a single recurved ridge lay within the outline of the pattern;
therefore many of the so-called arches had slopes. It is not necessary to
trouble the reader with the numerical nomenclature that was then used, the
method itself being now obsolete. Full particulars of it are, however,
given in the Memoir.

A somewhat large experience in sorting finger prints in various ways and
repeatedly, made it only too evident that the mental strain and risk of
error caused by taking all slopes into account was considerable. The
judgment became fatigued and the eye puzzled by having to assign opposite
meanings to the same actual direction of a slope in the right and left
hands respectively. There was also a frequent doubt as to the existence of
a slope in large whorls of the spiral- and circlet-in-loop patterns (Fig.
13, ~21~, ~22~) when the impressions had not been rolled. A third
objection is the rarity of the inner slopes in any other digit than the
fore-finger. It acted like a soporific to the judgment not only of myself
but of others, so that when an inner slope did occur it was apt to be
overlooked. The first idea was to discard slopes altogether,
notwithstanding the accompanying loss of index power, but this would be an
unnecessarily trenchant measure. The slope of a loop, though it be on the
fore-finger alone, decidedly merits recognition, for it differentiates
such loops into two not very unequal classes. Again, there is little
chance of mistake in noting it, the impression of the thumb on the one
side and those of the remaining fingers on the other, affording easy
guidance to the eye and judgment. These considerations determined the
method I now use exclusively, by which Table IX. was compiled, and to
which the second column of Table X., headed "_i_ and _o_ in fore-fingers,"
refers.

The heading of the third column, "no slope," explains itself, no account
having been there taken of any slopes whatever, so _i_ and _o_ disappear,
having become merged under _l_.

The table gives a very favourable impression of the differentiating power
of all these methods of indexing. By the "_i_ and _o_ fore-finger" method,
it requires as many as 76 different index-headings to include the finger
prints of 100 different persons, 195 of 300 persons, and 285 of 500.

The number of entries under each index-heading varies greatly; reference
to the index of 100 sets showing no less than six entries (Nos. 60-65)
under one of them, and four entries (Nos. 18-21 and 37-40) under each of
two others. Thus, although a large portion of the 100 sets are solitary
entries under their several headings, and can be found by a single
reference, the remainder are grouped together like the commoner surnames
in a directory. They are troublesome to distinguish, and cannot be
subdivided at all except by supplementary characteristics, such as the
number of ridges in some specified part of the pattern, or the character
of the cores.

In other respects the difference of merit between the three methods is
somewhat greater, as is succinctly indicated by the next table.

TABLE XI.--_In 100 Sets._

  +-----------------------------------------------------+
  |                    |No. of different index-headings.|
  | Number of Entries  |--------------------------------|
  |under the same head.|   All   |  _i_ and _o_ |  No   |
  |                    | slopes. | fore-fingers | slope.|
  |                    |         |     only.    |       |
  |--------------------|---------|--------------|-------|
  |          1         |    71   |       63     |   58  |
  |          2         |    10   |        8     |    9  |
  |          3         |     1   |        3     |    1  |
  |          4         |   ...   |        2     |    2  |
  |          5         |   ...   |      ...     |  ...  |
  |          6         |     1   |      ...     |  ...  |
  |         13         |   ...   |      ...     |    1  |
  |--------------------|---------|--------------|-------|
  |      Total         |    83   |       76     |   71  |
  +-----------------------------------------------------+

Hence it is evident that the second method of "_i-o_ fore-finger" is
capable of dealing rapidly with 100 cases, but that the method of "no
slope" will give trouble in twelve out of the hundred cases.

TABLE XII.

_Index-headings under which more than 1 per cent of the sets of Finger
Prints were registered._

(500 sets observed.)

  +----------------------------------------------------
  |          _i_ and _o_ in fore-fingers.            ||
  |----------------------------------------------------
  |    No.   |                             |Frequency||
  |    for   |       Index-heading.        |   per   ||
  |Reference.|                             |  cent.  ||
  |----------|-----------------------------|---------||
  |     1    | _a l l   a l l   l l   l l_ |   1·2   ||
  |     2    | _a l l   i l l    "     " _ |   1·6   ||
  |----------|-----------------------------|---------||
  |     3    | _i l l   i l l    "     " _ |   2·8   ||
  |     4    | _o l l   i l l    "     " _ |   1·4   ||
  |     5    | _o l l   o l l    "     " _ |   4·0   ||
  |----------|-----------------------------|---------||
  |     6    | _i l l   o l l   w l   l l_ |   1·2   ||
  |     7    | _o l l   o l l    "     " _ |   1·4   ||
  |----------|-----------------------------|---------||
  |     8    | _o l l   a l l   l l   l l_ |   2·2   ||
  |     9    | _o l w   u l l    "     " _ |   2·0   ||
  |    10    | _w l l   w l l    "     " _ |   1·2   ||
  |    11    | _w w w   w w w   w w   w w_ |   1·4   ||
  +----------------------------------------------------

  --------------------------------------------------+
                     No slope.                      |
  --------------------------------------------------|
     No.    |                             |Frequency|
     for    |       Index-heading.        |   per   |
  Reference.|                             |  cent.  |
  ----------|-----------------------------|---------|
       I.   | _a l l   a l l   l l   l l_ |   1·2   |
      II.   | _a l l   l l l    "     " _ |   2·2   |
  ----------|-----------------------------|---------|
            |                             |         |
     III.   | _l l l   l l l    "     " _ |   9·2   |
            |                             |         |
  ----------|-----------------------------|---------|
      IV.   | _l l l   l l l   w l   l l_ |   3·2   |
            |                             |         |
  ----------|-----------------------------|---------|
       V.   | _l l l   a l l   l l   l l_ |   3·0   |
      VI.   | _l l w   l l l    "     " _ |   3·0   |
     VII.   | _w l l   w l l    "     " _ |   1·2   |
    VIII.   | _w w w   w w w   w w   w w_ |   1·4   |
  --------------------------------------------------+

    The headings in the right half of the table include more cases than
    the left half, because a combination of two or more cases that
    severally contain less than 1 per cent of the finger prints, and are
    therefore ignored in the first half of the table, may exceed 1 per
    cent and find a place in the second half.

The entries in Table XII. are derived from a catalogue of 500 sets, and
include all entries that appeared more than five times; in other words,
whose frequency exceeded 1 per cent. These are the index-headings that
give enough trouble to deserve notice in catalogues of, say, from 500 to
1000 sets.

In the left half of Table XII. all the index-headings are given, under
each of which more than 1 per cent of the sets fell, when the method of
"_i_ and _o_ in fore-fingers" was adopted; also the respective percentage
of the cases that fell under them. In the right half of the table are the
corresponding index-headings, together with the percentages of frequency,
when the "no slope" method is employed. These are distinguished by Roman
numerals. The great advantage of the "_i_ and _o_ fore-finger" method lies
in its power of breaking up certain large groups which are very
troublesome to deal with by the "no slope" method. According to the latter
as many as 9·2 per cent of all the entries fall under the index-heading
marked III., but according to the "_i-o_ fore-finger" method these are
distributed among the headings 3, 4, and 5. The "all slopes" method has
the peculiar merit of breaking up the large group Nos. 11 and VIII. of
"all whorls," but its importance is not great on that account, as whorls
are distinguishable by their cores, which are less troublesome to observe
than their slopes.

The percentage of all the entries that fall under a single index-heading,
according to the "_i-o_ fore-finger" method, diminishes with the number of
entries at the following rate:--

TABLE XIII.

  +----------------------------------------------------------+
  |                               | Total number of entries. |
  |                               |--------------------------|
  |                               |   100  |   300  |   500  |
  |-------------------------------|--------|--------|--------|
  | Percentage of entries falling |        |        |        |
  |   under a single head         |    63  |  49·0  |  39·8  |
  +----------------------------------------------------------+

It may be that every one of the 4{2} × 3{8}, or one hundred and five
thousand possible varieties of index-headings, according to the "_i-o_
fore-finger" method, may occur in Nature, but there is much probability
that some of them may be so rare that instances of no entry under certain
heads would appear in the register, even of an enormous number of persons.

       *       *       *       *       *

Hitherto we have supposed that prints of the ten fingers have in each case
been indexed. The question now to be considered is the gain through
dealing in each case with all ten digits, instead of following the easier
practice of regarding only a few of them. The following table, drawn up
from the hundred cases by the "all slopes" method, will show its amount.

TABLE XIV.--_From 100 Sets._

  +----------------------------------------------------------------------+
  |                       |         |  No. of different index-headings.  |
  |        Digits.        | No. of  |------------------------------------|
  |                       | digits. |  All    |  _i_ and _o_ | No slope. |
  |                       |         | slopes. | fore-finger. |           |
  |-----------------------|---------|---------|--------------|-----------|
  | Fore and middle of    |         |         |              |           |
  |   right hand          |    2    |    11   |       8      |     7     |
  |                       |         |         |              |           |
  | Fore, middle and ring |         |         |              |           |
  |   of right hand       |    3    |    23   |      16      |    14     |
  |                       |         |         |              |           |
  | Fore, middle and ring |         |         |              |           |
  |   of both hands       |    6    |    65   |      50      |    45     |
  |                       |         |         |              |           |
  | All ten digits        |   10    |    83   |      76      |    73     |
  +----------------------------------------------------------------------+

The trouble of printing, reading off, and indexing the ten digits, is
practically twice that of dealing with the six fingers; namely, three on
each of the hands; the thumb being inconvenient to print from, and having
to be printed separately, even for a dabbed impression, while the fingers
of either hand can be dabbed down simultaneously.

For a large collection the ten digit method is certainly the best, as it
breaks up the big battalions; also in case of one or more fingers having
been injured, it gives reserve material to work upon.

       *       *       *       *       *

We now come to the great difficulty in all classifications; that of
transitional cases. What is to be done with those prints which cannot be
certainly classed as Arches, Loops, or Whorls, but which lie between some
two of them? These occur about once in every forty digits, or once in
every four pairs of hands. The roughest way is to put a mark by the side
of the entry to indicate doubt, a better one is to make a mark that shall
express the nature of the peculiarity; thus a particular eyed pattern
(Plate 10, Fig. 16, _n_) may be transitional between a loop and a whorl;
under whichever of the two it is entered, the mark might be an _e_ to show
that anyhow it is an eye. Then, when it is required to discover whether an
index contains a duplicate of a given specimen in which a transitional
pattern occurs, the two headings between which the doubt lies have to be
searched, and the marked entries will limit the search. Many alternative
ways of marking may be successfully used, but I am not yet prepared to
propose one as being distinctly the best. When there are two of these
marks in the same set, it seldom happens that more than two references
have to be made, as it is usual for the ambiguity to be of the same kind
in both of the doubtful fingers. If the ambiguities were quite
independent, then two marks would require four references, and three marks
would require nine. There are a few nondescript prints that would fall
under a separate heading, such as Z. Similarly, as regards lost or injured
fingers.

I have tried various methods of sub-classification, and find no difficulty
in any of them, but general rules seem inadvisable; it being best to treat
each large group on its own merits.

One method that I have adopted and described in the _Proc. Royal Soc._, is
to sketch in a cursive and symbolic form the patterns of the several
fingers in the order in which they appear in the print, confining myself
to a limited number of symbols, such as might be used for printer's types.
They sufficed fairly for some thousands of the finger marks upon which
they were tried, but doubtless they could be improved. A little violence
has of course to be used now and then, in fitting some unusual patterns to
some one or other of these few symbols. But we are familiar with such
processes in ordinary spelling, making the same letter do duty for
different sounds, as _a_ in the words _as_, _ale_, _ask_, and _all_. The
plan of using symbols has many secondary merits. It facilitates a
leisurely revision of first determinations, it affords a pictorial record
of the final judgment that is directly comparable with the print itself,
and it almost wholly checks blunders between inner and outer slopes. A
beginner in finger reading will educate his judgment by habitually using
them at first.


[Illustration: PLATE 2.

FIG. 3. Form of card used for impressions of the ten digits. 11-1/2 × 5
inches.

FIG. 4. Roller and its bearings, of a pocket printing apparatus.]


The cores give great assistance in breaking up the very large groups of
all-loops (see Table XII., Nos. 11 and VIII.); so does an entry of the
approximate number of ridges in some selected fingers, that lie between
the core and the upper outline of the loop.

       *       *       *       *       *

The plan I am now using for keeping finger prints in regular order, is
this:--In the principal collection, the prints of each person's ten digits
are taken on the same large card; the four fingers of either hand being
_dabbed_ down simultaneously above, and all the ten digits _rolled_
separately below. (Plate 2, Fig. 3.) Each card has a hole three-eighths of
an inch in diameter, punched in the middle near to the bottom edge, and
the cards are kept in trays, which they loosely fit, like the card
catalogues used in many libraries. Each tray holds easily 500 cards, which
are secured by a long stout wire passing like a skewer through the ends of
the box and the holes in the cards. The hinder end of the box is sloped,
so the cards can be tilted back and easily examined; they can be inserted
or removed after withdrawing the wire.

It will be recollected that the leading and therefore the most conspicuous
headings in the index refer to the fore, middle, and ring-fingers of the
right hand, as entered in column A of the Specimen Register (Table IX.)
The variety of these in the "_i_ and _o_ fore-finger" method, of which we
are now speaking, cannot exceed thirty-six, there being only four
varieties (_a_, _i_, _o_, _w_) in the fore-finger, and three varieties
(_a_, _l_, _w_) in each of the other two; so their maximum number is 4 × 3
× 3 = 36. The actual number of such index-headings in 500 cases, and the
number of entries that fell under each, was found to be as follows:--

TABLE XV.

_No. of entries in 500 cases, under each of the thirty-six possible
index-letters for the fore, middle, and ring-fingers of the right hand by
the "i-o fore-finger" method._

  +--------------------------------------------------------------+
  | _a a a_ |  4 || _i a a_ |  1 || _o a a_ |  1 || _w a a_ | -- |
  |     _l_ | 17 ||     _l_ |  3 ||     _l_ |  2 ||     _l_ | -- |
  |     _w_ |  5 ||     _w_ | -- ||     _w_ |  1 ||     _w_ |  1 |
  |         |    ||         |    ||         |    ||         |    |
  | _a l a_ |  3 || _i l a_ | -- || _o l a_ |  2 || _w l a_ |  1 |
  |     _l_ | 45 ||     _l_ | 54 ||     _l_ | 88 ||     _l_ | 40 |
  |     _w_ | 11 ||     _w_ | 33 ||     _w_ | 59 ||     _w_ | 52 |
  |         |    ||         |    ||         |    ||         |    |
  | _a w a_ | -- || _i w a_ | -- || _o w a_ | -- || _w w a_ | -- |
  |     _l_ | -- ||     _l_ |  3 ||     _l_ | -- ||     _l_ | 10 |
  |     _w_ | -- ||     _w_ | 11 ||     _w_ |  6 ||     _w_ | 47 |
  +--------------------------------------------------------------+

    _a_ = Arch.

    _i_ = Inward-sloped Loop on the fore-finger.

    _o_ = Outward-sloped Loop on the fore-finger.

    _l_ = Loop of either kind on the middle or ring finger.

    _w_ = Whorl.

These 500 cases supply no entries at all to eleven of the thirty-six
index-headings, less than five entries (or under 1 per cent) to ten
others, and the supply is distributed very unevenly among the remaining
fifteen. This table makes it easy to calculate beforehand the spaces
required for an index of any specified number of prints, whether they be
on the pages of a Register, or in compartments, or in drawers of movable
cards.




CHAPTER X

PERSONAL IDENTIFICATION


We shall speak in this chapter of the aid that finger prints can give to
personal identification, supposing throughout that facilities exist for
taking them well and cheaply, and that more or less practice in reading
them has been acquired by many persons. A few introductory words will show
this supposition to be reasonable. At the present moment any printer, and
there are many printers in every town, would, at a small charge, blacken a
slab and take the prints effectively, after being warned to use very
little ink, as described in Chapter III. The occupation of finger printing
would, however, fall more naturally into the hands of photographers, who,
in addition to being found everywhere, are peculiarly well suited to it,
for, taken as a class, they are naturally gifted with manual dexterity and
mechanical ingenuity. Having secured good impressions, they could multiply
them when necessary, and enlarge when desired, while the ticketing and
preservation of the negatives would fall into their usual business
routine. As they already occupy themselves with one means of
identification, a second means of obtaining the same result is allied to
their present work.

