“It is now a well ascertained fact that every person bears on his fingers as certain proof of his identity as he does on his face. The latter is, however, that part of his anatomy by which he is most readily identified by the world at large, though to his intimate friends other particulars about him may characterise him equally strongly. By means of the eye, the tout ensemble of the countenance is registered upon the mind, generally regardless of details respecting the actual form of each particular feature—in short, a person is recognized and identified by exactly the same psychological process as a printed or written word is read without first spelling it.”
It must be clear to any student of the subject that persistence of patterns must become the basis of identification in this way, and that persistence is now as firmly established as anything can be as to living creatures.
Sir Edward Henry, in his Finger-Prints, says (p. 17, 3rd edition): “Impressions being required for permanent record, their utility must, in great measure, be contingent upon the persistence through long periods of time, of the general form of the pattern and of the details of the ridges constituting it.” No such stability has yet been shown to exist in regard to any other part of the body. The bones change very greatly, not only in size, but in shape, texture, and mechanical conditions through life. Even the ordinary features and expression of a human being by no means can be said to remain uniform. One sees a friend during many short intervals, and is not finely observant of minute changes that in a decade or two amount collectively to an almost complete transformation of the man’s whole face and figure. The photographic system of identification, although serving a purpose now and then, was found, therefore, to be untrustworthy.
My revered teacher, Lord Lister, noted the slow migrations of the pigmentary particles that make the web-like patterns on a frog’s foot. I have observed similar but still slower changes in ordinary freckles on a human hand. The white spots of leucoderma—a skin-disease that used to be confused with leprosy, from which it entirely differs—are often bounded with dark borders, into which the pigment particles have migrated from the white spots. A negro’s skin sometimes becomes white where a fly-blister has been applied, as a fair-skinned person is often marked with a dark patch after a similar application. The pigment particles move to and fro like living things, though very slowly, and the marks they collectively make on a living body are not fixed and stable. Again, we have seen that the police used to record the position of wens, tumours, tattoo marks and the like. But tumours are now often removed through the line of natural creases, or wrinkles, leaving very faint traces, if any, behind.
An official in Japan had a large wen on his forehead, which disfigured him greatly. He was getting elderly, and told me, when friends brought him, that he would as soon have the wen as a scar. I got him to consent to have it removed through the natural wrinkle in the forehead, after which it left no visible trace at all.
A curious case was that of a man whose back and shoulders were adorned by a large collection of a certain kind of tumour varying from the size of a chestnut to that of a hen’s egg. They all disappeared, without the use of the knife, leaving no scar behind, and only a slight lowering and thinning of the skin.
Even scars, themselves, sometimes very unsightly ones, tone away to a large extent, till they cease to be at all conspicuous. The colour of the hair changes greatly in some people at the various stages of life. Certain diseases, too, such as malarious affections, the action of the sun, and certain employments, change the complexion in a very remarkable way.
What the pole-star used to be in navigation, fingerprint patterns are now become for all serious purposes of practical identification.