MOVEMENTS OF TrlK JAWS. 145 



is likewise varied according to the particular 

 movements required to act upon the food in the 

 different tribes. The articulation of the lower 

 jaw with the temporal bone of the skull ap- 

 proaches to a hinge joint ; but considerable lati- 

 tude is allowed to its motions by thfe interposi- 

 tion of a moveable cartilage between the two 

 surfaces of articulation, a contrivance admirably 

 answering the intended purpose. Hence, in ad- 

 dition to the principal movements of opening 

 and shutting, which are made in a vertical 

 direction, the lower jaw has also some degree of 

 mobility in a horizontal or lateral direction, and 

 is likewise capable of being moved backwards 

 or forwards to a certain extent. The muscles 

 which effect the closing of the jaw are princi- 

 pally the temporal and the masseter muscles ; 

 the former occupying the hollow of the temples, 

 the latter connecting the lower angle of the jaw 

 with the zygomatic arch. The lateral motions 

 of the jaw are effected by muscles placed inter- 

 nally between the sides of the jaw and the basis 

 of the skull. 



In the conformation of the teeth and jaws, a 

 remarkable contrast is presented between car- 

 nivorous and herbivorous animals. In the for- 

 mer, of which the Tiger, Fig. -274, may be taken 

 as an example, the whole apparatus for masti- 

 cation is calculated for the destruction of life, 

 and for tearing and dividing the fleshy fibres. 



VOL. II. L 