Were it the custom for persons about to travel to ask for prints of their
fingers when they were photographed, a familiarity with the peculiarities
of finger prints, and the methods of describing and classifying them,
would become common. Wherever finger prints may be wanted for purposes of
attestation and the like, the fact mentioned by Sir W. Herschel (p. 45) as
to the readiness with which his native orderlies learnt to take them with
the ink of his office stamp, must not be forgotten.

The remarks about to be made refer to identification generally, and are
not affected by the fact that the complete process may or may not include
the preliminary search of a catalogue; the two stages of search and of
comparison will be treated separately towards the close of the chapter.

In civilised lands, honest citizens rarely need additional means of
identification to their signatures, their photographs, and to personal
introductions. The cases in which other evidence is wanted are chiefly
connected with violent death through accident, murder, or suicide, which
yield the constant and gruesome supply to the Morgue of Paris, and to
corresponding institutions in other large towns, where the bodies of
unknown persons are exposed for identification, often in vain. But when
honest persons travel to distant countries where they have few or no
friends, the need for a means of recognition is more frequently felt. The
risk of death through accident or crime is increased, and the probability
of subsequent identification diminished. There is a possibility not too
remote to be disregarded, especially in times of war, of a harmless person
being arrested by mistake for another man, and being in sore straits to
give satisfactory proof of the error. A signature may be distrusted as a
forgery. There is also some small chance, when he returns to his own
country after a long absence, of finding difficulty in proving who he is.
But in civilised lands and in peaceable times, the chief use of a sure
means of identification is to benefit society by detecting rogues, rather
than to establish the identity of men who are honest. Is this criminal an
old offender? Is this new recruit a deserter? Is this professed pensioner
personating a man who is dead? Is this upstart claimant to property the
true heir, who was believed to have died in foreign lands?

In India and in many of our Colonies the absence of satisfactory means for
identifying persons of other races is seriously felt. The natives are
mostly unable to sign; their features are not readily distinguished by
Europeans; and in too many cases they are characterised by a strange
amount of litigiousness, wiliness, and unveracity. The experience of Sir
W. Herschel, and the way in which he met these unfavourable conditions by
the method of finger prints, has been briefly described in p. 27. Lately
Major Ferris, of the Indian Staff Corps, happening to visit my laboratory
during my absence, and knowing but little of what Sir W. Herschel had
done, was greatly impressed by the possibilities of finger prints. After
acquainting himself with the process, we discussed the subject together,
and he very kindly gave me his views for insertion here. They are as
follow, with a few trifling changes of words:--

    "During a period of twenty-three years, eighteen of which have been
    passed in the Political Department of the Bombay Government, the great
    need of an official system of identification has been constantly
    forced on my mind.

    "The uniformity in the colour of hair, eyes, and complexion of the
    Indian races renders identification far from easy, and the difficulty
    of recording the description of an individual, so that he may be
    afterwards recognised, is very great. Again, their hand-writing,
    whether it be in Persian or Devanagri letters, is devoid of character
    and gives but little help towards identification.

    "The tenacity with which a native of India cleaves to his ancestral
    land, his innate desire to acquire more and more, and the obligation
    that accrues to him at birth of safeguarding that which has already
    been acquired, amounts to a religion, and passes the comprehension of
    the ordinary Western mind. This passion, or religion, coupled with a
    natural taste for litigation, brings annually into the Civil Courts an
    enormous number of suits affecting land. In a native State at one time
    under my political charge, the percentage of suits for the possession
    of land in which the title was disputed amounted to no less than 92,
    while in 83 per cent of these the writing by which the transfer of
    title purported to have been made, was repudiated by the former
    title-holder as fraudulent and not executed by him. When it is
    remembered that an enormous majority of the landholders whose titles
    come into court are absolutely illiterate, and that their execution of
    the documents is attested by a mark made by a third party, frequently,
    though not always apparently, interested in the transfer, it will be
    seen that there is a wide door open to fraud, whether by false
    repudiation or by criminal attempt at dispossession.

    "It has frequently happened in my experience that a transfer of title
    or possession was repudiated; the person purporting to have executed
    the transfer asserting that he had no knowledge of it, and never
    authorised any one to write, sign, or present it for registration.
    This was met by a categorical statement on the part of the beneficiary
    and of the attesting witnesses, concerning the time, date, and
    circumstances of the execution and registration, that demolished the
    simple denial of the man whom it was sought to dispossess. Without
    going into the ethics of falsehood among Western and Eastern peoples,
    it would be impossible to explain how what is repugnant to the one as
    downright lying, is very frequently considered as no more than venial
    prevarication by the other. This, however, is too large a subject for
    present purposes, but the fact remains that perjury is perpetrated in
    Indian Courts to an extent unknown in the United Kingdom.

    "The interests of landholders are partially safeguarded by the Act
    that requires all documents effecting the transfer of immovable
    property to be registered, but it could be explained, though not in
    the short space of this letter, how the provisions of the Act can be,
    and frequently are, fulfilled in the absence of the principal person,
    the executor.

    "Enough has been said to show that if some simple but efficient means
    could be contrived to identify the person who has executed a bond,
    cases of fraud such as these would practically disappear from the
    judicial registers. Were the legislature to amend the Registration Act
    and require that the original document as well as the copy in the
    Registration Book should bear the imprint of one or more fingers of
    the parties to the deed, I have little hesitation in saying that not
    only would fraud be detected, but that in a short time the facility of
    that detection would act as a deterrent for the future. [This was
    precisely the experience of Sir W. Herschel.--F.G.] In the majority of
    cases, the mere question would be, Is the man A the same person as B,
    or is he not? and of that question the finger marks would give
    unerring proof. For example, to take the simplest case, A is sued for
    possession of some land, the title of which he is stated to have
    parted with to another for a consideration. The document and the
    Registration Book both bear the imprint of the index finger of the
    right hand of A. A repudiates, and a comparison shows that whereas
    the finger pattern of A is a whorl, the imprint on the document is a
    loop; consequently A did not execute it.

    "In the identification of Government pensioners the finger print
    method would be very valuable. At one period, I had the payment of
    many hundreds of military pensioners. Personation was most difficult
    to detect in persons coming from a distance, who had no local
    acquaintances, and more especially where the claimants were women. The
    marks of identification noted in the pension roll were usually
    variations of:--"Hair black--Eyes brown--Complexion wheat
    colour--Marks of tattooing on fore-arm"--terms which are equally
    appropriate to a large number of the pensioners. The description was
    supplemented in some instances, where the pensioner had some
    distinguishing mark or scar, but such cases are considerably rarer
    than might be supposed, and in women the marks are not infrequently in
    such a position as to practically preclude comparison. Here also the
    imprint of one or more finger prints on the pension certificate, would
    be sufficient to settle any doubt as to identity.

    "As a large number of persons pass through the Indian gaols not only
    while undergoing terms of imprisonment, but in default of payment of a
    fine, it could not but prove of value were the finger prints of one
    and all secured. They might assist in identifying persons who have
    formerly been convicted, of whom the local police have no knowledge,
    and who bear a name that may be the common property of half a hundred
    in any small town."

Whatever difficulty may be felt in the identification of Hindoos, is
experienced in at least an equal degree in that of the Chinese residents
in our Colonies and Settlements, who to European eyes are still more alike
than the Hindoos, and in whose names there is still less variety. I have
already referred (p. 26) to Mr. Tabor, of San Francisco, and his proposal
in respect to the registration of the Chinese. Remarks showing the need
of some satisfactory method of identifying them, have reached me from
various sources. The _British North Borneo Herald_, August 1, 1888, that
lies before me as I write, alludes to the difficulty of identifying
coolies, either by photographs or measurements, as likely to become
important in the early future of that country.

For purposes of registration, the method of printing to be employed, must
be one that gives little trouble on the one hand, and yields the maximum
of efficiency for that amount of trouble on the other. Sir W. Herschel
impressed simultaneously the fore and middle fingers of the right hand. To
impress simultaneously the fore, middle, and ring-fingers of the right
hand ought, however, to be better, the trouble being no greater, while
three prints are obviously more effective than two, especially for an
off-hand comparison. Moreover, the patterns on the ring-finger are much
more variable than those on the middle finger. Much as rolled impressions
are to be preferred for minute and exhaustive comparisons, they would
probably be inconvenient for purposes of registration or attestation. Each
finger has to be rolled separately, and each separate rolling takes more
time than a dab of all the fingers of one hand simultaneously. Now a
dabbed impression of even two fingers is more useful for registration
purposes than the rolled impression of one; much more is a dabbed
impression of three, especially when the third is the variable
ring-finger. Again, in a simultaneous impression, there is no doubt as to
the sequence of the finger prints being correct, but there may be some
occasional bungling when the fingers are printed separately.

       *       *       *       *       *

For most criminal investigations, and for some other purposes also, the
question is not the simple one just considered, namely, "Is A the same
person, or a different person from B?" but the much more difficult problem
of "Who is this unknown person X? Is his name contained in such and such a
register?" We will now consider how this question may be answered.

Registers of criminals are kept in all civilised countries, but in France
they are indexed according to the method of M. Alphonse Bertillon, which
admits of an effective search being made through a large collection. We
shall see how much the differentiating power of the French or of any other
system of indexing might be increased by including finger prints in the
register.

M. Bertillon has described his system in three pamphlets:--

    (1) _Une application pratique de l'anthropometrie_, Extrait des
    Annales de Démographie Interne. Paris 1881. (2) _Les signalements
    anthropometriques_, Conference faite au Congrès Penitentiare
    International de Rome, Nov. 22, 1885. (3) _Sur le fonctionnement du
    service des signalements_. All the above are published by Masson, 120
    Boulevard St. Germain, Paris. To these must be added a very
    interesting but anonymous pamphlet, based on official documents, and
    which I have reason to know is authorised by M. Bertillon, namely, (4)
    _L'anthropometrie Judiciare en Paris, en 1889_: G. Stenheil, 2 Rue
    Casimir-Delavigne, Paris.

    Besides these a substantial volume is forthcoming, which may give a
    satisfactory solution to some present uncertainties.

The scale on which the service is carried on, is very large. It was begun
in 1883, and by the end of 1887 no less than 60,000 sets of measures were
in hand, but thus far only about one half of the persons arrested in Paris
were measured, owing to the insufficiency of the staff. Arrangements were
then made for its further extension. There are from 100 to 150 prisoners
sentenced each day by the Courts of Law in Paris to more than a few days'
imprisonment, and every one of these is sent to the Dépôt for twenty-four
hours. While there, they are now submitted to _Bertillonage_, a newly
coined word that has already come into use. This is done in the forenoon,
by three operators and three clerks; six officials in all. About half of
the prisoners are old offenders, of whom a considerable proportion give
their names correctly, as is rapidly verified by an alphabetically
arranged catalogue of cards, each of which contains front and profile
photographs, and measurements. The remainder are examined strictly; their
bodily marks are recorded according to a terse system of a few letters,
and they are variously measured. Each person occupies seven or eight
minutes. They are then photographed. From sixty to seventy-five prisoners
go through this complete process every forenoon. In the afternoon the
officials are engaged in making numerous copies of each set of records,
one of which is sent to Lyon, and another to Marseille, where there are
similar establishments. They also classify the copies of records that are
received from those towns and elsewhere in France, of which from seventy
to one hundred arrive daily. Lastly, they search the Registers for
duplicate sets of measures of those, whether in Paris or in the provinces,
who were suspected of having given false names. The entire staff consists
of ten persons. It is difficult to rightly interpret the figures given in
the pamphlet (4) at pp. 22-24, as they appear to disagree, but as I
understand them, 562 prisoners who gave false names in the year 1890 were
recognised by _Bertillonage_, and only four other persons were otherwise
discovered to have been convicted previously, who had escaped recognition
by its means.

I had the pleasure of seeing the system in operation in Paris a few years
ago, and was greatly impressed by the deftness of the measuring, and with
the swiftness and success with which the assistants searched for the cards
containing entries similar to the measures of the prisoner then under
examination.

It is stated in the _Signalements_ (p. 12) that the basis of the
classification are the four measurements (1) Head-length, (2)
Head-breadth, (3) Middle-finger-length, (4) Foot-length, their constancy
during adult life nearly always [as stated] holding good. Each of these
four elements severally is considered as belonging to one or other of
three equally numerous classes--small, medium, and large; consequently
there are 3{4} or 81 principal headings, under some one of which the card
of each prisoner is in the first instance sorted. Each of these primary
headings is successively subdivided, on the same general principle of a
three-fold classification, according to other measures that are more or
less subject to uncertainties, namely, the height, the span, the cubit,
the length and breadth of the ear, and the height of the bust. The
eye-colour alone is subjected to seven divisions. The general result is
(pp. 19, 22) that a total of twelve measures are employed, of which eleven
are classed on the three-fold principle, and one on the seven-fold, giving
a final result of 3{11} × 7, or more than a million possible combinations.
M. Bertillon considers it by no means necessary to stop here, but in his
chapter (p. 22) on the "Infinite Extension of the Classification," claims
that the method may be indefinitely extended.

The success of the system is considered by many experts to be fully
proved, notwithstanding many apparent objections, one of which is the
difficulty due to transitional cases: a belief in its success has
certainly obtained a firm hold upon the popular imagination in France. Its
general acceptance elsewhere seems to have been delayed in part by a
theoretical error in the published calculations of its efficiency: the
measures of the limbs which are undoubtedly correlated being treated as
independent, and in part by the absence of a sufficiently detailed account
of the practical difficulties experienced in its employment. Thus in the
_Application pratique_, p. 9: "We are embarrassed what to choose, the
number of human measures which vary independently of each other being
considerable." In the _Signalements_, p. 19: "It has been shown" (by
assuming this independent variability) "that by seven measurements, 60,000
photographs can be separated into batches of less than ten in each." (By
the way, even on that assumption, the result is somewhat exaggerated, the
figures having been arrived at by successively taking the higher of the
two nearest round values.) In short, the general tone of these two memoirs
is one of enthusiastic belief in the method, based almost wholly, so far
as is there shown, on questionable _theoretic_ grounds of efficiency.

To learn how far correlation interferes with the regularity of
distribution, causing more entries to be made under some index-heads than
others, as was the case with finger prints, I have classified on the
Bertillon system, 500 sets of measures taken at my laboratory. It was not
practicable to take more than three of the four primary measures, namely,
the head-length, its breadth, and the middle-finger-length. The other
measure, that of foot-length, is not made at my laboratory, as it would
require the shoes to be taken off, which is inconvenient since persons of
all ranks and both sexes are measured there; but this matters little for
the purpose immediately in view. It should, however, be noted that the
head-length and head-breadth have especial importance, being only slightly
correlated, either together or with any other dimension of the body. Many
a small man has a head that is large in one or both directions, while a
small man rarely has a large foot, finger, or cubit, and conversely with
respect to large men.

The following set of five measures of each of the 500 persons were then
tabulated: (1) head-length; (2) head-breadth; (3) span; (4) body-height,
that is the height of the top of the head from the seat on which the
person sits; (5) middle-finger-length. The measurements were to the
nearest tenth of an inch, but in cases of doubt, half-tenths were recorded
in (1), (2), and (5). With this moderate minuteness of measurement, it was
impossible so to divide the measures as to give better results than the
following, which show that the numbers in the three classes are not as
equal as desirable. But they nevertheless enable us to arrive at an
approximate idea of the irregular character of the distribution.

TABLE XVI.

