NUTRITION PROPER. 



30I 



not necessary, because thorough insalivation is not re- 

 quired for flesh-food (Fig. 184). 



Herbivorous molars are by far the most specialized 

 and complex, because their food requires the most com- 

 plete trituration and insalivation (Fig. 185). 



Fig. 183. — Teeth of the right side of the upper jaw of a hog. 



Undoubtedly the primal mammal was omnivorous 

 and had simple tuberculated molars. From this gener- 



FlG. 184. — Side view of the upper jaw of a dog. 



alized form, as time went on, mammals were specialized 

 in two main directions — the one more and more adapted 



Fig. 185. — Face view of the upper jaw of a sheep. 



to flesh eating, the other to herb eating. The extreme 

 forms are represented now by the cat tribe on the one 

 hand and the ruminants on the other. In the meanwhile 



