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Show 300 DR. A. KEITH ON THE CHIMPANZEES. [Mar. 7, greater body-weight of the former K 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 D u Chaillu measures 420 c.c, rather more than the average capacity of the male Chimpanzee ; four skulls of males brought by Emin Basha 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 ; tAvo females averaged 368 c.c. These figures, so far as they go, shoAv 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 Avhole 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 m m . 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 difference between the females Avas 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. 1 DUBOIS, E. " Ueber die Abhangigkeit des Hirngewichtes von der Korper-grosse beim Menschen," Archiv fur Anthrop. 1898, Bd. xxv. p. 423. |