FINGER-PRINT PATTERNS
Before reading this chapter, let the reader carefully examine the clear
lineations shown so well in the photographic picture of the Zebra’s
stripes, opposite. They will be found to resemble very closely the
lineations on the skin of human fingers, as printed when enlarged by
photography, forming very similar patterns. Similar linings occur in
the hide of the tiger.
[Illustration: GREVY’S ZEBRA.--Showing Lineations like Finger-Print
Patterns.]
[Photo. Pictorial Agency]
Where two lines, beginning as parallels, curve to divide, a fresh line
begins to appear between. Sometimes a single line forks into two or
three. Again, triangular arrangements of lineations are seen on the
zebra, and one can trace some of these back into lines running as a
parallel series. Surely the causes which produce the ridges on a human
or anthropoid finger cannot be quite the same biologically as lead
to the formation of similar patterns in the skin of the zebra. There
are mechanical or physical conditions, however, which condition the
formation of ridges in a sandy shore, of powdery snow blown by the
wind and tossed on a smooth frozen lake, as has already been noticed,
and these conditions are being carefully elucidated by scientific
observers. But why living tissues should produce patterns like those,
just in those positions, and then reproduce them in living descendants
with slight but important variations, is a totally different question,
the answer to which must be reached in a different way.
While the ridges and furrows lie in parallels or curve in the same
direction over some considerable surface of the sole and palm, they
also gather up into more or less intricate, scroll-like patterns
at various points besides those of the last joints of the fingers,
which have chiefly engrossed popular attention hitherto. In man, the
lemurs, lemuroids, and apes, these pattern points are numerous. In my
own hands, there are on the left hand, besides the five finger-tip
patterns, other five like them, and the right hand contains six.
There are thus twenty-one _complex_ patterns which might be used for
identification.
On the other hand, when one reads of a mathematical attempt to compute
the probabilities of two finger-prints being alike, it is not a
question simply of comparing an unknown finger smudge with collections
containing ten finger-prints each, for the unknown smudge may have
been made, not from one of a possible set of ten finger-tip prints,
but from one of those other local patterns not on the finger-tips at
all. There is a saying often attributed to Huxley, who certainly used
it wisely, that the value of grist from the mathematical mill depends
on the quality of the corn put into the hopper. But official amateur
mathematicians have made many much worse mistakes than the above in
regard to probabilities in the realm of finger-print evidence.
In a few cases, especially in the feet patterns, often a very plain
character, parallel or slightly wavy lines of no precise design, so to
speak, may be found. A short time ago, when applying mustard to the
feet of a lady in some kind of fit, I observed this almost featureless
pattern in her toes. If such cases were as common in the hands as
they are rare, the finger-print method would hardly be of any avail
for identification. A teleologist of the old school of Paley might
argue with some plausibility that the possible usefulness of those
intricate patterns was the true meaning of their existence, otherwise
not yet explainable. That the old Paleyan conception of nature having
an end or purpose in view, the teleological explanation of things as
useful to the being possessing them, had its own usefulness in giving
a broader view of natural history facts in their interrelations, is
borne out even by so great an authority as Charles Darwin himself.
Are the markings in a bird’s eggs recognized by the sitting bird in
those cases where the markings are peculiar--and some are like written
characters--or are they purely accidental and useless? A correspondent
in _The Country-Side_ wrote a short time ago, describing a test case he
observed of a thrush in his possession. This bird built a nest and laid
therein five eggs, “varying in size from a good-sized pea to the normal
size. The smaller ones I took away and substituted one from a wild
bird’s nest; this the following day I found laid at the bottom of the
aviary smashed. I again repeated the addition with the same result. I
had carefully marked the eggs, so that there could be no mistake.” The
writer signed himself “W. A., Wimbledon.”
