TEETH AND JAWS OF MAMMALIA. 129 



these are called the false molar teeth, and also, 

 from their having generally two points, or cusps, 

 the hicKspidate teeth. Tlie posterior molar teeth 

 are differently shaped in carnivorous animals ; for 

 they are raised into sharp and often serrated ridges, 

 having many of the properties of cutting teeth. 

 In insectivorous and frugivorous animals, their sur- 

 face presents prominent tubercles, either pointed or 

 rounded, for pounding the food ; while in quadru- 

 peds that feed on grass or grain, they are flat and 

 rough, for the purpose simply of grinding. 



The apparatus for giving motion to the jaws is 

 likewise varied according to the particular move- 

 ments required to act upon the food in the diflterent 

 tribes. The articulation of the lower jaw with the 

 temporal bone of the skull approaches to a hinge 

 joint; but considerable latitude is allowed to its 

 motions by the interposition of a moveable carti- 

 lage between the two surfaces of articulation, a 

 contrivance admirably answering the intended 

 purpose. Hence, in addition to the principal move- 

 ments 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 and forwards to a certain extent. The 

 muscles which effect the closing of the jaw are 

 principally 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 internally, 

 between the sides of the jaw and the basis of the 

 skull. 



VOL. II. K 



