SCIENTIFIC DETECTION OF CRIME — SANNIE 347 



50 years past, no two identical prints have ever been discovered. Ex- 

 perience, in this case, has confirmed theoretical calculation. 



When a fingerprint is examined in detail, it will be seen that it is 

 made up of a series of ridges and depressions, running parallel to one 

 another and arranged more or less regularly around a central point 

 roughly in the center of the fleshy pad. These ridges form either 

 more or less flattened arches, or loops, opening to the right or left, 

 or, again, more or less complicated whorls. At the base of the finger, 

 there is a system of ridges roughly parallel to the line at the joint. 

 The meeting place of this system and the other is formed by triangular 

 points in the shape of a Greek "delta," by which name they are, in- 

 cidentally, known. 



These papillary ridges are not absolutely regular, however; in some 

 cases, they are broken and end abruptly ; in others, they split in two ; 

 in yet others, they form islands between two longer ridges. Each of 

 these irregularities is useful for identification purposes. Taking their 

 presence and position in the print as a basis, Balthazard, by a simple 

 calculation of probabilities, has shown that approximately 1,074 mil- 

 lion prints would have to be examined to find two prints showing 15 

 points of coincidence in the ending of their lines or their bifurcations. 



The first joint of one finger alone contains more than 100 of these 

 identification points. One finger can therefore definitely reveal the 

 identity of an individual, and indeed a portion of a print may be 

 enough. The whole system of fingerprints is based on this principle. 



Lastly, a fingerprint is extremely easy to take. All that is needed is 

 a plate covered with ink on which the finger can be rolled. Finger- 

 prints are thus the ideal morphological characteristic for identifying 

 individuals; throughout the world, they have taken the place of Ber- 

 tillon's bone measurements, which are now of no more than historical 

 interest. 



It is not enough, however, to have found the ideal morphological 

 characteristic ; it must also be suitable for use in a card index system 

 and for the tracing of cards. Several methods are used ; in the English- 

 speaking countries, they are derived from the Galton-Henry system 

 and in the Latin countries from the Vucetich system. All these sys- 

 tems use the basic ridge patterns of the fingertips and differ in their 

 methods of secondary classifications. Prints are traced by going 

 through the files themselves. 



It might be thought that no further progress could be made in such 

 a field ; and indeed the largest filing systems, sometimes including sev- 

 eral tens of millions of cards, are entirely satisfactory. Nonetheless, 

 a mathematical study of the problem of tracing an object with rather 

 indeterminate characteristics among a group of similar objects has re- 

 cently made possible a considerable improvement in the tracing tech- 

 nique, thanks to the use of a supplementary card index made up of 