  +-----------------------------------------------------------------------+
  |                |   Medium     |Nos. in the three classes respectively.|
  |   Dimensions   | measures in  |---------------------------------------|
  |    measured.   | inches and   |   -    |    0    |    +    |   Total. |
  |                |   tenths.    | below. | medium. |  above. |          |
  |----------------|--------------|--------|---------|---------|----------|
  |1. Head-length  |  7·5 to  7·7 |  101   |   191   |   208   |    500   |
  |2. Head-breadth |  6·0  "  6·1 |  173   |   201   |   126   |    500   |
  |3. Span         | 68·0  " 70·5 |  137   |   165   |   198   |    500   |
  |4. Body-height  | 35·0  " 36·0 |  139   |   168   |   193   |    500   |
  |5. Middle-finger|  4·5  "  4·6 |  180   |   176   |   144   |    500   |
  +-----------------------------------------------------------------------+

The distribution of the measures is shown in Table XVII.

TABLE XVII.

_Distribution of 500 sets of measures into classes. Each set consists of
five elements; each element is classed as + or above medium class; M, or
mediocre; -, or below medium class._

(Total number of classes is 3{5} = 243.)

  +----------------------------------------------------------------+
  | +---- 3 Span.  |                                               |
  | |              |                                               |
  | |  +--4 Body-  |       1 Head-length, 2 Head-breadth.          |
  | |  |    height.|                                               |
  | |  |           |                                               |
  | |  |  5 Middle-|-----------------------------------------------|
  | |  |  | finger.| 1 2  1 2  1 2 | 1 2  1 2  1 2 | 1 2  1 2  1 2 |
  | |  |  |        |---------------|---------------|---------------|
  | |  |  |        | - -  - M  - + | M -  M M  M + | + -  + M  + + |
  |----------------|---------------|---------------|---------------|
  | -  -  -        | 14    7    4  |  14   11   5  |  3    3    2  |
  |       M        |  -    2    -  |   2    4   1  |  -    2    4  |
  |       +        |  -    -    -  |   1    -   -  |  -    -    -  |
  |                |               |               |               |
  | -  M  -        |  5    2    2  |   7    4   2  |  1    4    3  |
  |       M        |  -    2    -  |   3    1   3  |  2    3    -  |
  |       +        |  -    -    -  |   -    -   -  |  -    -    2  |
  |                |               |               |               |
  | -  +  -        |  2    -    -  |   1    1   1  |  -    -    1  |
  |       M        |  -    2    -  |   -    -   -  |  -    1    1  |
  |       +        |  -    -    -  |   1    -   -  |  -    1    -  |
  |----------------|---------------|---------------|---------------|
  | M  -  -        |  4    -    1  |   3    4   3  |  1    2    2  |
  |       M        |  3    2    -  |   3    2   3  |  2    4    -  |
  |       +        |  -    -    -  |   -    1   2  |  -    1    -  |
  |                |               |               |               |
  | M  M  -        |  1    3    1  |   4    3   2  |  4    4    3  |
  |       M        |  5    3    -  |   7    5   2  |  2    6    5  |
  |       +        |  2    1    1  |   1    1   -  |  1    4    2  |
  |                |               |               |               |
  | M  +  -        |  2    1    1  |   5    2   -  |  -    2    2  |
  |       M        |  2    2    -  |   3    3   1  |  1    6    7  |
  |       +        |  -    -    1  |   2    -   -  |  3    2    2  |
  |----------------|---------------|---------------|---------------|
  | +  -  -        |  -    -    1  |   -    1   -  |  -    -    -  |
  |       M        |  1    -    -  |   1    2   -  |  1    3    -  |
  |       +        |  1    2    -  |   1    1   -  |  -    -    2  |
  |                |               |               |               |
  | +  M  -        |  1    -    1  |   3    2   -  |  -    -    2  |
  |       M        |  2    -    1  |   1    4   -  |  3    2    4  |
  |       +        |  2    1    -  |   2    4   1  |  4    6    3  |
  |                |               |               |               |
  | +  +  -        |  1    2    -  |   1    -   1  |  1    2    2  |
  |       M        |  -    1    -  |   5   10   3  |  3    8    9  |
  |       +        |  2    2    2  |  11   10   3  |  9   24   19  |
  +----------------------------------------------------------------+

The frequency with which 1, 2, 3, 4, etc., sets were found to fall under
the same index-heading, is shown in Table XVIII.

TABLE XVIII.

  +----------------------------------------------------+
  |  No. of sets  |                  |                 |
  |  under same   | Frequency of its | No. of entries. |
  | index-heading.|    occurrence.   |                 |
  |---------------|------------------|-----------------|
  |       0       |        83        |        0        |
  |       1       |        47        |       47        |
  |       2       |        47        |       94        |
  |       3       |        25        |       75        |
  |       4       |        16        |       64        |
  |       5       |         7        |       35        |
  |       6       |         3        |       18        |
  |       7       |         4        |       28        |
  |       8       |         1        |        8        |
  |       9       |         2        |       18        |
  |      10       |         2        |       20        |
  |      11       |         2        |       22        |
  |      14       |         2        |       28        |
  |      19       |         1        |       19        |
  |      24       |         1        |       24        |
  |----------------------------------------------------|
  |      Total entries                      500        |
  +----------------------------------------------------+

No example was found of 83, say of one-third, of the 243 possible
combinations. In one case no less than 24 sets fell under the same head;
in another case 19 did so, and there were two cases in which 14, 11, and
10 severally did the same. Thus, out of 500 sets (see the five bottom
lines in the last column of the above table) no less than 113 sets fell
into four classes, each of which included from 10 to 24 entries.

The 24 sets whose Index-number is + M, + + + admit of being easily
subdivided and rapidly sorted by an expert, into smaller groups, paying
regard to considerable differences only, in the head-length and
head-breadth. After doing this, two comparatively large groups remain,
with five cases in each, which require further analysis. They are as
follow, the height and eye-colour being added in each case, and brackets
being so placed as to indicate measures that do not differ to a sufficient
amount to be surely distinguished. No two sets are alike throughout, some
difference of considerable magnitude always occurring to distinguish them.
Nos. 2 and 3 come closest together, and are distinguished by eye-colour
alone.

TABLE XIX.

  Five cases of Head-length 8·0, and Head-breadth 6·1.

           Span.     Body.    Finger.   Height.     Eye-colour.

   1.     { 72·4      38·0      4·8     { 71·2     { br. grey
   2.     { 72·6    { 37·0    { 4·7     { 71·4     { br. grey
   3.     { 72·7    { 36·7    { 4·7     { 71·4       blue
   4.       73·9      36·4      5·0       70·7       brown
   5.       75·3      37·9      4·8       73·4       blue

  Five cases of Head-length 7·8, and Head-breadth 6·0.

   6.       70·8     37·8     { 4·7     { 70·0       brown
   7.     { 71·9     36·2     { 4·7     { 69·3       blue
   8.     { 72·4   { 37·2     { 4·7     { 68·4       brown
   9.       74·8   { 37·8       5·0       73·1       blue
  10.       79·9   { 37·3       5·3       75·6       blue grey

This is satisfactory. It shows that each one of the 500 sets may be
distinguished from all the others by means of only seven elements; for if
it is possible so to subdivide twenty-four entries that come under one
index-heading, we may assume that we could do so in the other cases where
the entries were fewer. The other measures that I possess--strength of
grasp and breathing capacity--are closely correlated with stature and
bulk, while eyesight and reaction-time are uncorrelated, but the latter
are hardly suited to test the further application of the Bertillon method.

It would appear, from these and other data, that a purely anthropometric
classification, irrespective of bodily marks and photographs, would enable
an expert to deal with registers of considerable size.

Bearing in mind that mediocrities differ less from one another than
members of either of the extreme classes, and would therefore be more
difficult to distinguish, it seems probable that with comparatively few
exceptions, _at least_ two thousand adults of the same sex might be
individualised, merely by means of twelve careful measures, on the
Bertillon system, making reasonable allowances for that small change of
proportions that occurs after the lapse of a few years, and for
inaccuracies of measurement. This estimate may be far below the truth, but
more cannot, I think, be safely inferred from the above very limited
experiment.

The system of registration adopted in the American army for tracing
suspected deserters, was described in a memoir contributed to the
"International Congress of Demography," held in London in 1891. The memoir
has so far been only published in the _Abstracts of Papers_, p. 233 (Eyre
and Spottiswoode). Its phraseology is unfortunately so curt as sometimes
to be difficult to understand; it runs as follows:--

    Personal identity as determined by scars and other body marks by
    Colonel Charles R. Greenleaf and Major Charles Smart, Medical
    Department, U.S. Army.

    Desertions from United States army believed to greatly exceed
    deserters, owing to repeaters.

    Detection of repeaters possible if all body marks of all recruits
    recorded, all deserters noted, and all recruits compared with previous
    deserters.

    In like manner men discharged for cause excluded from re-entry.

    Bertillon's anthropometric method insufficient before courts-martial,
    because possible inaccuracies in measurement, and because of allowable
    errors.

    But identity acknowledged following coincident indelible marks, when
    height, age, and hair fairly correspond.

    That is, Bertillon's collateral evidence is practically primary
    evidence for such purposes.

    There is used for each man an outline figure card giving anterior and
    posterior surfaces, divided by dotted lines into regions.

    These, showing each permanent mark, are filed alphabetically at the
    Surgeon-General's office, War Department.

    As a man goes out for cause, or deserts, his card is placed in a
    separate file.

    The cards of recruits are compared with the last-mentioned file.

    To make this comparison, a register in two volumes is opened, one for
    light-eyed and one for dark-eyed men. Each is subdivided into a fair
    number of pages, according to height of entrants, and each page is
    ruled in columns for body regions. Tattooed and non-tattooed men of
    similar height and eyes are entered on opposite pages. Recruits
    without tattoos are not compared with deserters with tattoos; but
    recruits with tattoos are compared with both classes.

    On the register S T B M, etc., are used as abbreviations for scar,
    tattoo, birth-mark, mole, etc.

    One inch each side of recorded height allowed for variation or
    defective measurement.

    When probability of identity appears, the original card is used for
    comparison.

    Owing to obstacles in inaugurating new system, its practical working
    began with 1891, and, to include May 1891 [= 5 months, F.G.], out of
    sixty-two cases of suspected fraud sixty-one proved real.

There was some interesting discussion, both upon this memoir and on a
verbal communication concerning the French method, that had been made by
M. Jacques Bertillon the statistician, who is a brother of its originator.
It appeared that there was room for doubt whether the anthropometric
method had received a fair trial in America, the measurements being made
by persons not specially trained, whereas in France the establishments,
though small, are thoroughly efficient.

There are almost always moles or birth-marks, serving for identification,
on the body of every one, and a record of these is, as already noted, an
important though subsidiary part of the Bertillon system. Body-marks are
noted in the English registers of criminals, and it is curious how large a
proportion of these men are tattooed and scarred. How far the body-marks
admit of being usefully charted on the American plan, it is difficult to
say, the success of the method being largely dependent on the care with
which they are recorded. The number of persons hitherto dealt with on the
American plan appears not to be very large. As observations of this class
require the person to be undressed, they are unsuitable for popular
purposes of identification, but the marks have the merit of serving to
identify at all ages, which the measurements of the limbs have not.

It seems strange that no register of this kind, so far as I know, takes
account of the teeth. If a man, on being first registered, is deficient in
certain teeth, they are sure to be absent when he is examined on a future
occasion. He may, and probably will in the meantime, have lost others, but
the fact of his being without specified teeth on the first occasion,
excludes the possibility of his being afterwards mistaken for a man who
still possesses them.

We will now separately summarise the results arrived at, in respect to the
two processes that may both be needed in order to effect an
identification.

First, as regards _search in an Index_.--Some sets of measures will give
trouble, but the greater proportion can apparently be catalogued with so
much certainty, that if a second set of measures of any individual be
afterwards taken, no tedious search will be needed to hunt out the former
set. Including the bodily marks and photographs, let us rate the Bertillon
method as able to cope with a register of 20,000 adults of the same sex,
with a small and definable, but as yet unknown, average dose of
difficulty, which we will call _x_.

A catalogue of 500 sets of finger prints easily fulfils the same
conditions. I could lay a fair claim to much more, but am content with
this. Now the finger patterns have been shown to be so independent of
other conditions that they cannot be notably, if at all, correlated with
the bodily measurements or with any other feature, not the slightest
trace of any relation between them having yet been found, as will be shown
at p. 186, and more fully in Chapter XII. For instance, it would be
totally impossible to fail to distinguish between the finger prints of
twins, who in other respects appeared exactly alike. Finger prints may
therefore be treated without the fear of any sensible error, as varying
quite independently of the measures and records in the Bertillon system.
Their inclusion would consequently increase its power fully five-hundred
fold. Suppose one moderate dose of difficulty, _x_, is enough for dealing
with the measurements, etc., of 20,000 adult persons of the same sex by
the Bertillon method, and a similar dose of difficulty with the finger
prints of 500 persons, then two such doses could deal with a register of
20,000 × 500, or 10,000,000.

We now proceed to consider the second and final process, namely, that of
identification by _Comparison_. When the data concerning a suspected
person are discovered to bear a general likeness to one of those already
on the register, and a minute comparison shows their finger prints to
agree in all or nearly all particulars, the evidence thereby afforded that
they were made by the same person, far transcends in trustworthiness any
other evidence that can ordinarily be obtained, and vastly exceeds all
that can be derived from any number of ordinary anthropometric data. _By
itself it is amply sufficient to convict._ _Bertillonage_ can rarely
supply more than grounds for very strong suspicion: the method of finger
prints affords certainty. It is easy, however, to understand that so long
as the peculiarities of finger prints are not generally understood, a
juryman would be cautious in accepting their evidence, but it is to be
hoped that attention will now gradually become drawn to their marvellous
virtues, and that after their value shall have been established in a few
conspicuous cases, it will come to be popularly recognised.

Let us not forget two great and peculiar merits of finger prints; they are
self-signatures, free from all possibility of faults in observation or of
clerical error; and they apply throughout life.

An abstract of the remarks made by M. Herbette, Director of the
Penitentiary Department of the Ministère de l'Intérieur, France, at the
International Penitentiary Congress at Rome, after the communication by M.
Alphonse Bertillon had been read, may fitly follow.

    "Proceeding to a more extended view of the subject and praising the
    successful efforts of M. Bertillon, M. Herbette pointed out how a
    verification of the physical personality, and of the identity of
    people of adult age, would fulfil requirements of modern society in an
    indisputable manner under very varied conditions.

    "If it were a question, for instance, of giving to the inhabitants of
    a country, to the soldiers of an army, or to travellers proceeding to
    distant lands, notices or personal cards as recognisable signs,
    enabling them always to prove who they are; if it were a question of
    completing the obligatory records of civil life by perfectly sure
    indications, such as would prevent all error, or substitution of
    persons; if it were a question of recording the distinctive marks of
    an individual in documents, titles or contracts, where his identity
    requires to be established for his own interest, for that of third
    parties, or for that of the State,--there the anthropometric system
    of identification would find place.

    "Should it be a question of a life certificate, of a life assurance,
    or of a proof of death, or should it be required to certify the
    identity of a person who was insane, severely wounded, or of a dead
    body that had been partly destroyed, or so disfigured as to be hardly
    recognisable from a sudden or violent death due to crime, accident,
    shipwreck, or battle--how great would be the advantage of being able
    to trace these characters, unchangeable as they are in each
    individual, infinitely variable as between one individual and another,
    indelible, at least in part, even in death.

    "There is still more cause to be interested in this subject when it is
    a question of identifying persons who are living at a great distance,
    and after the lapse of a considerable time, when the physiognomy, the
    features, and the physical habits may have changed from natural or
    artificial causes, and to be able to identify them without taking a
    journey and without cost, by the simple exchange of a few lines or
    figures that may be sent from one country or continent to another, so
    as to give information in America as to who any particular man is, who
    has just arrived from France, and to certify whether a certain
    traveller found in Rome is the same person who was measured in
    Stockholm ten years before.

