Page:Popular Science Monthly Volume 62.djvu/58

52 That the method of employing the prints of the apical patterns in identification, as advocated by Galton is, in the hands of an expert, an exact one, there can be no doubt, and it has been already accepted by the English government and introduced in the province of Bengal and a few other places, proving a dangerous rival to the more obvious but less accurate system of Bertillon, which depends upon various physical measurements; but the disadvantages occurring from the minuteness of the parts upon which the observation depends and the necessity of a lens, obstacles which would demand in all cases the employment of a trained expert, would necessarily limit the application of such a system to a few places where adequate means could be furnished.

As a practical extension of the Galtonian system; one in which the minute details of the apical patterns are replaced by larger and more definite markings, the present author advocates the use of prints, not only of the whole palms, but of the soles as well, a system in which in the vast majority of cases the cursory study of the main lines and areas alone would be sufficient, while only in the almost impossible case of general correspondence in the markings of two individuals in all four members would resort to what Galton terms the 'minutiæ' be necessary. In the collection of one hundred palm prints alluded to above, there are but two or three cases where the general formula is the same in the hands of the same side, and in these the other hands and the two sets of soles are widely different. If this should prove to be about the usual average, then an identity of general plan, that is a similar course in the four primary lines, may be expected to occur once in every 25 left hands. Continuing this line of reasoning, the chance of the coincidence being repeated in the right hand would be but 252, or 625, and if the same figures be true of the soles, then in complete sets the chance of correspondence in the gross details would be 254, or once in 390,625 times. But such 'identity' is by no means a complete one and really means, not an identity at all but a general similarity in the course of the four primary lines and in the areas defined by them. If such very obvious details as the occurrence of patterns, or the condition of the carpal area be also taken into account the chance of coincidence would be many times decreased. Furthermore, as Galton has conclusively proved by careful statistical study of the apical patterns, even in those identical in general plan, the 'minutiae,' that is, the disposition, number and length of the ridges forming the patterns are always very different.

Aside from this, another line of proof of the impossibility of complete duplicates is furnished by an examination of the hands and palms of so-called 'identical' twins, or twins which are of the same sex and otherwise closely resembling one another. In such cases we have a strong biological warrant to expect a closer resemblance in these