146 THE VltAL FUNCTIONS. 



The molar teeth are armed with pointed emi- 

 nences, which correspond in the opposite jaws, 



so as exactly to lock into one another, like 

 wheelwork, when the mouth is closed. All the 

 muscles which close the jaw are of enormous 

 size and strength ; and they imprint the bones 

 of the skull with deep hollows, in which we 

 trace marks of the most powerful action. The 

 temporal muscles occupy the whole of the sides 

 of the skull (t, t) ; and by the continuance of 

 their vigorous exertions, during the growth of 

 the animal, alter so considerably the form of the 

 bones, that the skulls of the young and the old 

 animals are often with difficulty recognised as 

 belonging to the same species.* The process of 

 the lower jaw (seen between t and t), to which 

 this temporal muscle is attached, is large and 

 prominent ; and the arch of bone (z), from which 



* This is remarkably the case with the Bear, the skull of 

 which exhibits in old animals a large vertical crest, not met with 

 at an early period of life. 