    "In one word, to fix the human personality, to give to each human
    being an identity, an individuality that can be depended upon with
    certainty, lasting, unchangeable, always recognisable and easily
    adduced, this appears to be in the largest sense the aim of the new
    method.

    "Consequently, it may be said that the extent of the problem, as well
    as the importance of its solution, far exceeds the limits of
    penitentiary work and the interest, which is however by no means
    inconsiderable, that penal action has excited amongst various nations.
    These are the motives for giving to the labours of M. Bertillon and to
    their practical utilisation the publicity they merit."

These full and clear remarks seem even more applicable to the method of
finger prints than to that of anthropometry.




CHAPTER XI

HEREDITY


Some of those who have written on finger marks affirm that they are
transmissible by descent, others assert the direct contrary, but no
inquiry hitherto appears to justify a definite conclusion.

Chapter VIII. shows a close correlation to exist between the patterns on
the several fingers of the same person. Hence we are justified in assuming
that the patterns are partly dependent on constitutional causes, in which
case it would indeed be strange if the general law of heredity failed in
this particular case.

After examining many prints, the frequency with which some peculiar
pattern was found to characterise members of the same family convinced me
of the reality of an hereditary tendency. The question was how to submit
the belief to numerical tests; particular kinships had to be selected, and
methods of discussion devised.

It must here be borne in mind that "Heredity" implies more than its
original meaning of a relationship between parent and child. It includes
that which connects children of the same parents, and which I have shown
(_Natural Inheritance_) to be just twice as close in the case of stature
as that which connects a child and either of its two parents. Moreover,
the closeness of the fraternal and the filial relations are to a great
extent interdependent, for in any population whose faculties remain
_statistically_ the same during successive generations, it has been shown
that a simple algebraical equation must exist, that connects together the
three elements of Filial Relation, Fraternal Relation, and Regression, by
which a knowledge of any two of them determines the value of the third. So
far as Regression may be treated as being constant in value, the Filial
and the Fraternal relations become reciprocally connected. It is not
possible briefly to give an adequate explanation of all this now, or to
show how strictly observations were found to confirm the theory; this has
been fully done in _Natural Inheritance_, and the conclusions will here be
assumed.

The fraternal relation, besides disclosing more readily than other
kinships the existence or non-existence of heredity, is at the same time
more convenient, because it is easier to obtain examples of brothers and
sisters alone, than with the addition of their father and mother. The
resemblance between those who are twins is also an especially significant
branch of the fraternal relationship. The word "fraternities" will be used
to include the children of both sexes who are born of the same parents; it
being impossible to name the familiar kinship in question either in
English, French, Latin, or Greek, without circumlocution or using an
incorrect word, thus affording a striking example of the way in which
abstract thought outruns language, and its expression is hampered by the
inadequacy of language. In this dilemma I prefer to fall upon the second
horn, that of incorrectness of phraseology, subject to the foregoing
explanation and definition.

The first preliminary experiments were made with the help of the
Arch-Loop-Whorl classification, on the same principle as that already
described and utilised in Chapter VIII., with the following addition. Each
of the two members of any couplet of fingers has a distinctive name--for
instance, the couplet may consist of a finger and a thumb: or again, if it
should consist of two fore-fingers, one will be a right fore-finger and
the other a left one, but the two brothers in a couplet of brothers rank
equally as such. The plan was therefore adopted of "ear-marking" the
prints of the first of the two brothers that happened to come to hand,
with an A, and that of the second brother with a B; and so reducing the
questions to the shape:--How often does the pattern on the finger of a B
brother agree with that on the corresponding finger of an A brother? How
often would it occur between two persons who had no family likeness? How
often would it correspond if the kinship between A and B were as close as
it is possible to conceive? Or transposing the questions, and using the
same words as in Chapter VIII., what is the relative frequency of (1)
Random occurrences, (2) Observed occurrences, (3) Utmost possibilities?
It was shown in that chapter how to find the value of (2) upon a
centesimal scale in which "Randoms" ranked as 0° and "Utmost
possibilities" as 100°.

The method there used of calculating the frequency of the "Random" events
will be accepted without hesitation by all who are acquainted with the
theory and the practice of problems of probability. Still, it is as well
to occasionally submit calculation to test. The following example was sent
to me for that purpose by a friend who, not being mathematically minded,
had demurred somewhat to the possibility of utilising the calculated
"Randoms."

The prints of 101 (by mistake for 100) couplets of prints of the right
fore-fingers of school children were taken by him from a large collection,
the two members, A and B, being picked out at random and formed into a
couplet. It was found that among the A children there were 22 arches, 50
loops, and 29 whorls, and among the B children 25, 34, and 42
respectively, as is shown by the _italic_ numerals in the last column, and
again in the bottom row of Table XX. The remainder of the table shows the
number of times in which an arch, loop, or whorl of an A child was
associated with an arch, loop, or whorl of a B child.

TABLE XX.

_Observed Random Couplets._

  +----------------------------------------------------+
  |             |       A children.      |  Totals in  |
  | B children. |------------------------| B children. |
  |             | Arches.| Loops.|Whorls.|             |
  |-------------|--------|-------|-------|-------------|
  | Arches      |    5   |   12  |    8  |     _25_    |
  | Loops       |    8   |   18  |    8  |     _34_    |
  | Whorls      |    9   |   20  |   13  |     _42_    |
  |-------------|--------|-------|-------|-------------|
  |Totals in A} |        |       |       |             |
  |  children } |  _22_  |  _50_ |  _29_ |     101     |
  +----------------------------------------------------+

TABLE XXI.

_Calculated Random Couplets._

  +----------------------------------------------------+
  |             |       A children.      |  Totals in  |
  | B children. |------------------------| B children. |
  |             | Arches.| Loops.|Whorls.|             |
  |-------------|--------|-------|-------|-------------|
  | Arches      |  5·00  | 12·50 |  7·25 |     _25_    |
  | Loops       |  6·80  | 17·00 |  9·86 |     _34_    |
  | Whorls      |  8·40  | 21·00 | 12·18 |     _42_    |
  |-------------|--------|-------|-------|-------------|
  |Totals in A} |        |       |       |             |
  |  children } |  _22_  |  _50_ |  _29_ |     101     |
  +----------------------------------------------------+

The question, then, was how far calculations from the above data would
correspond with the contents of Table XX. The answer is that it does so
admirably. Multiply each of the italicised A totals into each of the
italicised B totals, and after dividing each result by 101, enter it in
the square at which the column that has the A total at its base, is
intersected by the row that has the B total at its side. We thus obtain
Table XXI.

We will now discuss in order the following relationships: the Fraternal,
first in the ordinary sense, and then in the special case of twins of the
same set; Filial, in the special case in which both parents have the same
particular pattern on the same finger; lastly, the relative influence of
the father and mother in transmitting their patterns.

_Fraternal relationship._--In 105 fraternities the _observed_ figures were
as in Table XXII.:--

TABLE XXII.

_Observed Fraternal Couplets._

  +----------------------------------------------------+
  |              |      A children.     |   Totals in  |
  | B children.  |----------------------|  B children. |
  |              |Arches.|Loops.|Whorls.|              |
  |--------------|-------|------|-------|--------------|
  |Arches        |   5   |  12  |   2   |      _19_    |
  |              |-------+------|       |              |
  |Loops         |   4   |  42  |  15   |      _61_    |
  |              |-------|------|-------|              |
  |Whorls        |   1   |  14  |  10   |      _25_    |
  |--------------|-------+------+-------|--------------|
  |Totals in A } |       |      |       |              |
  |  children  } | _10_  | _68_ | _27_  |      105     |
  +----------------------------------------------------+

The squares that run diagonally from the top at the left, to the bottom at
the right, contain the double events, and it is with these that we are
now concerned. Are the entries in those squares larger or not than the
randoms, calculated as above, viz. the values of 10 × 19, 68 × 61, 27 ×
25, all divided by 105? The calculated Randoms are shown in the first line
of Table XXIII., the third line gives the greatest feasible number of
correspondences which would occur if the kinship were as close as
possible, subject to the reservation explained in p. 127. As there shown,
the _lower_ of the A and B values is taken in each case, for Arches,
Loops, and Whorls respectively.

TABLE XXIII.

  +----------------------------------------------+
  |                 |    A and B both being      |
  |                 |----------------------------|
  |                 | Arches. | Loops. | Whorls. |
  |-----------------|---------|--------|---------|
  | Random          |   1·7   |  37·6  |   6·2   |
  | Observed        |   5·0   |  42·0  |  10·0   |
  | Utmost feasible |  10·0   |  61·0  |  25·0   |
  +----------------------------------------------+

In every instance, the Observed values are seen to exceed the Random.

Many other cases of this description were calculated, all yielding the
same general result, but these results are not as satisfactory as can be
wished, owing to their dilution by inappropriate cases, the A. L. W.
system being somewhat artificial.


[Illustration: PLATE 16.

FIG. 24. The "C" set of standard patterns, for prints of the Right Hand.]


With the view of obtaining a more satisfactory result the patterns were
subdivided under fifty-three heads, and an experiment was made with the
fore, middle, and ring-fingers of 150 fraternal couplets (300
individuals and 900 digits) by Mr. F. Howard Collins, who kindly undertook
the considerable labour of indexing and tabulating them.

The provisional list of standard patterns published in the _Phil. Trans._
was not appropriate for this purpose. It related chiefly to thumbs, and
consequently omitted the tented arch; it also referred to the left hand,
but in the following tabulations the right hand has been used; and its
numbering is rather inconvenient. The present set of fifty-three patterns
has faults, and cannot be considered in any way as final, but it was
suitable for our purposes and may be convenient to others; as Mr. Collins
worked wholly by it, it may be distinguished as the "C. set." The banded
patterns, 24-31, are very rarely found on the fingers, but being common on
the thumb, were retained, on the chance of our requiring the introduction
of thumb patterns into the tabulations. The numerals refer to the patterns
as seen in impressions of the _right hand_ only. [They would be equally
true for the patterns as seen on the _fingers themselves_ of the left
hand.] For impressions of the left hand the numerals up to 7 inclusive
would be the same, but those of all the rest would be changed. These are
arranged in couplets, the one member of the couplet being a reversed
picture of the other, those in each couplet being distinguished by
severally bearing an odd and an even number. Therefore, in impressions of
the left hand, 8 would have to be changed into 9, and 9 into 8; 10 into
11, and 11 into 10; and so on, up to the end, viz. 52 and 53. The numeral
54 was used to express nondescript patterns.

The finger prints had to be gone through repeatedly, some weeks elapsing
between the inspections, and under conditions which excluded the
possibility of unconscious bias; a subject of frequent communication
between Mr. Collins and myself. Living at a distance apart, it was not
easy at the time they were made, to bring our respective interpretations
of transitional and of some of the other patterns, especially the invaded
loops, into strict accordance, so I prefer to keep his work, in which I
have perfect confidence, independent from my own. Whenever a fraternity
consisted of more than two members, they were divided, according to a
prearranged system, into as many couplets as there were individuals. Thus,
while a fraternity of three individuals furnished all of its three
possible varieties of couplets, (1, 2), (1, 3), (2, 3), one of four
individuals was not allowed to furnish more than four of its possible
couplets, the two italicised ones being omitted, (1, 2), (1, 3), (_1, 4_),
(_2, 3_), (2, 4), (3, 4), and so on. Without this precaution, a single
very large family might exercise a disproportionate and even overwhelming
statistical influence.

It would be essential to exact working, that the mutual relations of the
patterns should be taken into account; for example, suppose an arch to be
found on the fore-finger of one brother and a nascent loop on that of the
other; then, as these patterns are evidently related, their concurrence
ought to be interpreted as showing some degree of resemblance. However,
it was impossible to take cognizance of partial resemblances, the mutual
relations of the patterns not having, as yet, been determined with
adequate accuracy.

The completed tabulations occupied three large sheets, one for each of the
fingers, ruled crossways into fifty-three vertical columns for the A
brothers, and fifty-three horizontal rows for the B brothers. Thus, if the
register number of the pattern of A was 10, and that of B was 42, then a
mark would be put in the square limited by the ninth and tenth horizontal
lines, and by the forty-first and forty-second vertical ones. The marks
were scattered sparsely over the sheet. Those in each square were then
added up, and finally the numbers in each of the rows and in each of the
columns were severally totalled.

If the number of couplets had been much greater than they are, a test of
the accuracy with which their patterns had been classed under the
appropriate heads, would be found in the frequency with which the same
patterns were registered in the corresponding finger of the A and B
brothers. The A and B groups are strictly homogeneous, consequently the
frequency of their patterns in corresponding fingers ought to be alike.
The success with which this test has been fulfilled in the present case,
is passably good, its exact degree being shown in the following
paragraphs, where the numbers of entries under each head are arranged in
as orderly a manner as the case admits, the smaller of the two numbers
being the one that stands first, whether it was an A or a B. All instances
in which there were at least five entries under either A or B, are
included; the rest being disregarded. The result is as follows:--

    I. Thirteen cases of more or less congruity between the number of A
    and B entries under the same head:--5-7; 5-7; 5-8; 6-8; 7-10; 8-9;
    8-12; 9-12; 10-10; 11-13; 12-16; 14-18; 72-73. (This last refers to
    loops on the middle finger.)

    II. Six cases of more or less incongruity:--1-7; 6-12; 14-20; 14-22;
    22-35; 39-50.

The three Tables, XXIV., XXV., XXVI., contain the results of the
tabulations and the deductions from them.

TABLE XXIV.

_Comparison of three Fingers of the Right Hand in 150 Fraternal Couplets._

  +------------------------------------------------------------------------+
  |       |   Fore-fingers.    ||   Middle fingers.  ||    Ring-fingers.   |
  |       |--------------------||--------------------||--------------------|
  | Index |  Down |Along|Double||  Down |Along|Double||  Down |Along|Double|
  | No. of|columns|lines|events||columns|lines|events||columns|lines|events|
  |Pattern|-------|-----|------||-------|-----|------||-------|-----|------|
  |       |       |     |   A  ||       |     |   A  ||       |     |   A  |
  |       |   A   |  B  |  and ||   A   |  B  |  and ||   A   |  B  |  and |
  |       |       |     |   B  ||       |     |   B  ||       |     |   B  |
  |-------|-------|-----|------||-------|-----|------||-------|-----|------|
  |    1  |  15   | 12  |   4  ||   8   |  5  |   2  ||   7   |  5  |   1  |
  |    2  |   3   |  2  |      ||   3   |  2  |      ||       |     |      |
  |    6  |   2   |  2  |   1  ||       |     |      ||   2   |  4  |      |
  |    7  |       |  2  |      ||   2   |  1  |      ||   7   |  5  |   1  |
  |    8  |       |     |      ||       |     |      ||       |  1  |      |
  |    9  |   1   |  7  |      ||   4   |  1  |   1  ||   7   |  1  |      |
  |   12  |   1   |     |      ||   2   |     |      ||       |     |      |
  |   13  |       |     |      ||   2   |  1  |      ||       |     |      |
  |   14  |   4   |  3  |      ||   4   |  4  |   1  ||  20   | 14  |   1  |
  |   15  |  16   | 12  |   3  ||   4   |  2  |      ||   3   |  4  |      |
  |   16  |   2   |  3  |      ||   2   |  3  |      ||  10   |  7  |   2  |
  |   17  |   4   |  3  |      ||   3   |     |      ||       |     |      |
  |   18  |       |     |      ||   4   |  1  |      ||  18   | 14  |   6  |
  |   19  |   3   |  3  |      ||   2   |  5  |      ||   1   |     |      |
  |   20  |       |     |      ||       |     |      ||   1   |  3  |   1  |
  |   21  |       |  1  |      ||       |     |      ||       |     |      |
  |   22  |       |  4  |      ||   1   |  8  |      ||   1   |  2  |      |
  |   23  |   1   |     |      ||   1   |     |      ||   6   |     |      |
  |   27  |   1   |     |      ||       |     |      ||       |     |      |
  |   32  |   1   |     |      ||   1   |  3  |      ||   4   |  4  |      |
  |   33  |   3   |  1  |   1  ||   1   |     |      ||   3   |  3  |   1  |
  |   34  |   3   |  2  |      ||   4   |  1  |      ||       |     |      |
  |   35  |   2   |  3  |      ||       |  5  |      ||   9   | 12  |   2  |
  |   38  |   2   |  1  |      ||       |     |      ||       |     |      |
  |   39  |   4   |     |      ||   3   |  1  |      ||       |     |      |
  |   40  |  13   | 11  |   1  ||  14   | 22  |   6  ||   9   |  8  |      |
  |   41  |  12   |  8  |      ||   1   |  3  |      ||       |  1  |      |
  |   42  |  22   | 35  |   5  ||  73   | 72  |  35  ||  39   | 50  |  16  |
  |   43  |  10   | 10  |   3  ||   4   |  1  |      ||       |  3  |      |
  |   44  |   2   |  1  |      ||       |  2  |      ||       |  2  |      |
  |   45  |   1   |  1  |      ||       |     |      ||       |     |      |
  |   46  |   8   |  6  |   1  ||   3   |  1  |      ||       |  1  |      |
  |   47  |   3   |  4  |      ||       |     |      ||       |     |      |
  |   48  |   6   | 12  |   1  ||   4   |  6  |      ||   2   |  3  |      |
  |   49  |   1   |  1  |      ||       |     |      ||       |     |      |
  |   52  |       |     |      ||       |     |      ||   1   |     |      |
  |   53  |       |     |      ||       |     |      ||       |  1  |      |
  +------------------------------------------------------------------------+

TABLE XXV.