Dr. Wallace’s view, as I understand it, is that variations in wild
animals were due chiefly to immunity from enemies, allowing free
play to the natural tendency to variation, kept only in check by its
dangers, such as leading to betrayal by conspicuous colouring, and so
on. Professor Poulton in _The Colours of Animals_, 2nd ed. p. 212,
says:--
“It is very probable that the great variation in the colours and
markings of birds’ eggs, which are laid close together in immense
numbers, may possess this significance, enabling each bird to know
its own eggs. I owe this suggestive interpretation to my friend,
Mr. Francis Gotch: it is greatly to be hoped that experimental
confirmation may be forthcoming. The suggestion could be easily
tested by altering the position of the eggs and modifying their
appearance by painting. Mr. Gotch’s hypothesis was formed after
seeing a large number of eggs of the guillemot in their natural
surroundings.”
Australian ewes know the bleat of their own lambs, however immense the
flock, and all through nature we find this useful note of recognition.
One of the most philosophic interpreters of living phenomena, viewing
things from a very recent standpoint--Professor J. Arthur Thomson,
in his fascinating _Biology of the Seasons_ (p. 174), writing of the
colour and texture of birds’ eggs, says:--
“In some cases, it is said, the shell registers hybridism--a very
remarkable fact. It is another illustration of the great, though
still vague, truth that the living creature is a unity through and
through, specific even in the structure of the egg-shell within
which it is developed. For although the shell is secreted by the
walls of the oviduct, it seems to be in some measure controlled by
the life of the giant-cell--the ovum--within.”
Such pattern-forming qualities are found in many fields of nature, very
beautifully, for example, as we have seen, in the skin of the zebra;
on the back of a mackerel; in the grain of various kinds of wood; in
the veining of leaves and petals; and in the covering or substance of
seeds such as the nutmeg and scarlet runner bean. Sir Charles Lyell, in
his _Elements of Geology_, figures the ribbing of sand on the sea-shore
in a wood-cut which might be an enlarged diagram of human skin. (See
fig. on page 32). In his _Principles of Geology_ (5th ed., vol. i.,
p. 323) there is, again, a figure described as a section of “spheroidal
concretionary Travertine,” which contains many linings strikingly like
those with which we have to deal in this little work.
[Illustration: _a_. section of pine-wood stem.
_b_. a human thumb-print.]
It follows from these analogies that a method of analysing and
classifying such patterns might have very wide utilities beyond its
relation to finger-prints. It is easy, for example, to recognize the
same zebra in quite different pictures. Another point of practical
importance is this, that a smudgy or blotchy impression, supposed to
be that of a criminal present at some seat of crime, might be the
impressed copy merely of some object or texture other than human
skin, but containing lineations of similar arrangement. An outworn
transversely cut branch of a tree might readily produce a print like
that of a human finger. An expert would probably notice that in the
lineations there were no real junctions, each woody ring remaining
apart from the others; but, again, there are some human fingers of such
patterns. I think the bloody smear officially reproduced as impressed
on a post-card in facsimile, and purporting to have come from “Jack
the Ripper,” at the time of the Whitechapel horrors in the eighties,
may have been produced by the sleeve of a twilled coat smeared with
blood. It contained no characters specially characteristic of skin
lineations, which it was presumed to be an example of, as impressed.
Apart from all that, lemurs, lemuroids, apes, anthropoids, and
monkeys, all show on hands and feet, skin lineations in patterns
similar to those of man. In the anthropoid apes it would not be easy
to discriminate them from those of human beings. Some of these were
figured in my _Guide_, and Dr. Otto Schlaginhaufen has supplied
numerous good prints.
If Edgar A. Poe, in his famous mystery of evil deeds done by a
gigantic ape, had been acquainted with finger-print methods, he might
have pictured the police as still more mystified by the imprints of
seemingly human hands.
There are two methods of observing systematically the lineation
patterns.
1.--_The Direct Mode._--This might be done simply by many people by
looking at the lineations with the unaided vision. Till quite recently
the author found no difficulty in doing this, with myopic eyes that
could see something of the texture of a house-fly’s eyes in a good
light. My earliest observations of the finger-patterns were made in
this way, while the patterns were reproduced in pencilled outlines. The
condition of the actual ridges and furrows themselves, with their open
and acting or closed and dormant sweat-pores, ought to be familiar to
the student of dactylography, who is apt to narrow his vision by the
contemplation only of dead impressions made in ink or otherwise. A
lens such as botanists use for field work is very useful, and a high
power is neither necessary nor very helpful. Drawings of the patterns
ought to be made from time to time with coloured or “lead” pencils, and
those drawings should be accurately adjusted by the use of rubber and
compasses.
