HISTORY OF THE HUMAN BODY 



most typical, and are in the form of concentric circles, the 

 center coincident with the summit of the pad. The spiral form 



II 



IV 



FIG. 24. Ventral surface of anterior chiridium of an insectivore and of 

 a primate showing correspondence between relief and arrangement of 

 friction ridges. [After Miss WHIPPLE.] 



(a) Croddnra caerulea (shrew-mouse). Fore paw showing walking-pads enclosed 

 by triangular folds of skin, (b) Macacus sp? (Old World monkey). Hand, covered 

 by friction ridges, the arrangement of which corresponds to the relief of (a). 

 The pads are represented by concentric circles, and the triangular folds by triradii. 

 These latter features are here designated by heavy lines, although in the real object 

 they are not more conspicuous than the others. 



of the hypothenar is a degeneration from the primitive type, 

 to which it is connected by the existence of transitional forms, 

 either in other individuals of the same species or in different 



