i6 



ELEMENTS OF PHYSIOLOGY 



other like the blades of scissors ? The incisors are very 

 long in gnawing animals (rats, squirrels, etc.). Next to 

 the two incisors in each quarter of the jaws, comes one 

 canine, so called because the corresponding tooth in the 

 jaws of dogs is well developed ; in cats, tigers, dogs, and 

 other flesh-eating animals, it is suited for tearing. It 

 has only one root, but that is a long one. Could you 

 catch hold with your canine teeth so as to use them for 

 tearing ? Are they sharper than the incisor teeth ? (Use 



FIG. 19. 



a mirror.) The two upper canines are fancifully called the 

 "eye teeth," and the two lower, the " stomach teeth." Next 

 in order behind the canines are the two bicuspids, which 

 are grinding teeth. Their crowns are broad and they 

 have two roots. Last of all come the three large grinders, 

 called molars. Are the grinding surfaces of the molars 

 smooth or rough ? Are they like or unlike the surfaces 

 of the bicuspids ? The last molar in each jaw is called 

 the wisdom tooth, because these teeth do not come until 

 the person is supposed to have reached years of dis- 

 cretion. Activity is the law of life, and the wisdom teeth 



