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 _minutiae_ (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 minutiae, 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 aet. 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 x 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 deg., and complete identity as

100 deg. 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 deg. 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 striae 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 striae.

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 x 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 x 2-1/2 x 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 x 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 _Minutiae_ 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 papillae 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 papillae 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 x 6 x 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 _minutiae_ 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 Minutiae.]

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 x 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.