530 Hepburn — The Papillary Ridges on the Hands and Feet of Monkejjs and Men. 



certain extent, but in monkeys these muscular groups are comparatively feeble ; 

 and, moreover, muscular growth will not account for the remaining eminences. 

 It may be urged that the terminal phalanges are bulbous in response to the 

 corresponding delicacy of their sense of touch ; but this claim cannot be made on 

 behalf of the other eminences in the hand or foot. 



The three eminences situated in relation to the bases of the digits can scarcely 

 be accounted for by lateral pressure between growing structures, since the digits 

 merely develop as bud-like outgrowths from the free end of a limb, which at first 

 is in reality only a larger bud. 



I am thus led to conclude that all these eminences are sjiecial developments 

 which begin to make their appearance whenever an animal, in the process of its 

 evolution, commences to use its hands and feet for purposes of prehension 

 associated with locomotion, and that the papillary ridges which cover the 

 eminences assist these functions after the manner of the papillary ridges which 

 cover the palm and sole generally. 



Upon the theory so expressed it would naturally follow that the arrangement 

 of the papillary ridges in the palm and sole must be determined by the shajje of 

 the eminences and the nature of the intermediate areas. That this is so, is, I believe, 

 entirely borne out by an examination of the monke}'- impressions. It is certainly 

 a most remarkable fact that the designs or patterns are practically entirely confined 

 to the positions occupied by the various eminences, while in the intermediate areas 

 the papillary ridges are either arranged transversely to the long axis of the digit 

 or member, or with such slight modification of this direction as would place them 

 parallel to the long axis of any cylindrical object which might be grasped by 

 the hand or foot. 



An examination of the hand of Ateles ater — the spider-monkey — in which 

 the pollex is wanting, shows that the papillary ridges deviate, only to a slight 

 extent, from the longitudinal direction even in those areas where we expect to 

 find eminences presenting characteristic designs. I regard this disposition of the 

 papillary ridges as directly associated with the modification in the grasping power 

 of the palm due to the absence of the pollex. Professor Cunningham has kindly 

 supplemented my series of impressions by a few of the hand and foot of the 

 orang-utan. The hand of this important anthropoid, whose habits are largely 

 arboreal, is also noteworthy for its small and rudimentary pollex. In this case 

 the papillary ridges over the greater part of the palm are remarkable for their 

 o-eneral longitudinal direction, and a similar direction prevails over the palmar 

 eminences with the exception of that corresponding to the ball of the rudimentary 

 thumb. • 



Apart from the hook-like manner in which both the orang-utan and the spider 

 monkey use their hands in performing trapeze-like movements, there can be no 



