Cat, etc., are Carnivores. Bats, Skunks, Shrews and 

 Moles, are Insectivores, while Wood-chucks, Squirrels, 

 Wood rats. Deer, and many Mice are Herbivores. The 

 beasts of prey have teeth adapted to tearing flesh and 

 crushing bones; plant-eaters have teeth fitted for crop- 

 ping plants and triturating vegetable tissues; insect- 

 eaters have teeth with numerous sharp-pointed cusps, 

 and some of these animals, like the ant-eaters, have no 

 teeth at all. Usually, in the different groups of mam- 

 mals, the number of teeth is fixed and more or less 

 constant. There are four distinct types of teeth in mam- 

 mals: (1) Incisors, or front teeth, which are sharp, 

 and more or less elongated, according to the group. 

 They are used chiefly for biting and gnawing: (2) 

 Canines, or eye teeth, of which there is only one on 

 each side next to the incisors; (3) the PREMOLARS, 

 called the bicuspids in man, which are the anterior 

 grinding teeth. These are located just back of the 

 canines, and (4) the MOLARS, or posterior grinding 

 teeth. These are the hindermost teeth and have more 

 nearly flattened surfaces. As a rule, mammals have two 

 sets of teeth during a lifetime. The first series is tem- 

 porary and is called the "milk teeth." This series usu- 

 ally differs considerably from the adult dentition. For 

 instance, in humans the posterior molars are not present 

 in the milk or baby teeth. While in man there are the 

 same number of each kind of teeth in both jaws, upper 

 and lower, this is not always the case in all animals. 

 For example, the sheep, which is an herbivorous ani- 

 mal, has no incisors or canines in the upper jaw, but it 

 has three incisors and one canine on each side of the 

 lower jaw. 



The structure of mammalian teeth varies so great- 

 ly that it would be necessary to indulge in a detailed 



-^ 42 >«.- 



