OCR Text |
Show 1899.] DR. A. KEITH ON THE CHLMJ?XNZ£ES. 303 enough of material to make any statement as to their development in Anthropjopithecus calvus and A. kooloo-kamba. The premolars of the Chimpanzee although differing in size, do not differ much in the number and arrangement of their cusps. The canine teeth have attained their greatest development amongst the large Anthropoids in the Gorilla. Their large size expresses the ferocity of the animal. The sexual difference between the canines of the male and female is much greater in the Gorilla than in the Chimpanzee: the canines of the male Chimpanzee equal in their development those of the female Gorilla. The upper canines of the male Gorilla project 14-15 m m . above the other teeth; their antero-posterior diameter varies from 1S-20 mm.; the lower project above the premolar teeth from 8-10 m m . The development of the upper canines of the male Chimpanzee is much less than those of the Gorilla : the upper projects b-12 m m . with an antero-posterior diameter of 12-15 mm.; the lower reaches above the other teeth from 4-6 m m . In the female Gorilla the upper canines reach above the other teeth from 8-10 mm.; the corresponding measurement in the Chimpanzee is from 6-8 mm.: in the lower teeth, the canines of the Gordla project 4-6 m m . : in the Chimpanzee seldom more than 3 m m . The size of the canine teeth helps in the diagnosis of the Chimpanzee. The incisor teeth of the Gorilla are a fourth larger than those of the Chimpanzee, but the relatiA"e size of the individual incisors is almost the same. The upper lateral incisors, owing to the great size of the canines, are relatively small in the Gorilla. The arrangement of the cuspules of enamel on the teeth of the one is different from that of the other, but the small amount of material at m y disposal precludes me from making any more definite statement. In both the Chimpanzee and Gorilla the last permanent and canine teeth commonly cut together; but in the Chimpanzee the canine cuts more frequently before the last molar than in the Gorilla. " Johanna'"' has the habit of yawning frequently, when a full view is got of her teeth, and there cannot be a doubt for an instant that in every point she possesses the dentition of a female Chimpanzee. I know of four instances of supernumerary molars in the Gorilla. I know of only one in the Chimpanzee, and yet Chimpanzee skulls are three times more numerous than those of the Gorilla. 6. The Myologkal and Osteologieal Differences in the Bodies and Limbs of the Gorilla and Chimpanzee. It is a very remarkable fact, and one that very forcibly proves the close relationship betAveen the Gorilla and Chimpanzee, that there is scarcely a feature in any muscle or bone found in one animal which is not also found in the other. "What is the exception in the one, frequently proves the rule in the other, and |