98 ' THE RELATIONS OF MAN 



Man is provided with two sets of teeth — milk teeth 

 and permanent teeth. The former consist of four incisors, 

 or cutting-teeth ; two canines, or eye-teeth ; and four mo- 

 lars, or grinders, in each jaw, making twenty in all. The 

 latter (Fig. 18) comprise 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 ex- 

 ternal 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^). The anterior 

 lower molars have five cusps, three external and two in- 

 ternal. 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 important differences 

 (Fig. 18). 



Thus the teeth of man constitute a regular and even 

 series — without any break and without any marked pro- 

 jection of one tooth above the level of the rest ; a pecu- 

 liarity 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 Anoplo- 

 thermm. The teeth of the Gorilla, on the contrary, ex- 

 hibit 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 Go- 

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



