262 



SKELETONS OP THE LOWER ANIMALS 



bones are modified to serve different uses. Nature's 

 economy in this respect is remarkable. For example, in 

 Figure 111 note the arrangement of the hands in the mole 

 and their adaptations for digging. Note, also, in the cat 

 the development of the finger and toe nails into claws for 

 tearing. The flipper of the whale shows a structure very 

 similar to that of the fins of the fish; in the horse and 

 the cow, the development of the nail into hoofs and the 

 reduction of the metacarpals into a single bone support, 



Fig. 112— Typical skulls ; A, of man ; B, of cow ; 0, of bat ; D, of mole ; E, of 

 cat ; E, of horse : Q, of whale. 



is interesting. In the bat, the enormously elongated 

 phalanges serve as a framework for the membranous wings. 

 Note, also, the differences in the legs of these animals 

 from that of man. In man, the whole foot rests on the 

 ground; while in the cat, the horse, and the cow the toes 

 alone support the body, thus permitting the development of 

 powerful thigh and calf muscles at points where they will 



