THE MAMMALS 



443 



we find cattle, deer, elks, antelopes, goats, sheep, giraffes, camels, and 



llamas. 



Those even-toed ungulates which are not ruminants include the 

 hogs, peccaries, and the hippopotamus. The latter uses four toes on 

 each foot. Even our common pig has four rather well-developed toes, 

 but the second and third are usually the only ones that touch the ground. 



Photo by Winchester 



Fig. 28.19. Mother and baby doing fine. This mother hippopotamus and her week- 

 old baby are representatives of the even-toed ungulates; they use four of their toes, 

 and are thus kin to cattle. These are in the Brookfield Zoo in Chicago. 



Psa/fer/'urr7 



Reticulum 

 tAborr/asum Rumer7 



Animal Biology, Wolcott, McGraw-Hill Book Company, Inc. 



Fig. 28.20. The complex stomach of a ruminant such as a cow. When first eaten 

 the food passes into the rumen ; later balls of this food, called the cud, are passed into 

 the reticulum and up to the esophagus back into the mouth for thorough chewing. On 

 the second swallowing the food passes into the psalterium and on to the abomasum for 



the initiation of digestion. 



Order — Cetacea 



This group includes the whales, porpoises, and dolphins. Whales 

 are sometimes thought of as fish because they live in the water and have 

 a body that is somewhat fish-like in shape. However, they are warm- 



