Mammalia: Classification 



759 



Fig. 573 {Left). Okapi group, Africa. (Courtesy, American Museum of Natural 

 History, New York.) 



Fig. 574 (Right). Head of antelope, Gazella grant i. showing horns. (Courtesy, 

 Flower and Lydekker: "Introduction to the Study of Mammals," London, A. & C. 

 Black, Ltd.) 



into one or two strong digits, the elephant retains all five on each foot 

 and all are functional. The five, however, are not externally free. 

 Spread far apart, they are enclosed in a common covering of skin, and 

 the wide interstices between them are filled with dense connective 

 tissue which continues into a thick pad of similar tissue built out behind 

 the row of digits. Each digit of the manus bears a large broad hoof; in 

 the pes at least three or four digits have hoofs. By this highly special- 

 ized structure of the foot, the tremendous weight which it must sustain 

 is distributed over a maximum area of ground. The horse walks on the 

 tips of four toes, one on each foot. The elephant walks on 20 toes, but 

 each set of five is so constructed that it is functionally a single enormous 

 hoof-like member. Each leg is a massive straight column. The back- 

 ward bend at the elbow and the forward bend at the knee, character- 

 istic of other mammals, are necessarily eliminated, being incompatible 

 with efficient support of the animal's weight. 



