36 



A MANUAL OF DENTAL ANATOMY. 



Although it is not strictly true, the masseter and temporal 

 may be said in mammals to be developed in an inverse ratio 

 to one another : when one is large the other is not. 



The masseter is at a maximum in Carnivora, which have 



FIG. 16 



little lateral movement possible to their jaws ; the temporal 

 is also highly developed in many of the class. 



In the great apes, the temporal becomes enormously 

 developed only at the period of second dentition ; this fact, 

 conjoined with its size, which in herbivora seems to have some 

 relation to the presence or absence of canines, would incline 

 one to suppose that it was useful in that rapid closure of the 

 mouth appropriate to biting when animals fight or seize prey. 



The form of the glenoid cavity also bears an intimate 

 relation to the dentition of the animal, and the nature and 

 extent of the movement of its jaws. 



Thus, in a child it is nearly flat, with no well marked 

 surrounding elevations; its axis is transverse, and little 

 rotary motion is made use of. In the adult it is deeply 



(') Condyle of the lower jaw, and glenoid fossa of a tiger. 