_Comparison between Random and Observed Events._

  +-------------------------------------------------------------+
  |       Fore.       ||      Middle.      ||       Ring.       |
  |-------------------||-------------------||-------------------|
  | Random.| Observed.|| Random.| Observed.|| Random.| Observed.|
  |--------|----------||--------|----------||--------|----------|
  |  1·20  |     4    ||  0·26  |     2    ||  0·23  |     1    |
  |  0·08  |   ...    ||  0·11  |     1    ||  0·05  |   ...    |
  |  1·28  |     3    ||  0·05  |   ...    ||  0·23  |   ...    |
  |  0·08  |   ...    ||  0·07  |   ...    ||  1·87  |     1    |
  |  0·06  |   ...    ||  0·05  |   ...    ||  0·08  |   ...    |
  |  0·95  |     1    ||  2·05  |     6    ||  0·46  |     2    |
  |  0·64  |   ...    || 34·08  |    35    ||  1·68  |     6    |
  |  5·18  |     5    ||  0·16  |   ...    ||  0·11  |   ...    |
  |  0·67  |     3    ||        |          ||  0·06  |     1    |
  |  0·32  |     1    ||        |          ||  0·72  |     2    |
  |  0·08  |   ...    ||        |          ||  0·48  |   ...    |
  |  0·48  |     1    ||        |          || 13·00  |    16    |
  |--------|          ||        |          ||        |          |
  |   All  |          ||        |          ||        |          |
  | others.|          ||        |          ||        |          |
  |  0·29  |     2    ||  0·28  |     1    ||  0·12  |     1    |
  |--------|----------||--------|----------||--------|----------|
  | 11·31  |    20    || 37·11  |    45    || 19·09  |    30    |
  +-------------------------------------------------------------+

TABLE XXVI.

_Centesimal Scale (to nearest whole numbers)._

  +-----------------------------------------------------------------------+
  |150 fraternal|Random.|Observed.|    Utmost    |Reduced  |  Reduced to  |
  |  couplets.  |       |         |possibilities.|to lower |    upper     |
  |             |       |         |              |limit=0. |  limit=100.  |
  |-------------|-------|---------|--------------|---------|--------------|
  |             |       |         |              |         |  Centesimal  |
  |             |       |         |              |         |    scale.    |
  |             |       |         |              |         |--------------|
  |Fore-finger  | 11·31 |    20   |     115      |0  9 104 |0°  9°    100°|
  |Middle       | 37·11 |    45   |     117      |0 10  80 |0° 10°    100°|
  |Ring         | 19·09 |    31   |     118      |0 12  99 |0° 12°    100°|
  |-----------------------------------------------------------------------|
  |                                               Mean     |0° 10°    100°|
  |-----------------------------------------------------------------------|
  |50 additional|       |         |              |         |              |
  |  couplets.  |       |         |              |         |              |
  |-------------|       |         |              |         |              |
  |Middle finger|       |         |              |         |              |
  |only         |  8·2  |    11   |      22      |0  3  14 |0° 21°    100°|
  |-------------|-------|---------|--------------|---------|--------------|
  | Loops only, |       |         |              |         |              |
  |and on middle|       |         |              |         |              |
  | finger only.|       |         |              |         |              |
  |-------------|       |         |              |         |              |
  |150 couplets | 34·0  |    35   |      72      |0 1   72 |0° 1-1/4° 100°|
  |50 couplets  |  6·4  |     7   |      14      |0 0·6  8 |0° 8°     100°|
  +-----------------------------------------------------------------------+

Table XXIV. contains all the Observed events, and is to be read thus,
beginning at the first entry. Pattern No. 1 occurs on the right
fore-finger fifteen times among the A brothers, and twelve times among the
B brothers; while in four of these cases both brothers have that same
pattern.

Table XXV. compares the Random events with the Observed ones. Every case
in which the calculated expectation is equal to or exceeds 0·05, is
inserted in detail; the remaining group of petty cases are summed together
and their totals entered in the bottom line. For fear of misapprehension
or forgetfulness, one other example of the way in which the Randoms are
calculated will be given here, taking for the purpose the first entry in
Table XXIV. Thus, the number of all the different combinations of the 150
A with the 150 B individuals in the 150 couplets, is 150 × 150. Out of
these, the number of double events in which pattern No. 1 would appear in
the same combination, is 15 × 12 = 180. Therefore in 150 trials, the
double event of pattern No. 1 would appear upon the average, on 180
divided by 150, or on 1·20 occasions. As a matter of fact, it appeared
four times. These figures will be found in the first line of Table XXV.;
the rest of its contents have been calculated in the same way.

Leaving aside the Randoms that exceed 0 but are less than 1, there are
nineteen cases in which the Random may be compared with the Observed
values; in all but two of these the Observed are the highest, and in these
two the Random exceed the Observed by only trifling amounts, namely, 5·18
Random against 5·00 Observed; 1·87 Random against 1·00 Observed. It is
impossible, therefore, to doubt from the steady way in which the Observed
values overtop the Randoms, that there is a greater average likeness in
the finger marks of two brothers, than in those of two persons taken at
hazard.

Table XXVI. gives the results of applying the centesimal scale to the
measurement of the average closeness of fraternal resemblance, in respect
to finger prints, according to the method and under the reservations
already explained in page 125. The average value thus assigned to it is a
little more than 10°. The values obtained from the three fingers
severally, from which that average was derived, are 9°, 10°, and 12°; they
agree together better than might have been expected. The value obtained
from a set of fifty additional couplets of the middle fingers only, of
fraternals, is wider, being 21°. Its inclusion with the rest raises the
average of all to between 10 and 11.

In the pre-eminently frequent event of loops with an outward slope on the
middle finger, it is remarkable that the Random cases are nearly equal to
the Observed ones; they are 34·08 to 35·00. It was to obtain some
assurance that this equality was not due to statistical accident, that the
additional set of fifty couplets were tabulated. They tell, however, the
same tale, viz. 6·4 Randoms to 7·0 Observed. The loops on the fore-fingers
confirm this, showing 5·18 Randoms to 5·00 Observed; those on the
ring-finger have the same peculiarity, though in a slighter degree, 13 to
16: the average of other patterns shows a much greater difference than
that. I am unable to account for this curious behaviour of the loops,
which can hardly be due to statistical accident, in the face of so much
concurrent evidence.

_Twins._--The signs of heredity between brothers and sisters ought to be
especially apparent between twins of the same sex, who are physiologically
related in a peculiar degree and are sometimes extraordinarily alike. More
rarely, they are remarkably dissimilar. The instances of only a moderate
family resemblance between twins of the same sex are much less frequent
than between ordinary brothers and sisters, or between twins of opposite
sex. All this has been discussed in my _Human Faculty_. In order to test
the truth of the expectation, I procured prints of the fore, middle, and
ring-fingers of seventeen sets of twins, and compared them, with the
results shown in Table XXVII.

TABLE XXVII.

17 SETS OF TWINS (A and B).

_Comparison between the patterns on the Fore, Middle, and Ring-fingers
respectively of the Right hand._

Agreement (=), 19 cases; partial (··), 13 cases; disagreement (×), 19
cases.

  +----------------------------------------------------------------+
  |      | A     B  |    A     B  | A     B  | A     B  | A     B  |
  |----------------------------------------------------------------|
  |Fore  | 42 =  42 |    21 =  21 | 40 =  40 |  6 =   6 |  1 =   1 |
  |Middle| 42 =  42 |     8 =   8 | 32 ×  42 | 15 ·· 32 | 42 =  42 |
  |Ring  | 42 =  42 |     8 =   8 | 42 =  42 | 33 =  33 | 40 ×  19 |
  |      |          |             |          |          |          |
  |Fore  | 42 =  42 |    43 ×  15 |  1 =   1 | 15 ×  34 |  2 ·· 42 |
  |Middle| 42 =  42 |    42 ·· 40 |  1 ×  40 | 42 =  42 | 42 =  42 |
  |Ring  | 42 ·· 46 |    35 =  35 | 40 ·· 42 | 14 ×  32 | 42 ×  14 |
  |      |          |             |          |          |          |
  |Fore  | 49 ·· 14 |    15 ×  49 | 15 ·· 16 |  1 ×  42 |  1 ×  15 |
  |Middle| 42 =  42 |    23 ×  14 | 19 ×  42 | 42 ·· 48 | 32 ×  22 |
  |Ring  |  9 ·· 32 |    14 ·· 16 |  6 ·· 18 | 42 ×   8 | 18 ×  23 |
  |      |          |             |          |          |          |
  |Fore  | 48 ×  33 |(loop) ×   9 |          |          |          |
  |Middle| 42 ×  22 |    48 ×  22 |          |          |          |
  |Ring  | 14 ··  6 |     9 ·· 35 |          |          |          |
  +----------------------------------------------------------------+

The result is that out of the seventeen sets (=51 couplets), two sets
agree in all their three couplets of fingers; four sets agree in two; five
sets agree in one of the couplets. There are instances of partial
agreement in five others, and a disagreement throughout in only one of the
seventeen sets. In another collection of seventeen sets, made to compare
with this, six agreed in two of their three couplets, and five agreed in
one of them. There cannot then be the slightest doubt as to the strong
tendency to resemblance in the finger patterns in twins.

This remark must by no means be forced into the sense of meaning that the
similarity is so great, that the finger print of one twin might
occasionally be mistaken for that of the other. When patterns fall into
the same class, their general forms may be conspicuously different (see p.
74), while their smaller details, namely, the number of ridges and the
minutiæ, are practically independent of the pattern.

It may be mentioned that I have an inquiry in view, which has not yet been
fairly begun, owing to the want of sufficient data, namely to determine
the minutest biological unit that may be hereditarily transmissible. The
minutiæ in the finger prints of twins seem suitable objects for this
purpose.

_Children of like-patterned Parents._--When two parents are alike, the
average resemblance, in stature at all events, which their children bear
to them, is as close as the fraternal resemblance between the children,
and twice as close as that which the children bear to either parent
separately, when the parents are unlike.

The fifty-eight parentages affording fifty couplets of the fore, middle,
and ring-fingers respectively give 58 × 3 = 174 parental couplets in all;
of these, 27 or 14 per cent are alike in their pattern, as shown by Table
XXVIII. The total number of children to these twenty-seven pairs is 109,
of which 59 (or 54 per cent) have the same pattern as their parents. This
fact requires analysis, as on account of the great frequency of loops, and
especially of the pattern No. 42 on the middle finger, a large number of
the cases of similarity of pattern between child and parents would be mere
random coincidences.

TABLE XXVIII.--_Children of like-patterned Parents._

  +-------------------------------------------------------------------+
  | The 27 | Patterns of--  F.  M. |    --of Sons.   | Alike. | Total |
  | cases. |                       |                 |        | sons. |
  |--------|-----------------------|-----------------|--------|-------|
  |    1   | Fore            1   1 |  1              |    1   |   1   |
  |    2   |                34  34 | 34              |    1   |   1   |
  |    3   |                40  40 | 41              |   ...  |   1   |
  |    4   |                42  42 | 48              |   ...  |   1   |
  |        |                       |                 |        |       |
  |    5   | Middle         40  40 | 40              |    1   |   1   |
  |    6   |                42  42 | 42              |    1   |   1   |
  |    7   |                42  42 | 42              |    1   |   1   |
  |    8   |                42  42 | 42, 38, 42, 42  |    3   |   4   |
  |    9   |                42  42 | 42              |    1   |   1   |
  |   10   |                42  42 | 48, 48, 14      |    1   |   4   |
  |   11   |                42  42 | 42              |    1   |   1   |
  |   12   |                42  42 | 40              |   ...  |   1   |
  |   13   |                42  42 |  1              |   ...  |   1   |
  |   14   |                42  42 | 42              |    1   |   1   |
  |   15   |                42  42 | 42, 46, 42      |    2   |   3   |
  |   16   |                42  42 | 34, 42          |    1   |   2   |
  |   17   |                42  42 | 42              |    1   |   1   |
  |   18   |                42  42 | ...             |   ...  |  ...  |
  |        |                       |                 |        |       |
  |   19   | Ring           14  14 | 33, 42, 14      |    1   |   3   |
  |   20   |                14  14 | 42, 16          |   ...  |   2   |
  |   21   |                14  14 |  6              |   ...  |   1   |
  |   22   |                42  42 | 40              |   ...  |   1   |
  |   23   |                42  42 | 42, 42, 42      |    3   |   3   |
  |   24   |                42  42 | ...             |   ...  |  ...  |
  |   25   |                42  42 | 42, 42          |    2   |   2   |
  |   26   |                42  42 | 49, 14          |   ...  |   2   |
  |   27   |                46  46 | 48, 40, 16      |   ...  |   4   |
  |        |                       |                 |--------|-------|
  |        |                       |                 |   22   |  41   |
  |        |                       |                 |        |       |
  |        |                       |                 |        |       |
  |        |                       |                 |        |       |
  +-------------------------------------------------------------------+

  +--------------------------------------------------------------------+
  |      --of Daughters.       | Alike. |    Total   ||  Total  |Alike.|
  |                            |        | daughters. ||children.|      |
  |----------------------------|--------|------------||---------|------|
  |  1,  1                     |   2    |     2      ||    3    |   3  |
  | 42, 48                     |  ...   |     2      ||    3    |   1  |
  |  2, 40                     |   1    |     2      ||    3    |   1  |
  | 42                         |   1    |     1      ||    2    |   1  |
  |                            |        |            ||         |      |
  | 40                         |   1    |     1      ||    2    |   2  |
  | ...                        |  ...   |    ...     ||    1    |   1  |
  | 40                         |  ...   |     1      ||    2    |   1  |
  | 40,  1                     |  ...   |     2      ||    6    |   3  |
  | 40, 42                     |   1    |     2      ||    3    |   2  |
  | 42, 42, 48, 42, 42         |   4    |     5      ||    9    |   5  |
  |  1, 40                     |  ...   |     2      ||    3    |   1  |
  | 42, 42, 42, 42             |   4    |     4      ||    5    |   4  |
  | ...                        |  ...   |    ...     ||    1    |  ... |
  | 42, 42, 42                 |   3    |     3      ||    4    |   4  |
  | 42, 42, 42, 42, 42, 42, 42 |   3    |     3      ||    4    |   4  |
  | 33, 42                     |   1    |     2      ||    4    |   2  |
  | 40, 42,  1                 |   1    |     3      ||    4    |   2  |
  | 42, 42 (twins)             |   2    |     2      ||    2    |   2  |
  |                            |        |            ||         |      |
  | 32, 40                     |  ...   |     2      ||    5    |   1  |
  | 16, 14, 42, 42             |   1    |     4      ||    6    |   1  |
  |  9, 35, 48, 32, 14         |   1    |     5      ||    6    |   1  |
  | 40                         |  ...   |     1      ||    2    |  ... |
  | 40, 42                     |   1    |     2      ||    5    |   4  |
  | 40, 42                     |   1    |     2      ||    2    |   1  |
  | 42, 40, 42                 |   2    |     3      ||    5    |   4  |
  | 42, 42, 42                 |   3    |     3      ||    5    |   3  |
  | 16, 38                     |  ...   |     2      ||    6    |  ... |
  |                            |--------|------------||---------|------|
  |          Daughters         |  37    |    65      ||         |      |
  |          Sons              |  22    |    44      ||         |      |
  |                            |--------|------------||         |      |
  |          Total Children    |  59    |   109      ||   109   |  59  |
  +--------------------------------------------------------------------+

There are nineteen cases of both parents having the commonest of the loop
patterns, No. 42, on a corresponding finger. They have between them
seventy-five children, of whom forty-eight have the pattern No. 42, on the
same finger as their parents, and eighteen others have loops of other
kinds on that same finger, making a total of sixty-six coincidences out of
the possible 75, or 88 per cent, which is a great increase upon the normal
proportion of loops of the No. 42 pattern in the fore, middle, and
ring-fingers collectively. Again, there are three cases of both parents
having a tendrilled-loop No. 15, which ranks as a whorl. Out of their
total number of seventeen children, eleven have whorls and only six have
loops.

