260 CHARACTERS OF MAMMALIAN TEETH. 



forms for special uses: thus, the front teeth, from being 

 commonly adapted to effect the first coarse division of 

 the food, have been called cutters or incisors ; and the 

 back teeth, which complete its comminution, grinders or 

 molars ; large conical teeth situated behind the incisors, 

 and adapted by being nearer the insertion of the biting 

 muscles to act with greater force, are called holders, 

 tearers, laniaries, or, more commonly, canine teeth, from 

 being well developed in the dog and other carnivora. 



Molar teeth, which are adapted for mastication, have 

 either tuberculate, or transversely ridged, or flat summits, 

 and usually are either surrounded by a ridge of enamel, 

 or are traversed by similar ridges arranged in various 

 patterns. 



The large molars of the capybara and elephant have 

 the crown cleft into a numerous series of compressed 

 transverse plates, cemented together side by side. 



The teeth of the mammalia have usually so much more 

 definite and complex a form than those of fishes and rep- 

 tiles, that three parts are recognized in them, viz: the 

 "fang," the "neck," and the "crown." The fang or root 

 {radix) is the inserted part ; the crown {corona) the ex- 

 posed part ; and the constriction which divides these is 

 is called the neck {cervix). 



Fixation". — It is peculiar to the class mammalia to 

 have teeth implanted in sockets by two or more fangs; 

 but this can only happen to teeth of limited growth, and 

 generally characterizes the molars and premolars; perpe- 

 tually growing teeth require the base to be kept simple 

 and widely excavated for the persistent pulp. In no 

 mammiferous animal does anchylosis of the tooth with the 

 jaw constitute a normal mode of attachment. Each tooth 

 has its particular socket, to which it firmly adheres by 



