348 



ELEMENTARY ZOOLOGY. 



ments include, beside the digestive tract itself, the shape 

 and size of jaws, the teeth, the tongue, the lips, the claws, 

 and indeed the very nature and instincts of the animal. 



The teeth are better developed and more differentiated 

 in the mammals than in any other group. The three 

 types are the cutting (incisors) , the tearing (canines) , and 



FIG. 147. Diagram of stomach of a ruminant. After Wiedersheim. 



Questions on the Figure. What is the significance of the term 

 ruminant ? Of what conceivable advantage is this form of stomach ? 

 What animals belong to the class? 



the grinding (molar) teeth. Usually much of the habits 

 and relations of the mammal can be told by a study of the 

 teeth alone. 



Many mammals are gregarious, going in herds or flocks, 

 as is seen in seals, rodents, sheep, deer, wolves, monkeys, 

 and man. This tendency is seen particularly in connec- 

 tion with food getting, polygamous mating, migrations, 

 and defense. 



