46 HUMAN PHYSIOLOGY. 



usual oblique position of that bone ; so that by this arrangement, the whole 

 weight- of the body, in its erect posture, falls vertically on the top of the tibia, 

 when the joint is in the firmest position in which it can be placed. The knee- 

 joint of the Orang, on the other hand, is comparatively deficient in extent of 

 articulating surface ; and its whole conformation indicates that it is not intended 

 to serve as more than a partial support. The Human foot is, in proportion to 

 the size of the whole body, larger, broader, and stronger, than that of any other 

 Mammal save the Kangaroo. Its plane is directed at right angles to that of the 

 leg ; and its sole is concave, so that the weight of the body falls on the summit 

 of an arch, of which the os calcis and the metatarsal bones form the two points 

 of support. This arched form of the foot, and the natural contact of the os 

 calcis with the ground, are peculiar to Man alone. All the Apes have the os 

 calcis small, straight, and more or less raised from the ground ; which they 

 touch, when standing erect, with the outer side only of the foot : whilst in 

 animals more remote from Man, the os calcis is brought still more into the line 

 of the tibia ; and the foot being more elongated and narrowed, only the extremi- 

 ties of the toes come in contact with the ground. Hence Man is the only species 

 of Mammal which can stand upon one leg. All the points in which the feet of 

 the anthropoid Apes differ from his, are such as assimilate them to the manual 

 type of conformation, and enable them to serve as more efficient prehensile 

 organs ; whilst they diminish their capacity to sustain the weight of the body, 

 when it simply rests upon them. 



6. There is a considerable difference in the form of the trunk, between Man 

 and most other Mammalia ; for his thorax is expanded laterally, and flattened 

 in front, so as to prevent the centre of gravity from being carried too far for- 

 wards ; and his sternum is short and broad. Between the bony walls of the 

 thorax and the margin of the pelvis, a considerable space intervenes, which is 

 occupied solely by muscles and tegmnentary membranes ; and these would be 

 quite insufficient to sustain the weight of the viscera, if the habitual position of 

 the trunk had been horizontal. In these particulars, however, the most anthro- 

 poid Apes agree more or less completely with Man. 



7. Returning now to the skull for a more minute examination, we observe 

 that the cranium of Man is distinguished from that of the anthropoid Apes, not 

 merely by its great capacity, but also by its smoothness ; its surface being 

 almost entirely deficient in those ridges for the attachment of muscles, which 

 are remarkably strong both in the Chimpanzee and Orang, and which impart 

 to its configuration somewhat of a carnivorous character. This aspect is strength- 

 ened by the great depth of the temporal fossa, and by the extent and strength 

 of the zygomatic arch; features that are most remarkably developed in the 

 Troglodytes gorilla, a newly-discovered species of Chimpanzee, which is regarded 

 by Prof. Owen as presenting on the whole the nearest approach to the human 

 type. Moreover, the jaws in even the most degraded races of Man project far 

 less from the general plane of the face, than they do in the Apes ; and his teeth 

 are arranged in a continuous series, without any hiatus or any considerable dif- 

 ference in length, whilst all the Apes, in their adult state at least, are furnished 

 with canine teeth of extraordinary length, between the sockets of which and 

 those of the adjoining teeth (in front in the upper jaw, and behind in the lower), 

 there is a vacant space or diastenia. Even in the most prognathous Human 

 skulls, moreover, the incisors meet each other much more nearly in the same 

 axis than they do in the anthropoid Apes, in which they form an angle with 

 each other that is not nearly so divergent. The fusion of the intermaxillary or 

 premaxillary bones with the superior maxillary, at an early period of foetal life, 

 is a remarkable character of the Human cranium, as distinguishing it from that 

 of the Apes, in which the intermaxillary bones remain separate to a much later 

 period; sometimes differing also, in a very marked degree, in size and shape. 



