804 TEETH OF ORANG AND CHIMPANZEE. 



panzee. The repetition of the strong sigmoid curves, 

 which the unworn prominences of the first and second 

 true moj^rs present in man, is a very significant indica- 

 tion of the near affinity of the gorilla and the chimpanzee, 

 as compared with the approach made by the orangs or 

 any of the inferior quadnimana, in which the four cusps 

 of the true molars rise distinct and independently of each 

 other. The premolars as well as molars are severally im- 

 planted by one internal and two external fangs, diverging, 

 but curving towards each other at their ends as if grasp- 

 ing the substance of the jaw. In no variety of the human 

 species are the premolars normally implanted by three 

 fangs ; at most the root is bifid, and the outer and inner 

 divisions of the root are commonly connate. It is only 

 in the black varieties, and more particularly that race in- 

 habiting Australia, that I have found the wisdom tooth, 

 or last true molar, with three fangs as a general rule ; and 

 the two outer ones are more or less confluent. 



The molar series in both species of chimpanzee forms 

 a straight line, with a slight tendency in the upper jaw to 

 bend in the opposite direction to the well-marked curve 

 which the same series describes in the human subject. 

 This difference of arrangement, with the more complex 

 implantation of the premolars, the proportionally larger 

 size of the incisors as compared with the molars ; the still 

 greater relative magnitude of the canines ; and, above all, 

 the sexual distinction in that respect illustrated by the 

 skull of the full-grown male gorilla (Fig. 50, p. 223), 

 stamp the chimpanzees most decisively with not merely 

 specific but generic distinctive characters as compared 

 with man. For the teeth are fashioned in their shape 

 and proportions in the dark recesses of their closed 

 formative alveoli, and do not come into the sphere of ope- 



