102 OUR BODIES AND HOW WE LIVE 



crushed and ground into small pieces by the teeth. 

 This process is called chewing or mastication. 



147. The Teeth. The teeth serve to cut and grind the 

 food. They are fastened into the jaws by roots, which 

 sink into the bony sockets somewhat in the same way as 

 a nail is held in a piece of wood. 



A child at birth has no teeth ; afterwards, however, two 

 sets are developed, one after the other. The first set, or 



FIG. 64. The Temporary and Permanent Teeth. 



Temporary Teeth: A, central incisors; B, lateral incisors; C, canines; D, anterior 

 molars ; E, posterior molars. Permanent Teeth : F, central incisors ; H, lateral 

 incisors; K, canines; Z,, first bicuspids ; M, second bicuspids ; N, first molars. 



temporary, often called the milk teeth, twenty in number, 

 are shed in childhood. The second set, or permanent teeth, 

 thirty-two in number, gradually take their place. 



The teeth are arranged in the same way, and number 

 the same in each jaw and in each half of each jaw. 



