112 MAN AND THE LOWER ANIMALS n 



prise four incisors, two canines, four small grinders, 

 called premolars or false molars, and six large 

 grinders, or true molars in each jaw making thirty- 

 two in all. The internal incisors are larger than 

 the external pair, in the upper jaw, smaller than 

 the external pair, in the lower jaw. The crowns of 

 the upper molars exhibit four cusps, or blunt- 

 pointed elevations, and a ridge crosses the crown 

 obliquely, from the inner, anterior cusp to the 

 outer, posterior cusp (Fig. 18 m 2 ). The anterior 

 lower molars have five cusps, three external and 

 two internal. The premolars have two cusps, one 

 internal and one external, of which the outer is the 

 higher. 



In all these respects the dentition of the Gorilla 

 may be described in the same terms as that of Man ; 

 but in other matters it exhibits many and import- 

 ant differences (Fig. 18). 



Thus the teeth of man constitute a regular and 

 even series without any break and without any 

 marked projection of one tooth above the level of 

 the rest ; a peculiarity which, as Cuvier long ago 

 showed, is shared by no other mammal save one 

 as different a creature from man as can well be 

 imagined namely, the long extinct Anoplotherium, 

 The teeth of the Gorilla, on the contrary, exhibit 

 a break, or interval, termed the diastema, in both 

 jaws : in front of the eye-tooth, or between it and 

 the outer incisor, in the upper jaw ; behind the eye- 

 tooth, or between it arid the front false molar, in the 



