206 



AGE OF THE DOMESTIC ANIMALS. 



longer, in proportion to the size of the crowns, than those of 

 the adult set. There are only twenty teeth in the deciduous 

 set, — four incisors, two cuspids, and four molars in each jaw. 

 Figs. 190 and 191 represent the temporary teeth, — superior 

 and inferior. There are no bicuspids and no third molars or 

 wisdom-teeth in the temporary set. Four bicuspids and two 

 wisdom-teeth in each jaw, — twelve in all, — which are not in 

 the deciduous or temporary set, make the permanent set to con- 

 sist of thirty-two teeth. 



The surfaces of the teeth which are toward the lips are 

 called " labial ; " toward the cheeks, " buccal ; " toward the 

 tongue, on the lower jaw, " lingual ; " and toward the roof of 

 the mouth, on the upper jaw, " palatal." The surfaces next to 

 each other are called " approximal ; " those looking toward the 



Fig. 187. 



¥ui. 188. 



Fig. 18i». 



centre, " mesial ; " and those looking from the centre, ''distal."" 

 The parts of the six front teetli of both jaws which come in 

 contact with each other are called the " cutting edges," and the 

 broad surfaces of the bicuspids and molars which are brought 

 in contact in the act of masticating are called the " grinding or 

 articulating surfaces." 



The structure of the teeth is approximately that of the 

 tush-tooth of the horse or of the molars of the dog, consisting' 

 of a central pulp covered with dentine, which makes up the 

 bulk of the tooth, and which is again covered with enamel. 

 The cement in man covers the root onl//, or at most only slightly 

 overlaps the enamel. 



Figs. 187 and 188 represent a central incisor and a molar, 

 split vertically so as to show their various parts. A is the 