Lastly, there is a single case of both parents having an arch, and all
their three children have arches; whereas in the total of 109 children in
the table, there are only four other cases of an arch.

This partial analysis accounts for the whole of the like-patterned
parents, except four couples, which are one of No. 34, two of No. 40, and
one of No. 46. These concur in telling the same general tale, recollecting
that No. 46 might almost be reckoned as a transitional case between a loop
and a whorl.

The decided tendency to hereditary transmission cannot be gainsaid in the
face of these results, but the number of cases is too few to justify
quantitative conclusions. It is not for the present worth while to extend
them, for the reason already mentioned, namely, an ignorance of the
allowance that ought to be made for related patterns. On this account it
does not seem useful to print the results of a large amount of tabulation
bearing on the simple filial relationship between the child and either
parent separately, except so far as appears in the following paragraph.

_Relative Influence of the Father and the Mother._--Through one of those
statistical accidents which are equivalent to long runs of luck at a
gaming table, a concurrence in the figures brought out by Mr. Collins
suggested to him the existence of a decided preponderance of maternal
influence in the hereditary transmission of finger patterns. His further
inquiries have, however, cast some doubt on earlier and provisional
conclusions, and the following epitomises all of value that can as yet be
said in favour of the superiority of the maternal influence.

The fore, middle, and ring-fingers of the right hands of the father,
mother, and all their accessible children, in many families, were
severally tabulated under the fifty-three heads already specified. The
total number of children was 389, namely 136 sons and 219 daughters. The
same pattern was found on the same finger, both of a child and of one or
other of his parents, in the following number of cases:--

TABLE XXIX.

_Relative Influence of Father and Mother._

  +----------------------------------------------------------------------+
  |                     |Fore.|Middle.|Ring.|| Totals. | Corrected |     |
  |                     |     |       |     ||         |   Totals. |     |
  |---------------------|-----|-------|-----||---------|-----------|-----|
  | Father and son      | 17  |  35   | 28  ||   80    |     80    |}149 |
  |   "     "  daughter | 29  |  52   | 30  || (111)   |     69    |}    |
  |                     |     |       |     ||         |           |     |
  | Mother and son      | 18  |  50   | 26  ||   94    |     94    |}186 |
  |   "     "  daughter | 38  |  75   | 35  || (148)   |     92    |}    |
  +----------------------------------------------------------------------+

The entries in the first three columns are not comparable on equal terms,
on account of the large difference between the numbers of the sons and
daughters. This difference is easily remedied by multiplying the number of
daughters by 136/219, that is by 0·621, as has been done in the fifth
column headed Corrected Totals. It would appear from these figures, that
the maternal influence is more powerful than the paternal in the
proportion of 186 to 149, or as 5 to 4; but, as some of the details from
which the totals are built up, vary rather widely, it is better for the
present to reserve an opinion as to their trustworthiness.




CHAPTER XII

RACES AND CLASSES


The races whose finger prints I have studied in considerable numbers are
English, pure Welsh, Hebrew, and Negro; also some Basques from Cambo in
the French Pyrenees, twenty miles south-east of Bayonne. For the Welsh
prints I am primarily indebted to the very obliging help of Mr. R. W.
Atkinson, of Cardiff, who interested the masters of schools in purely
Welsh-speaking mountainous districts on my behalf; for the Hebrew prints
to Mr. Isidore Spielman, who introduced me to the great Hebrew schools in
London, whose head-masters gave cordial assistance; and for the Negro
prints to Sir George Taubman Goldie, Dep. Governor of the Royal Niger Co.,
who interested Dr Crosse on my behalf, from whom valuable sets of prints
were received, together with particulars of the races of the men from whom
they were made. As to the Basques, they were printed by myself.

It requires considerable patience and caution to arrive at trustworthy
conclusions, but it may emphatically be said that there is no _peculiar_
pattern which characterises persons of any of the above races. There is
no particular pattern that is special to any one of them, which when met
with enables us to assert, or even to suspect, the nationality of the
person on whom it appeared. The only differences so far observed, are
statistical, and cannot be determined except through patience and caution,
and by discussing large groups.

I was misled at first by some accidental observations, and as it seemed
reasonable to expect to find racial differences in finger marks, the
inquiries were continued in varied ways until hard fact had made hope no
longer justifiable.

After preliminary study, I handed over the collection of racial finger
prints to Mr F. Howard Collins, who kindly undertook the labour of
tabulating them in many ways, of which it will be only necessary to give
an example. Thus, at one time attention was concentrated on a single
finger and a single pattern, the most instructive instance being that of
arches on the right fore-finger. They admit of being defined with
sufficient clearness, having only one doubtful frontier of much
importance, namely that at which they begin to break away into
nascent-loops, etc. They also occur with considerable frequency on the
fore-finger, so the results from a few hundred specimens ought to be
fairly trustworthy. It mattered little in the inquiry, at what level the
limit was drawn to separate arches from nascent-loops, so long as the same
limit was observed in all races alike. Much pains were taken to secure
uniformity of treatment, and Mr. Collins selected two limits, the one
based on a strict and the other on a somewhat less strict interpretation
of the term "arches," but the latter was not so liberal as that which I
had used myself in the earlier inquiries (see p. 114). His results showed
no great difference in the proportionate frequency of arches in the
different races, whichever limit was observed; the following table refers
to the more liberal limit:--

TABLE XXX.

_Frequency of Arches in the Right Fore-Finger._

  +--------------------------------------------------------------------+
  |  No. of  |             Race.                |  No. of | Per Cents. |
  | Persons. |                                  | Arches. |            |
  |----------|----------------------------------|---------|------------|
  |    250   | English                          |    34   |   13·6     |
  |    250   | Welsh                            |    26   |   10·8     |
  |   1332   | Hebrew                           |   105   |    7·9     |
  |    250   | Negro                            |    27   |   11·3     |
  |          |                                  |         |            |
  |          |       _Hebrews in detail_--      |         |            |
  |    500   | Boys, Bell Lane School           |    35   |    7·0     |
  |    400   | Girls, Bell Lane School          |    34   |    8·5     |
  |    220   | Boys, Tavistock St. & Hanway St. |    18   |    8·2     |
  |    212   | Girls, Hanway Street School      |    18   |    8·5     |
  +--------------------------------------------------------------------+

The two contrasted values here are the English and the Hebrew. The 1332
cases of the latter give a percentage result of 7·9, which differs as may
be seen less than 1 per cent from that of any one of the four large groups
upon which the average is based. The 250 cases of English are
comparatively few, but the experience I have had of other English prints
is so large as to enable me to say confidently that the percentage result
of 13·6 is not too great. It follows, that the percentage of arches in the
English and in the Hebrew differs in the ratio of 13·6 to 7·9, or nearly
as 5 to 3. This is the largest statistical difference yet met with. The
deficiency in arches among the Hebrews, and to some extent in loops also,
is made up by a superiority in whorls, chiefly of the tendril or
circlet-in-loop patterns.

It would be very rash to suppose that this relative infrequency of arches
among the Hebrews was of fundamental importance, considering that such
totally distinct races as the Welsh and the Negro have them in an
intermediate proportion. Still, why does it occur? The only answer I can
suggest is that the patterns being in some degree hereditary, such
accidental preponderances as may have existed among a not very numerous
ancestry might be perpetuated. I have some reason to believe that local
peculiarities of this sort exist in England, the children in schools of
some localities seeming to be statistically more alike in their patterns
than English children generally.

Another of the many experiments was the tabulation separately by Mr.
Collins of the fore, middle, and ring-fingers of the right hand of fifty
persons of each of the five races above-mentioned: English, Welsh, Basque,
Hebrew, and different groups of Negroes. The number of instances is of
course too small for statistical deductions, but they served to make it
clear that no very marked characteristic distinguished the races. The
impressions from Negroes betray the general clumsiness of their fingers,
but their patterns are not, so far as I can find, different from those of
others, they are not simpler as judged either by their contours or by the
number of origins, embranchments, islands, and enclosures contained in
them. Still, whether it be from pure fancy on my part, or from the way in
which they were printed, or from some real peculiarity, the general aspect
of the Negro print strikes me as characteristic. The width of the ridges
seems more uniform, their intervals more regular, and their courses more
parallel than with us. In short, they give an idea of greater simplicity,
due to causes that I have not yet succeeded in submitting to the test of
measurement.

The above are only a few examples of the laborious work so kindly
undertaken for me by Mr. F. H. Collins, but it would serve no useful
purpose to give more in this book, as no positive results have as yet been
derived from it other than the little already mentioned.

The most hopeful direction in which this inquiry admits of being pursued
is among the Hill tribes of India, Australian blacks, and other diverse
and so-called aboriginal races. The field of ethnology is large, and it
would be unwise as yet to neglect the chance of somewhere finding
characteristic patterns.

       *       *       *       *       *

Differences between finger prints of different classes might continue to
exist although those of different races are inconspicuous, because every
race contains men of various temperaments and faculties, and we cannot
tell, except by observation, whether any of these are correlated with the
finger marks. Several different classes have been examined both by Mr.
Collins and myself. The ordinary laboratory work supplies finger prints of
persons of much culture, and of many students both in the Art and in the
Science schools. I took a large number of prints from the worst idiots in
the London district, through the obliging assistance of Dr. Fletcher
Beech, of the Darenth Asylum; my collections made at Board Schools are
numerous, and I have one of field labourers in Dorsetshire and
Somersetshire. But there is no notable difference in any of them. For
example; the measurements of the ridge-interval gave the same results in
the art-students and in the science-students, and I have prints of eminent
thinkers and of eminent statesmen that can be matched by those of
congenital idiots.[5] No indications of temperament, character, or ability
are to be found in finger marks, so far as I have been able to discover.

Of course these conclusions must not be applied to the general shape of
the hand, which as yet I have not studied, but which seems to offer a very
interesting field for exact inquiry.




CHAPTER XIII

GENERA


The same familiar patterns recur in every large collection of finger
prints, and the eye soon selects what appear to be typical forms; but are
they truly "typical" or not? By a type I understand an ideal form around
which the actual forms are grouped, very closely in its immediate
neighbourhood, and becoming more rare with increasing rapidity at an
increasing distance from it, just as is the case with shot marks to the
right or left of a line drawn vertically through the bull's eye of a
target. The analogy is exact; in both cases there is a well-defined point
of departure; in both cases the departure of individual instances from
that point is due to a multitude of independently variable causes. In
short, both are realisations of the now well-known theoretical law of
Frequency of Error. The problem then is this:--take some one of the
well-marked patterns, such as it appears on a particular digit,--say a
loop on the right thumb; find the average number of ridges that cross a
specified portion of it; then this average value will determine an ideal
centre from which individual departures may be measured; next, tabulate
the frequency of the departures that attain to each of many successive
specified distances from that ideal centre; then see whether their
diminishing frequency as the distances increase, is or is not in
accordance with the law of frequency of error. If it is, then the central
form has the attributes of a true type, and such will be shown to be the
case with the loops of either thumb. I shall only give the data and the
results, not the precise way in which they are worked out, because an
account of the method employed in similar cases will be found in _Natural
Inheritance_, and again in the Memoir on Finger Prints in the _Phil.
Trans._; it is too technical to be appropriate here, and would occupy too
much space. The only point which need be briefly explained and of which
non-mathematical readers might be ignorant, is how a single numerical
table derived from abstract calculations can be made to apply to such
minute objects as finger prints, as well as to the shot marks on a huge
target; what is the common unit by which departures on such different
scales are measured? The answer is that it is a self-contained unit
appropriate to _each series severally_, and technically called the
Probable Error, or more briefly, P.E., in the headings to the following
tables. In order to determine it, the range of the central half of the
series has to be measured, namely, of that part of the series which
remains after its two extreme quarters have been cut off and removed. The
series had no limitation before, its two ends tailing away indefinitely
into nothingness, but, by the artifice of lopping off a definite fraction
of the whole series from both ends of it, a sharply-defined length, call
it PQ, is obtained. Such series as have usually to be dealt with are
fairly symmetrical, so the position of the half-way point M, between P and
Q, corresponds with rough accuracy to the average of the positions of all
the members of the series, that is to the point whence departures have to
be measured. MP, or MQ,--or still better, 1/2(MP + MQ) is the
above-mentioned Probable Error. It is so called because the amount of
Error, or Departure from M of any one observation, falls just as often
within the distance PE as it falls without it. In the calculated tables of
the Law of Frequency, PE (or a multiple of it) is taken as unity. In each
observed series, the actual measures have to be converted into another
scale, in which the PE of that series is taken as unity. Then observation
and calculation may be compared on equal terms.


[Illustration]


Observations were made on the loops of the right and left thumbs
respectively. AHB is taken as the primary line of reference in the loop;
it is the line that, coinciding with the axis of the _uppermost portion_,
and that only, of the core, cuts the summit of the core at H, the upper
outline at A, and the lower outline, if it cuts it at all, as it nearly
always does, at B. K is the centre of the single triangular plot that
appears in the loop, which may be either I or O. KNL is a perpendicular
from K to the axis, cutting it at N, and the outline beyond at L. In some
loops N will lie above H, as in Plate 4, Fig. 8; in some it may coincide
with H. (See Plate 6 for numerous varieties of loop.) These points were
pricked in each print with a fine needle; the print was then turned face
downwards and careful measurements made between the prick holes at the
back. Also the number of ridges in AH were counted, the ridge at A being
reckoned as 0, the next ridge as 1, and so on up to H. Whenever the line
AH passed across the neck of a bifurcation, there was necessarily a single
ridge on one side of the point of intersection and two ridges on the
other, so there would clearly be doubt whether to reckon the neck as one
or as two ridges. A compromise was made by counting it as 1-1/2. After the
number of ridges in AH had been counted in each case, any residual
fractions of 1/2 were alternately treated as 0 and as 1. Finally, six
series were obtained; three for the right thumb, and three for the left.
They referred respectively (1) to the Number of Ridges in AH; (2) to
KL/NB; (3) to AN/AH, all the three being independent of stature. The
number of measures in each of the six series varied from 140 to 176; they
are reduced to percentages in Table XXXI.

