THE CHIMPANZEES AND ORANGS. 91 



canal, from which hole a canal is continued downwards and forwards. The hole is in 

 the middle of the ascending ramus. 



Compared with the mandible of the Human species, even of the lowest variety, the 

 Austrahan, e.g. (PI. XXXI. figs. 2 & 3), the first and chief distinction is the absence 

 of the chin, a feature which is as well marked in the black as in the white races of the 

 Human kind. The entire jaw is much shorter in proportion to the intercondyloid space, in 

 Man ; for the distance between the condyles is as great in most adult male jaws as in the 

 Gorilla, and in some it is greater ; whilst the ordinary length of the lower jaw, in a straight 

 line from the back part of the condyle to the fore part of the symphysis, is from 4^ to 

 5 inches. The angle of the jaw is usually more rounded off in the Australians, as is 

 shown in fig. 2, than in Europeans ; but is always less rounded and better marked than 

 in the Gorilla. The parabolic or elliptic curve of the alveolar arch (fig. 3), the pro- 

 gressively diminishing size of the sockets from the molars to the incisors, and the thin 

 sharp wall between each alveolus, are also well-marked characteristics of the human jaw 

 in this comparison. 



Of the generally developed vertical ridge or ' tuber maxillare ' at the lower and fore 

 part of the symphysis in the human jaw, there is no trace in the Gorilla ; and the 

 tubercles, sometimes developed in a transverse pair, or three in number, at the back sur- 

 face of the symphysis, are equally wanting in the Gorilla. The outer surface of the jaw, 

 beneath the outer and anterior origin of the ascending ramus, is more protuberant in Man. 

 As to the ' external oblique ridge ' attributed by some Anthropotomists as a normal 

 character to the Human lower jaw, the very frequent absence of any such ridge in Man 

 renders the like absence in the jaw of the Gorilla of little moment in this comparison. 



The foramen mentale, which is below the first premolar in the Gorilla, is usually below 

 the second premolar in Man, as it is also in the Chimpanzee and Orang. The inner and 

 anterior ridge of the ascending ramus converges more regularly or directly as it ascends 

 to the outer one in Man, and has not the angular deflection which it shows in the 

 Gorilla. The ridge which extends from that angle to the condyle in the Gorilla, above 

 the foramen dentale, is more feebly marked, or is wanting, in Man. The horizontal 

 ramus gradually and slightly diminishes in vertical extent as it approaches the ascend- 

 ing ramus : the contrary is the case in the Gorilla. The thickest and most prominent 

 part of the condyle is nearest the middle of that joint in Man. The point of the 

 coronoid is on the same vertical line with the fore part of the base of the ascending 

 ramus : in the Gorilla it is bent more backwards. The interval between the coronoid 

 and condyloid processes is relatively wider and more shallow in man. 



The inner wall of the molar alveoli overhangs the subjacent part of the jaw more 

 abruptly in Man than in the Gorilla: the frequent development of the (internal 

 oblique) ridge extending from behind the socket of the last molar forwards and downwards 

 to beneath the first molar, or a little further, is a characteristic of the human jaw as 

 compared with that of the Gorilla and other Anthropoid Apes. There is only a 



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