112 MAN AND THE LOWER ANIMALS. n 



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 an- 

 terior 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 Go- 

 rilla may be described in the same terms as that of 

 Man; but in other matters it exhibit's many and 

 important 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 Anoplotherl- 

 um. 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 and the front false 

 molar, in the lower jaw. Into this break in the 

 series, in each jaw, fits the canine of the opposite 

 jaw; the size of the eye-tooth in the Gorilla being 

 so great that it projects, like a tusk, far beyond 

 the general level of the other teeth. The roots of 

 the false molar teeth of the Gorilla, again, are 



