300 DR. A. KEITH ON THE CHIMPANZEES. [Mar. 7, 



greater body- weight of the former i. The weight of " Johanna " 

 is 140 lbs. The greater cranial capacity of the Gorilla is marked 

 before the end of the milk-dentition. 



Cranial capacity does not help us to distinguish between the 

 various forms of Chimpanzee. The skull of a male " Kooloo-kamba " 

 brought home by Du Chaillu measures 420 c.c, rather more than 

 the average capacity of the male Chimpanzee ; four skulls of males 

 brought by Emin Pasha from Central Africa average 422 c.c. ; two 

 females measured 378 c.c, showing distinctly a high average, and 

 confirm in some degree the supposition that the Central-African 

 form is a distinct variety : a male of the variety known as A. calvus 

 measured 420 c.c. ; two females averaged 368 c.c. These figures, so 

 far as they go, show that the Chimpanzee, although widely spread, 

 has not broken up into forms separated widely by a divergence in 

 brain size. 



5. The Palate and Dentition of Gorillas and Chimpanzees. 



The size and shape of the hard palate, counting as the palate 

 the whole area lying with the outer margin of the dental arcade, 

 seem to me of great importance. The size and shape of the 

 palate express better than other features the brute development 

 of the race. The larger the relative size of the brain, the smaller 

 the relative development of the palate. Its size and shape depend 

 on the degree of development of the teeth. In an animal like the 

 Gorilla, in which the dentition is complete and robust, the palate is 

 extremely large and its length is much greater than its breadth. 

 In the Chimpanzee at birth the breadth of the palate, as in Man, 

 is greater than its length, whereas in the Gorilla the length is, 

 even at birth, greater than the breadth. The development of the 

 facial parts of the skull and of its bony crests depends on the size 

 and shape of the palate. 



As in the case of the cranial capacity, the palatal differences of 

 the male Gorilla and Chimpanzee are very marked. The average 

 palatal area of seven adult male Gorillas was 7200 mm. ; the breadth 

 was 63 per cent, of the length : the corresponding figures in 15 

 adult male Chimpanzees were, palatal area 4580 mm. and the breadth 

 was 77 per cent, of the length. The maximum measurements in 

 the Chimpanzees were less than the minimum measurements of the 

 Gorillas. But the difiference between the females was less marked ; 

 the palates of some Chimpanzees exceeded those of some Gorillas. 

 Here, again, the palate affords no certain index as to the animal. 

 But, on an average, the palate of the female Gorilla is much 

 the larger : for 7 adult female Gorillas it was found to measure 

 5600 mm., the breadth being 73 per cent, of the length ; in 

 11 female Chimpanzees the average area was 4200 mm., and the 

 breadth 77 per cent, of the length. The figures quite bear out my 

 opening statement that the brute development of the Gorilla, even 

 in the female, is much greater than in the Chimpanzee. 



^ Dubois, E. " Ueber die Abhangigkeit des Hirngewichtes von der Korper- 

 grosse beim Menschen," Archiv fiir Anthrop. 1898, Bd. xsv. p. 423. 