We see at a glance that the different numbers of ridges in AH do not occur
with equal frequency, that a single ridge in the thumb is a rarity, and so
are cases above fifteen in number, but those of seven, eight, and nine
are frequent. There is clearly a rude order in their distribution, the
number of cases tailing away into nothingness, at the top and bottom of
the column. A vast amount of statistical analogy assures us that the
orderliness of the distribution would be increased if many more cases had
been observed, and later on, this inference will be confirmed. There is a
sharp inferior limit to the numbers of ridges, because they cannot be less
than 0, but independently of this, we notice the infrequency of small
numbers as well as of large ones. There is no strict limit to the latter,
but the trend of the entries shows that forty, say, or more ridges in AH
are practically impossible. Therefore, in no individual case can the
number of ridges in AH depart very widely from seven, eight, or nine,
though the range of possible departures is not sharply defined, except at
the lower limit of 0. The range of variation is _not_ "rounded off," to
use a common but very inaccurate expression often applied to the way in
which genera are isolated. The range of possible departures is not defined
by any rigid boundary, but the rarity of the stragglers rapidly increases
with the distance at which they are found, until no more of them are met
with.

The values of KL/NB and of AN/AH run in a less orderly sequence, but
concur distinctly in telling a similar tale. Considering the paucity of
the observations, there is nothing in these results to contradict the
expectation of increased regularity, should a large addition be made to
their number.

TABLE XXXI.

  +---------------------------------------------------------------------+
  |      | No. of cases ||       | No. of cases ||       | No. of cases |
  |      |   reduced    ||       |   reduced    ||       |   reduced    |
  |No. of| to per cents.||   KL  | to per cents.||   AN  | to per cents.|
  |ridges|--------------||   --  |--------------||   --  |--------------|
  |in AH.| Right.| Left.||   NB  | Right.| Left.||   AH  | Right.| Left.|
  |      |-------|------||       |-------|------||       |-------|------|
  |      |  171  |  166 ||       |  149  |  140 ||       |  176  |  163 |
  |      | cases.| cases||       | cases.| cases||       | cases | cases|
  |------|-------|------||-------|-------|------||-------|-------|------|
  |   1  |    1  |  ... ||0·3-0·4|    3  |    2 ||0·1-0·2|    2  |    1 |
  |   2  |    2  |    1 ||0·5-0·6|    8  |   11 ||0·3-0·4|    7  |    3 |
  |   3  |    2  |    3 ||0·7-0·8|    9  |   14 ||0·5-0·6|   11  |    3 |
  |   4  |    2  |    5 ||0·9-1·0|   21  |   18 ||0·7-0·8|    9  |    9 |
  |   5  |    3  |    5 ||1·1-1·2|   16  |   23 ||0·9-1·0|   22  |   15 |
  |   6  |    4  |   18 ||1·3-1·4|   24  |    7 ||1·1-1·2|   15  |   13 |
  |   7  |    8  |   14 ||1·5-1·6|    8  |   10 ||1·3-1·4|   12  |   12 |
  |   8  |    8  |   16 ||1·7-1·8|    3  |    6 ||1·5-1·6|   11  |   14 |
  |   9  |   11  |   10 ||1·9-2·0|    5  |    6 ||1·7-1·8|    8  |   10 |
  |  10  |    9  |    8 ||2·1-2·2|    1  |    1 ||1·9-2·0|    1  |    5 |
  |  11  |   14  |   10 || above |    2  |    2 ||2·1-2·2|  ...  |  ... |
  |  12  |   11  |    8 ||  ...  |  ...  |  ... ||2·3-2·4|    1  |    6 |
  |  13  |   10  |    2 ||  ...  |  ...  |  ... ||2·5-2·6|  ...  |    4 |
  |  14  |    7  |  ... ||  ...  |  ...  |  ... ||2·7-2·8|  ...  |    3 |
  |  15  |    6  |  ... ||  ...  |  ...  |  ... ||2·9-3·0|  ...  |    1 |
  |above |    2  |  ... ||  ...  |  ...  |  ... || above |    1  |    1 |
  |      |-------|------||       |-------|------||       |-------|------|
  |      |  100  |  100 ||       |  100  |  100 ||       |  100  |  100 |
  +---------------------------------------------------------------------+

TABLE XXXII.

  +---------------------------------------------+
  |           |Ordinates to the six schemes of  |
  |           |Distribution, being the ordinates|
  |           |drawn from the base of each      |
  |           |scheme at selected centesimal    |
  |           |divisions of the base.           |
  | Abscissae |---------------------------------|
  | reckoned  |                                 |
  | in        |     No. of ridges in AH.        |
  | centesimal|                                 |
  | parts of  |---------------------------------|
  | the       |     Right.     |     Left.      |
  | interval  |----------------|----------------|
  | between   |  O  |Calculated|  O  |Calculated|
  | the limits|  b  |from      |  b  |from      |
  | of the    |  s  |M=10·4    |  s  |M=7·8     |
  | scheme.   |  e  |p.e.=2·3  |  e  |p.e.=1·9  |
  | 0° to     |  r  |          |  r  |          |
  | 100°.     |  v  |          |  v  |          |
  |           |  e  |          |  e  |          |
  |           |  d  |          |  d  |          |
  |-----------|-----|----------|-----|----------|
  |   5       | 3·8 |    4·8   | 3·8 |   3·2    |
  |     10    | 5·5 |    6·0   | 4·8 |   4·2    |
  |     20    | 7·3 |    7·5   | 5·8 |   5·4    |
  |  25       | 7·9 |    8·1   | 6·1 |   5·9    |
  |     30    | 8·5 |    8·6   | 6·4 |   6·3    |
  |     40    | 9·5 |    9·5   | 7·1 |   7·4    |
  |     50    |10·5 |   10·4   | 7·8 |   7·8    |
  |     60    |11·3 |   11·3   | 8·4 |   8·2    |
  |     70    |12·1 |   12·2   | 9·3 |   9·3    |
  |  75       |12·5 |   12·7   | 9·9 |   9·7    |
  |     80    |13·0 |   13·3   |11·0 |  10·2    |
  |     90    |14·3 |   14·8   |11·5 |  11·4    |
  |  95       |15·0 |   16·0   |12·2 |  12·2    |
  +---------------------------------------------+

  +---------------------------------------------------------------------+
  |                   KL            ||                  AN              |
  |         Values of --            ||        Values of --              |
  |                   NB            ||                  AH              |
  |---------------------------------||----------------------------------|
  |     Right.     |     Left.      ||     Right.     |     Left.       |
  |----------------|----------------||----------------|-----------------|
  |  O  |Calculated|  O  |Calculated||  O  |Calculated|  O  |Calculated |
  |  b  |from      |  b  |from      ||  b  |from      |  b  |from       |
  |  s  |M=1·15    |  s  |M=1·10    ||  s  |M=1·08    |  s  |M=1·36     |
  |  e  |p.e.=0·25 |  e  |p.e.=0·31 ||  e  |p.e.=0·30 |  e  |p.e.=0·36  |
  |  r  |          |  r  |          ||  r  |          |  r  |           |
  |  v  |          |  v  |          ||  v  |          |  v  |           |
  |  e  |          |  e  |          ||  e  |          |  e  |           |
  |  d  |          |  d  |          ||  d  |          |  d  |           |
  |-----|----------|-----|----------||-----|----------|-----|-----------|
  |0·54 |   0·54   |0·49 |   0·35   ||0·36 |  0·32    |0·58 |   0·48    |
  |0·64 |   0·67   |0·59 |   0·51   ||0·50 |  0·48    |0·74 |   0·68    |
  |0·85 |   0·84   |0·78 |   0·71   ||0·66 |  0·67    |0·96 |   0·91    |
  |0·91 |   0·90   |0·83 |   0·79   ||0·79 |  0·75    |1·00 |   l·00    |
  |0·99 |   0·95   |0·89 |   0·86   ||0·87 |  0·82    |1·04 |   1·08    |
  |1·05 |   1·05   |1·00 |   0·98   ||0·98 |  0·93    |1·21 |   1·22    |
  |1·15 |   1·15   |1·10 |   1·10   ||1·04 |  1·05    |1·37 |   1·36    |
  |1·29 |   1·25   |1·18 |   1·22   ||1·18 |  1·17    |1·48 |   1·50    |
  |1·33 |   1·35   |1·32 |   1·34   ||1·31 |  1·28    |1·66 |   1·64    |
  |1·41 |   1·40   |1·46 |   1·41   ||1·39 |  1·35    |1·73 |   1·72    |
  |1·45 |   1·46   |1·53 |   1·49   ||1·48 |  1·43    |1·90 |   2·81    |
  |1·77 |   1·63   |1·73 |   1·69   ||1·69 |  1·62    |2·23 |   2·04    |
  |2·00 |   1·76   |1·80 |   1·85   ||1·81 |  1·78    |2·48 |   2·24    |
  +---------------------------------------------------------------------+

TABLE XXXIII.

  +-------------------------------------------------------
  |            | Ordinates to the six curves of          |
  |            | distribution, drawn from the axis of    |
  |            | each curve at selected centesimal       |
  |            | divisions of it.                        |
  |            |                                         |
  |            | They are here reduced to a common       |
  |            | measure, by dividing the observed       |
  |            | deviations in each series by the        |
  |Abscissae   | probable error appropriate to the       |
  |reckoned in | series, and multiplying by 100. For the |
  |centesimal  | values of M, whence the deviations are  |
  |parts of the| measured, and for those of the          |
  |interval    | corresponding probable error, see the   |
  |between the | headings to the columns in Table II.    |
  |limits of   |-----------------------------------------|
  |the curve.  |    No. of   |          KL |          AN |
  |0° to 100°. |    Ridges   |Values of -- |Values of -- |
  |            |    in AH.   |          NB |          AH |
  |            |-------------|-------------|-------------|
  |            |Right.| Left.|Right.| Left.|Right.| Left.|
  |------------|------|------|------|------|-------------|
  |     5      | -291 | -211 | -244 | -196 | -230 | -217 |
  |         10 | -213 | -158 | -204 | -164 | -183 | -172 |
  |         20 | -135 | -105 | -120 | -103 | -130 | -111 |
  |(P) 25      | -109 | - 84 | - 92 | - 87 | - 87 | -100 |
  |         30 | - 83 | - 74 | - 64 | - 68 | - 60 | - 89 |
  |         40 | - 44 | - 37 | - 44 | - 31 | - 23 | - 42 |
  |(M) 50      | +  4 |    0 |    0 |    0 |    0 |    0 |
  |         60 | + 39 | + 31 | + 56 | + 23 | + 43 | + 33 |
  |         70 | + 74 | + 79 | + 72 | + 68 | + 87 | + 83 |
  |(Q) 75      | + 91 | +116 | +104 | +116 | +113 | +103 |
  |         80 | +113 | +168 | +120 | +138 | +143 | +150 |
  |         90 | +170 | +200 | +248 | +203 | +213 | +242 |
  |    95      | +200 | +231 | +340 | +225 | +253 | +311 |
  +-------------------------------------------------------

  -------------------------------------+
  |                  |                 |
  |     Observed.    |   Calculated.   |
  |------------------|-----------------|
  |   Mean of the    |                 |
  |  corresponding   |                 |
  |   ordinates in   |                 |
  |  the six curves  |                 |
  |  after reduction |                 |
  |   to the common  |   Ordinates to  |
  |     scale of     | the normal curve|
  |   p.e. = 100.    | of distribution,|
  | 965 observations | probable error  |
  |     in all.      |      = 100.     |
  |------------------|-----------------|
  |      -231        |       -244      |
  |      -182        |       -190      |
  |      -117        |       -125      |
  |      - 93        |       -100      |
  |      - 73        |       - 78      |
  |      - 37        |       - 38      |
  |      +  1        |          0      |
  |      + 38        |       + 38      |
  |      + 77        |       + 78      |
  |      +107        |       +100      |
  |      +139        |       +125      |
  |      +213        |       +190      |
  |      +260        |       +244      |
  -------------------------------------+

Table XXXII. is derived from Table XXXI. by a process described by myself
in many publications, more especially in _Natural Inheritance_, and will
now be assumed as understood. Each of the six pairs of columns contain,
side by side, the Observed and Calculated values of one of the six series,
the data on which the calculations were made being also entered at the
top. The calculated figures agree with the observed ones very respectably
throughout, as can be judged even by those who are ignorant of the
principles of the method. Let us take the value that 10 per cent of each
of the six series falls short of, and 90 per cent exceed; they are entered
in the line opposite 10; we find for the six pairs successively,

  _Obs._:  5·5   4·8   0·64   0·59   0·50   0·74

  _Calc._: 6·0   4·2   0·67   0·51   0·48   0·68

The correspondence between the more mediocre cases is much closer than
these, and very much closer than between the extreme cases given in the
table, namely, the values that 5 per cent fall short of, and 95 exceed.
These are of course less regular, the observed instances being very few;
but even here the observations are found to agree respectably well with
the proportions given by calculation, which is necessarily based upon the
supposition of an infinite number of cases having been included in the
series.

As the want of agreement between calculation and observation must be
caused in part by the paucity of observations, it is worth while to make
a larger group, by throwing the six series together, as in Table XXXIII.,
making a grand total of 965 observations. Their value is not so great as
if they were observations taken from that number of different persons,
still they are equivalent to a large increase of those already discussed.
The six series of observed values were made comparable on equal terms by
first reducing them to a uniform PE and then by assigning to M, the point
of departure, the value of 0. The results are given in the last column but
one, where the orderly run of the observed data is much more conspicuous
than it was before. Though there is an obvious want of exact symmetry in
the observed values, their general accord with those of the calculated
values is very fair. It is quite close enough to establish the general
proposition, that we are justified in the conception of a typical form of
loop, different for the two thumbs; the departure from the typical form
being usually small, sometimes rather greater, and rarely greater still.

I do not see my way to discuss the variations of the arches, because they
possess no distinct points of reference. But their general appearance does
not give the impression of clustering around a typical centre. They
suggest the idea of a fountain-head, whose stream begins to broaden out
from the first.

As regards other patterns, I have made many measurements altogether, but
the specimens of each sort were comparatively few, except in whorled
patterns. In all cases where I was able to form a well-founded opinion,
the existence of a typical centre was indicated.

It would be tedious to enumerate the many different trials made for my own
satisfaction, to gain assurance that the variability of the several
patterns is really of the quasi-normal kind just described. In the first
trial I measured in various ways the dimensions of about 500 enlarged
photographs of loops, and about as many of other patterns, and found that
the measurements in each and every case formed a quasi-normal series. I do
not care to submit these results, because they necessitate more
explanation and analysis than the interest of the corrected results would
perhaps justify, to eliminate from them the effect of variety of size of
thumb, and some other uncertainties. Those measurements referred to some
children, a few women, many youths, and a fair number of adults; and
allowance has to be made for variability in stature in each of these
classes.

The proportions of a typical loop on the thumb are easily ascertained if
we may assume that the most frequent values of its variable elements,
taken separately, are the same as those that enter into the most frequent
combination of the elements taken collectively. This would necessarily be
true if the variability of each element separately, and that of the sum of
them in combination, were all strictly normal, but as they are only
quasi-normal, the assumption must be tested. I have done so by making the
comparisons (_A_) and (_B_) shown in Table XXXIV., which come out
correctly to within the first decimal place.

TABLE XXXIV.

  +------------------------------------------------------+
  |                                        |Right | Left |
  |                                        |Thumb.|Thumb.|
  |----------------------------------------|------|------|
  |(_a_)  Median of all the values of KL   | 12·5 | 10·1 |
  |(_b_)  Median of all the values of NB   | 10·1 |  8·9 |
  |                                        |------|------|
  |(_A_)  Value of _a/b_                   |  1·24|  1·11|
  |(_A_)  Median of all the fractions KL/NB|  1·15|  1·10|
  |========================================|======|======|
  |(_c_)  Median of all the values of AN   |  4·6 |  4·6 |
  |(_d_)  Median of all the values of AH   |  4·4 |  3·3 |
  |                                        |------|------|
  |(_B_)  Value of _c/d_                   |  1·05|  1·40|
  |(_B_)  Median of all the fractions AN/AH|  1·08|  1·36|
  +------------------------------------------------------+

It has been shown that the patterns are hereditary, and we have seen that
they are uncorrelated with race or temperament or any other noticeable
peculiarity, inasmuch as groups of very different classes are alike in
their finger marks. They cannot exercise the slightest influence on
marriage selection, the very existence both of the ridges and of the
patterns having been almost overlooked; they are too small to attract
attention, or to be thought worthy of notice. We therefore possess a
perfect instance of promiscuity in marriage, or, as it is now called,
panmixia, in respect to these patterns. We might consequently have
expected them to be hybridised. But that is not the case; they _refuse to
blend_. Their classes are as clearly separated as those of any of the
genera of plants and animals. They keep pure and distinct, as if they had
severally descended from a thorough-bred ancestry, each in respect to its
own peculiar character.

