THE PHYSIOLOGY OF THE SENSE OF TOUCH 149 



ness of touch and cannot be explained at all on the prehension 

 or friction theory. Dr. Hepburn's view of the various patterns 

 is, that they are secondary to, or dependent on, the shape of the 

 eminences on which they are situated, indeed, that in this respect, 

 they are by-products. It is not intended here to attempt any 

 proof that the individual patterns are physiological arrangements 

 adapted to improving the sense of touch, though this view of 

 them has been well shown by Ch. Fere,* but to prove that touch- 

 sensation rather than prehension determines the changes of 

 pattern exhibited by the Primates in the long course of their 

 evolution. It is worthy of special note here, that the papillary 

 ridges on the hand and foot of man display remarkable changes 

 from their congeners, which agree with the growing complexity 

 of the actions both of palm and digits of the hand and digits of 

 the foot. Man no longer employs his hands only in the two 

 simple modes of prehension, which are general in monkeys and 

 apes, but in very varied ways he combines the functions of 

 his opposable thumb and digits in handhng objects of all sizes 

 and shapes, and minutely apphes his sensitive pulps to divers 

 objects for the purpose of discrimination. 



When the foot of man is compared with those of the Anthro- 

 poid Apes, the most striking point is the extremely simple trans- 

 verse arrangement of the ridges, except on the ball of the hallux 

 and the pulps of the digits and occasional patterns on the inter- 

 digital pads. This is significant of a great change of function 

 and, from one point of view, in the direction of degradation of 

 function. In the Monkeys we find the foot exercising support, 

 progression, and simple prehension ; in the Anthropoid Apes, 

 support, progression, and more complicated prehension, in Man, 

 support and progression alone. These facts as to the functions 

 of Man's foot and the change of pattern of the ridges, prove that 

 other functions than the simple one of prehension determine 

 not only the degree of development of the individual ridges, but 

 also their mode of arrangement. When it is taken into account 

 that Man has not for many thousands of years employed his foot 

 in prehension, and that when he did so employ it he must have 

 * See pp. 172 and 173 (Literature). 



