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ANIMAL BIOLOGY 



example, have sharp cutting teeth (incisors) and grinding teeth 

 (molars). Others, e.g. dogs, cats, lions, and tigers, have sharp pointed 

 incisors and molars and in addition long canine teeth for tearing 

 their food. In horses, cows, and other herbivorous animals the 

 grinding teeth are especially developed, while canine teeth are either 

 wanting or are relatively small. 



All these animals have four legs, but the relative size of the front 

 and hind legs may differ greatly. In a kangaroo, for instance, the 



JUetouArpal Bones "' 



FIG. 137. Skeleton of the horse. 



hind legs are very large, while the front pair are so small as to be 

 practically useless. Then, too, the nails on the toes vary con- 

 siderably. The fingers and toes of man are protected on a surface 

 by nails. A horse has only one toe on each foot, and the nail for 

 that toe is developed into a hoof. Cows and sheep have two toes 

 on each foot similarly protected. On this account these mammals 

 and others like them are called the hoofed mammals. 