As regards other forms of natural selection, we know that races are kept
pure by the much more frequent destruction of those individuals who depart
the more widely from the typical centre. But natural selection was shown
to be inoperative in respect to individual varieties of patterns, and
unable to exercise the slightest check upon their vagaries. Yet, for all
that, the loops and other classes of patterns are isolated from one
another just as thoroughly and just in the same way as are the genera or
species of plants and animals. There is no statistical difference between
the form of the law of distribution of individual Loops about their
respective typical centres, and that of the law by which, say, the Shrimps
described in Mr. Weldon's recent memoirs (_Proc. Roy. Soc._, 1891 and
1892) are distributed about theirs. In both cases the distribution is in
quasi-accordance with the theoretical law of Frequency of Error, this form
of distribution being entirely caused in the patterns, by _internal_
conditions, and in no way by natural selection in the ordinary sense of
that term.

It is impossible not to recognise the fact so clearly illustrated by these
patterns in the thumbs, that natural selection has no monopoly of
influence in the construction of genera, but that it could be wholly
dispensed with, the internal conditions acting by themselves being
sufficient. When the internal conditions are in harmony with the external
ones, as they appear to be in all long-established races, their joint
effects will curb individual variability more tightly than either could do
by itself. The normal character of the distribution about the typical
centre will not be thereby interfered with. The probable divergence (=
probable error) of an individual taken at random, will be lessened, and
that is all.

Not only is it impossible to substantiate a claim for natural selection,
that it is the sole agent in forming genera, but it seems, from the
experience of artificial selection, that it is scarcely competent to do so
by favouring mere _varieties_, in the sense in which I understand the
term.

My contention is that it acts by favouring small _sports_. Mere varieties
from a common typical centre blend freely in the offspring, and the
offspring of every race whose _statistical_ characters are constant,
necessarily tend, as I have often shown, to regress towards their common
typical centre. Sports, on the other hand, do not blend freely; they are
fresh typical centres or sub-species, which suddenly arise we do not yet
know precisely through what uncommon concurrence of circumstance, and
which observations show to be strongly transmissible by inheritance.

A mere variety can never establish a sticking-point in the forward course
of evolution, but each new sport affords one. A substantial change of type
is effected, as I conceive, by a succession of small changes of typical
centre, each more or less stable, and each being in its turn favoured and
established by natural selection, to the exclusion of its competitors. The
distinction between a mere variety and a sport is real and fundamental. I
argued this point in _Natural Inheritance_, but had then to draw my
illustrations from non-physiological experiences, no appropriate
physiological ones being then at hand: this want is now excellently
supplied by observations of the patterns on the digits.




INDEX


  AH, number of ridges in, 200

  Allix, 60

  A. L. W. system, 80

  Ambiguities in minutiæ, 91, 111

  America, 163

  Anthropometric laboratory, 4, 35

  Arches, 7, 75, 78;
    interpretations of, 114, 193

  Artisans, 59

  Artists, 58

  Assyrian bricks, 25

  Atkinson, R. F., 192

  Author, the, finger prints of, 8, 58, 73

  Axis of pattern, 68


  Ball for inking, 42

  Ball of thumb, 96

  Basques, 18, 192

  Bearings as by compass, 84

  Beech, Dr. Fletcher, 197

  Benzole, 36, 41

  Bertillon, 2, 15, 154, 169;
    _Bertillonage_, 155, 164, 167

  Bewick, 26

  Bible, the, 22

  Bifurcations, 91

  Binomial law, 11, 112

  Bird's nest, 34

  Blacklead, 49

  Blood as ink, 45

  Bowditch, H. P., Professor, 47

  British Museum, 25

  Brobdingnags, 1

  Brothers, 171

  Burns of finger, 59


  C. set of standard patterns, 177

  Callosities, 59

  Cambo, 18, 192

  Camera lucida, 52, 104

  Cards, 38;
    keeping in order, 145

  Casts, 49

  Centesimal scale, 12, 17, 124, 129, 182

  Cheiromancy, 1, 26;
    creases, 56

  Chequer-work, 106

  Chess board, 106

  Chinese deed, 24;
    money, 25;
    cheiromancy, 26;
    registration of Chinese, 26, 152

  Cicatrix, 59

  Circular patterns, optical illusion, 77

  Collins, F. H., 17, 21, 177, 190, 193

  Collodion, 51

  Colour-blindness, 71

  Comparison of prints, 90, 167

  Compass bearings, 84

  Compasses, test by the points of, 61

  Copper sheeting for inking, 42;
    for smoking, 48

  Cores, 6, 76, 145

  Correlation, 158

  Couplets of digits, 119;
    of A and B brothers, 172

  Creases, 1, 56;
    in infant, 57

  Criminals, 149

  Crosse, Dr., 192

  Cylinder, revolving, 49


  Dabs by the finger, 40, 90, 153

  Darenth Asylum, 19, 197

  Demography, Congress of, 163

  Deserters, 149, 164

  Development, 58

  Digits, peculiarities of, 114

  Direction of twist, 78

  Divergence of ridges, 68

  Drawing master, 48

  Ducts, 57

  Dyes, 44


  Ear-marking the A, B sets of brothers, 172

  Embryology, 58

  Enclosures within ridges, 92

  English, the, 17, 192

  Enlargements, 51

  Envelopes to rods or staples, 76

  Error, law of, 19, 198;
    "probable," 199

  EVIDENTIAL VALUE, Chap. VII., 100

  Evolution, 20, 60

  Eyes in patterns, 143


  Fauld, Mr., 26

  Feet, prints of, 45;
    ridges on, 57, 58

  Féré, M., 197

  Ferris, Major, 149

  Ferro-prussiate process, 51, 53, 90

  File, 63

  Flexure, lines of, in palm, 56

  Focus of eye, range of, 72

  Folders;--inked, 42;
    smoked, 48

  Foot-paths, 107

  Forgeot, Dr., 46

  Forks, 91

  Fraternity, 16, 171

  Frequency of error, law of, 19, 198

  Funnel, 36

  Furrows, not followed, 82


  G----, Sir W., 89, 97

  GENERA, Chap. XIII., 198;
    the nine chief genera, 6, 80

  Glass, temporary prints on, 30;
    etched, 47;
    for lantern, 51

  Glue, 48

  Goldie, Sir G. T., 192

  Granulations on rollers, 34

  Greenleaf, Col. C. R., 164

  Gulliver, 1

  Gum, 48

  Gutta-percha, 50


  Hand, 23, 45

  Harrild, Messrs., 36, 41

  Hawksley, 42

  Haycraft, Dr. J. B., 51

  Head-length and breadth, 158

  Hebrews, 18, 192, 194

  Herbette, M., 168

  HEREDITY, Chap. XI., 170;
    _see also_ 16

  Herschel, Sir W. J., 4, 9, 27;
    instructions for printing, 45;
    data for persistence, 89;
    right fore-finger of, 95;
    official experience, 27, 149, 153

  Hindoos, 152


  I (or Inner side), 70

  Identification, 147;
    _see_ Jezebel, 113

  Idiots, 8, 19, 59, 197

  Illusion, 66, 77

  Indexing, power of, 14, 139, 167;
    methods of, 131;
    specimen of, 133;
    search in, 166

  India-rubber for roller, 40

  Ink, printer's, 37;
    for stamp, 45

  Inner side, 70

  Interpolation of ridges, 102, 104

  Interspace, 54, 67

  Interval, equally discernible, 65, 101

  Islands, 92


  Japan, 23, 26

  Jews, 18, 192, 194

  Jezebel, 113


  Kensington, S., my laboratory at, 4, 35

  Klaatsch, Dr. H., 60

  Kollmann, Dr. A., 58


  Labels, gummed, as for luggage, 48

  Laboratory, anthropometric, 4, 35

  Labourers, 59, 197

  Lace, 9, 98

  Ladies' hands, ridges on, 32

  Language, inadequacy of, 172

  Lankester, Prof. Ray, 45

  Left and right, 70

  Lenses, 72

  Letters, alike when reversed, 71

  Licked paper, 48

  Linen-tester (lens), 73

  Linseed oil, 37

  Litharge, 35

  Lithography, 43

  Loops, 7, 75, 78;
    predominance of, 101;
    relationships of, 184;
    on thumbs, 200;
    typical shape of, 207

  Lying Bob, 27

  Lyon, 155


  Mammalia, 60

  Marseille, 155

  Measurement of patterns, 82

  Memoirs by the author, 3

  METHODS OF INDEXING, Chap. IX., 131

  METHODS OF PRINTING, Chap. III., 30

  Mica, 47, 51

  Minutiæ, 54;
    ambiguities in, 91, 99

  Monkey pattern, 18, 54, 77;
    ridges on tail, 60;
    Purkenje on, 86, 88;
    stuffed, 97

  Morgue, 148;
    _see_ Jezebel, 113

  Mould for casting rollers, 40

  Mountain ranges, 32

  Mucilage, 48

  Mummies, ridges still visible, 97


  Nail-marks, 25, 67

  Natural selection, 20, 210

  Negro, 18, 192, 195;
    cheiromancy, 26

  Ngeu-yang-siun, 25

  Notes, musical, 63


  Oil, oxidisation of, 34, 43;
    for ink, 37

  Orientation, 68

  Outer side, 70

  Outlines, 6, 69;
    followed with a point, 74

  Overtones, 63


  Pacinian bodies, 60

  Pad for stamp, 32, 44;
    of paper, 38

  Palm of the hand, 54, 88, 113

  Palmistry, 1, 26;
    _see_ Cheiromancy, 56

  Panmixia, 20, 209

  Pantagraph, 52

  Paper in pads, 38;
    _see_ Cards

  Papillæ, 60

  Paraffin, 36

  Paris, 155

  Passports, 15, 149

  Paste, 48

  PATTERNS: THEIR OUTLINES AND CORES, Chap. V., 64;
    _see also_ 2, 54, 170;
    number of easily distinguishable patterns, 100;
    standard, 74, 80;
    ditto C. set, 177;
    percentage frequency of, 115

  PECULIARITIES OF THE DIGITS, Chap. VIII., 114

  PERSISTENCE, Chap. VI., 89

  PERSONAL IDENTIFICATION, Chap. X., 147;
    _see also_ 16, 113;
    lecture on, 2

  Photographers, 147;
    photographs, 3, 51

  Plots, triangular, 67, 82

  Plumbago, 49

  Pocket printing apparatus, 40

  Points of reference, 90

  Poole, Mr. S. L., 25

  Pores, 57

  PREVIOUS USE OF FINGER PRINTS, Chap. II., 22

  Printing, the methods of, 30;
    printer's ink, 35

  Prism, 52, 104

  Purkenje's _Commentatio_, 84;
    _see also_ 8, 64, 67;
    on slope of loop, 119


  RACES AND CLASSES, Chap. XII., 192;
    _see also_ 17

  Radial, 70

  Random events, 172;
    _see also_ 126

  Razor, prints on, 30

  Reconstruction of hidden ridges, 102

  Reeves and Co., 35

  Registration in India, 28, 151

  Regression, 21, 171

  Relationship in fingers, 12, 123;
    fraternal, 171, 175;
    in twins, 185;
    filial, 190;
    ditto of like-patterned parents, 187;
    in patterns, 178;
    paternal and maternal, 190

  Reticulation, 108

  Reversals, 43, 71

  RIDGES AND THEIR USES, Chap. IV., 54;
    _see also_ low relief of ridges, 32;
    counting them, 73;
    ridge-interval, 62:--measurement by, 83;
    squares of one in the side, 102;
    of six, 103;
    of five, 107, 111

  Right and left, 70

  Robinson, Dr. Louis, 45

  Rods, 76

  Rolled prints, 7, 39, 68

  Roller, 36;
    small, 40

  Royal Institution, 2


  Sand, ridges on, 54

  Scars, 59, 97

  Seal, 22;
    sealing-wax casts, 50

  Seamstresses, 59

  Selection, 20, 209

  Shrimps, 210

  _Signalements_, 156

  Size (glue), 48, 49

  Skin disease on fingers, 122

  Slab, 4, 35, 41

  Slopes, 136;
    on fore-finger, 118

  Smart, Major Charles, 164

  Smoke-prints, 47

  Snow on mountain ranges, 32

  Soda (washing), 36, 41

  Spielman, Isidore, Mr., 192

  Spirals, 74

  Sports, 20, 211

  Squares (interpolations), 10, 101

  Standard patterns, 74, 76;
    the C. set, 177

  Staples, 76, 83

  Stereoscope, 9

  Students, in Art and Science, 197

  Surnames, Hindoo and Chinese, 14, 152

  Swift, Dean, 1

  Symbols for patterns, 144

  Systems of ridges on palm, 54


  Tables, _see_ list of, p. xiii.

  Tabor, Mr., 26

  Tabulations, 179

  Tang dynasty, 25

  Tattoo marks, 97

  Taylor, T. Meadows, Mr., 24

  Teeth, 166

  Tests of calculated Randoms, 173;
    of classification, 179

  Thompson, Gilbert, Mr., 27, 44

  Thrills, their relation to notes, 63

  Thumb, loops on, 200;
    ball of, 96, 98

  _Tipsahi_, 24

  Titchener, E. B., Mr., 62

  Title-page, prints on, 8, 58, 73;
    index-number to them, 135

  Toes, 57

  Tools, callosities caused by, 59

  Transitional patterns, 79, 143, 178

  Triangular plots, 67, 86, 87

  Turpentine, 36

  Twins, 17, 167, 185

  Twist, direction of, 78

  Type, 19, 198


  Ulnar, 70

  United States, system used in, 15, 164


  Variation, 20, 211

  Varnish, prints on when undried, 50

  Velvet, 63


  Wall-paper, 66

  Water colours, 44

  Wax;--sealing, 50;
    dentist's, 50

  Weldon, Prof., 210

  Welsh, the, 17, 192

  Wen-teh, the Empress, 25

  Whitening, 49

  Whorls, 7, 75, 78

  Wundt, Professor, laboratory at Leipzig, 62


THE END


_Printed by_ R. & R. CLARK, _Edinburgh_.




FOOTNOTES:

[1] _Der Tastapparat der Hand der menschlichen Rassen und der Affen._ Dr.
Arthur Kollmann. Leopold Voss, Leipzig, 1883. He has also published a more
recent memoir.

[2] "Morphologie der Tastballen der Saugethiere," _Jahrbuch_, xiv. p. 407.
Leipzig, 1888.

[3] _Ann. Sc. Nat._, 5th series, vol. ix. 1868.

[4] The Latin is obscure. "Mira vallecularum tangentium in interna parte
manus pedisque ... dispositio flexuraque attentionem ... in se trahit."
There are three ways of translating "tangentium," and none of them makes
good sense. In the index of prints he uses the phrase "vallecularum
tactui." It would seem that he looked upon the furrows, and not the
ridges, as the special seat of touch.

[5] The results arrived at by M. Féré in a Memoir (_Comptes Rendus, Soc.
Biologie_, July 2, 1891; Masson, 120 Boulevard St. Germain, Paris) may be
collated with mine. The Memoir is partly a review of my paper in the
_Phil. Trans._, and contains many observations of his own. His data are
derived from epileptics and others mentally affected. He has, by the way,
curiously misinterpreted my views about symmetry.




Transcriber's Notes:

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Subscripted characters are indicated by =subscript=.

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Punctuation has been corrected without note.