170 CHARLES MIDLO AND HAROLD CUMMINS 



Pongidae and Homo are generally characterized by lowered 

 pads, far less marked than in monkeys though not so reduced 

 as in Hylobatidae. Such variations, together with the local 

 peculiarities involving single pads, are doubtless associated 

 with functional specializations. The influences which modify 

 pads are regarded as the primary evolutionary agency, while 

 the secondary responses of dermatoglyphics to the modifi- 

 cations of pads are thought to be of negligible moment in the 

 evolutionary process. It is apparent that the elaboration of 

 epidermal ridges and the progressive spreading of areas bear- 

 ing ridged skin may have real significance in the phylogenetic 

 scale, but specific arrangements of these ridges are question- 

 ably adequate as primary foci of evolution. 



In analyzing the functional significance of volar pads it 

 seems safe to take the position, with Whipple and others, 

 that their primitive functional service is concerned with 

 walking. Volar pads are distributed widely among the orders 

 of mammals, both marsupial and placental. The carnivores 

 may be selected as typical of the walking mammals having 

 pads, and it is this group which is referred to as a standard 

 of pads which are not ordinarily used in prehension; the 

 pads of these strictly walking mammals are lacking in dermato- 

 glyphics. The consistency of the pads in carnivores generally 

 is much firmer than in animals in which prehension assumes 

 an appreciable role, and the pads are much more prominent 

 and discrete. Modifications of the morphologic plan occurring 

 in carnivores take the form of fusions of adjoining pads or 

 the loss of components of the plan in company with deviations 

 from pentadactyl construction of the member. Emphasis 

 should be given the fact that different representatives within 

 the same order of mammals may be unlike with regard to 

 the use of the members and the character of the pads. In the 

 carnivores, for example, there are some forms, such as 

 Procyon, which use the anterior members to a large extent 

 in prehension as well as walking. Here the pads present a 

 modification of a different kind. They are lower than the 

 pads of carnivores generally, less discretely outlined at their 



