196 AGE OF THE DOMESTIC ANIMALS. 



and the arches of the molars, unevenly ; the inferior tusks are 

 nearer to the incisive arch, while the superior ones are nearer 

 the molars, and when the jaws are closed the tusks cross each 

 other, coming in contact by the postero-external surface of the 

 inferior tusk and the antero-internal face of the superior tusk. 

 The temporary tusks are smaller, longer, more curved, and more 

 ^ pointed than the permanent ones. 



I 



Fig. 176. 

 Permanent dentition of the dog. 



MOLARS. 



There are six molars in each arch of the upper jaw and 

 seven in each arch of the lower. They increase in size from 

 the first premolar to the fourth of the upper jaw, and to the 

 first post-molar (fifth of the lower jaw), and then diminish in 

 size at the next to last and last molar. They have large, 

 bulbous crowns with pointed eminences, which serve for the 

 tearing rather than the grinding of food. In the upper jaw 

 the first three premolars are unilobular, the last is bilobular, 

 and the last two post-molars have flat crowns. In the lower 

 jaw the four premolars are unilobular, the first molar has three 

 eminences, and the last two have two. 



When the teeth of the dog have accomplished their eruption, 

 they cease to grow and their roots remain firmly fixed in the 

 alveolar cavities. In the first dentition only the premolars are 

 found ; the post-molars appear as permanent teeth. 