2.--_The Indirect Method._--This is done by the medium of casts and
printed impressions. Casts may be made of clay, putty, sealing-wax,
beeswax, gutta-percha, hard paraffin, varnish, half-dry paint, and the
like. Printed impressions or dactylographs may be obtained from greasy
or sweaty fingers, blood, printer’s ink, or various substitutes for it.
Within this method, again, two very distinct and complementary kinds of
results may be obtained, which I have elsewhere described as Positive
and Negative. The first or Positive is that, for example, which is
used officially for the record of convicted prisoners by printing with
ordinary printer’s ink, just as a veined leaf or fern, or a box-wood
engraving is printed from. Here the ridges or raised lines appear
black on a white ground, while the intervening furrows appear white,
as do also the minute pores dotted along the crest of each ridge. (See
frontispiece.)
In the other method, as when the fingers are impressed on a carefully
smoked surface of glass, the projecting ridges lift up the carbon
of the soot, leaving a white pattern behind, with the sweat-pores
forming black punctuations, while the receding furrows leave the black
surface untouched. When such impressions have to be used again, as for
evidence, they should be carefully varnished, as they are exceedingly
liable to be destroyed by the slightest contact.
In a case under judicial investigation where an official imprint had
to be compared with one done by accident negatively on smoked glass or
the like, the black lineations would not closely correspond--would, in
fact, considerably diverge in pattern. This might tend to confuse judge
and jury if the distinction of negative and positive dactylograph were
not made clear by the expert witness. Then the apparent divergences
could easily be demonstrated to be very significant coincidences.
Five years of my early life were spent in learning a trade in
Glasgow--that of the soon-to-be-obsolete Paisley shawl manufacture. It
seemed to me to have been an utter waste of time, but part of my duty
was to deal with the arrangement, classifying, and numbering immense
varieties of patterns, printed with every conceivable variation of
combined colours. It was impossible to carry these on memory, and one
had to resort to mnemonic means of classification.
Now, the immense significance of the variety in human finger-patterns
dawned upon me very early, when I had once begun to interest myself in
them.
[Illustration: DESIGN-LIKE PATTERNS IN FINGER-PRINTS NO. 1.
(Diagrammatic)]
[Illustration: DESIGN-LIKE PATTERNS NO. 2.]
There are many patterns, which, when analysed into their composing
elements, present analogies to artistic designs, a view which is no
mere personal fad, but has been affirmed with enthusiasm by many
artists in designs to whom I have pointed out those figures. Here
are a few, by way of illustrating this point (space will not permit
of more). Those figures are from real human finger-prints rendered
diagrammatically. This is the first step, then, to catch with the eye
the pattern or design; give it a class name, and you have at once
established some practical basis of classification in finger-prints.
Then it is possible to frame some kind of catalogue for reference
arranged like a dictionary with its sub-alphabetic order, in an almost
infinite series. The initial difficulty is generally that which
arises from want of skill in printing, which technical points will be
considered subsequently. A soft and flexible substance like the ridges
in human fingers does not always yield an exactly similar impression
in two successive moments, under varying conditions of temperature,
fatigue, and the like. Nor does the analogy of mathematical diagrams
always fitly apply in such a case. Even in steel engravings and fine
etchings, as the connoisseur well knows, the degree of intensity of
the pressure and other conditions will modify to some slight extent
the resulting imprint, but what I wish to emphasize is, that if the
original pattern had any value at all resulting from its complexity
as a pattern, the variation in printing as now done officially by
experienced police officials will not impair much its value as evidence
of personal identity in a court of law. Even the amateur will soon,
after a little practice with good materials, attain a very fair amount
of clearness and uniformity in his imprints.