The lower extremities of Man are remark able for their length, which is proportionally greater than that which we find in any other mammalia, excepting the kangaroo and a few other leaping animals. The chief difference in their proportional length, between man and the semi-erect apes, is seen in the thigh ; and froM the relative length of this part in him, and the comparative shortness of his anterior extremities, it happens that the hands of Man, when he is standing erect, only reach to the middle of his thighs, whilst in the Chimpanzee they hang on a level with the knees, and in the Orang they descend to the ancles. The human femur is distinguished by its form and position, as well as by its length. The obli quity of its neck still further increases the: breadth of the hips ; whilst it causes the lower extremities of the femora to be some what obliquely directed towards each other, so that the knees are brought more nearly into the line of the axis of the body. This arrangement is of the greatest importance in facilitating the purely biped progression of Man, in which the entire weight of the body must be alternately supported upon each limb; for if the knees had been kept further apart, the whole body must have been swung from side to side at each step, so as to bring the centre of gravity over each tibia, — as is seen, to a certain extent, in the female sex, whose walk, owing to the greater breadth of the pelvis, and the separation between the knees, is less steady than that of the male. There is a very marked contrast between the knee-joint of Man, and that of even the high est Apes. In the former the opposed extre mities of the femur and tibia are so expanded as to present a very broad articulating sur face; and the internal condyle of the femur being the longer of the two, they are in the same horizontal plane in the 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 head of the tibia, when the joint is in the firmest posi tion in which it can be placed. The knee joint of the Orang, on the other hand, is comparatively deficient in extent of articu lating 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 existing mammal, save the kan garoo. Its plane is directed at right angles to that of the leg ; and its sole is concave, so that the whole 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 habitual 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 of the foot only ; 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 nar rowed, only the extremities of the toes come in contact with the ground. Hence Man is the only species of mammal which can stand on one leg. The points in which the feet of the anthropoid apes differ from his, all assi milate them to the manual type of conforma tion, 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.
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 pre vent the centre of gravity from being carried too far forwards. His sternum is short and broad compared with that of quadrupeds generally ; and there is consequently a con siderable space between its lower extremity and the symphysis pubis, occupied solely by muscular parts, which would be quite inade quate to sustain the weight of the viscera, if the habitual position of the trunk had been horizontal. In these particulars, however,
the most anthropoid Apes agree with Man.
Returning now to the skull for a more minute examination, and referring to the ar ticle QUADRUMANA for an account of the principal differences presented between the skulls of the ordinary Chimpanzee and ()rang, and that of Man, we shall take as our standard of comparison the recently-discovered species of Chimpanzee, designated as the Troglodytes gorilla, whose cranium is considered by Prof. Owen to approach in some respects more nearly to that of man, than do either of the preceding. This species differs from the T. niger (Simla troglodytes, Vrolik) by its con siderably greater dimensions, by the greater prominence of the supra-orbital ridges, the enormous development of the crest, which oc cupies the place of the sagittal suture, the greater strength of the zygomatic arches, and the greater size of the temporal fossa. For the more minute, but definite cha racters, on which the specific distinction is grounded, the description by Prof. Owen must be consulted.* The slightest glance at figs. 800, 801, 802. is sufficient to show how strongly marked are the features by which the skull of this Chimpanzee differs from that of even the most degraded of the Human family ; but it will be advantageous to sub join Prof. Owen's enumeration of the chief differences which are revealed by a careful anatomical survey. These are : " 1. The smaller proportional size of the cranium.
" 2. The more backward position of the foramen magnum, and its more oblique plane in relation to that of the base of the skull.
" 3. The smaller relative size, and more backward position, of the occipital condyles.
" 4. The longer basi-occipital, and broader, flatter, and lower supra-occipital.
" 5. The longer basisphenoid, and shorter alisphenoids.
" 6. The smaller size of the coalesced pa rietals, and their separation from the alisphe noids.
" 7. The conversion of a greater part of the outer surface of the parietals into con cavities or depressions for the lodgment of the temporal muscles, by reason of the bony crest developed from the line of the obliterated sagittal suture, and of the lambdoidal crest.
" 8. The larger proportion of this crest and of the squamosal plate developed from the mastoid, and the smaller size of the proper mastoid processes.
" 9. The smaller size of the vaginal and styliform processes, and the absence of the styloid process, arising from the non-anchy losis of the stylo-hyal bone.
" 10. The larger post-glenoid process, and the longer auditory process (tympanic bone), with their relative position, one behind, but not below, the other.
" 11. The position of the stronger zygo mata opposite the middle third of the basis cranii.
" 12. The prominent supra-orbital ridge.
" 13. The longer nasal bones, anchy losed together, and flattened at their lower half.
" 14. The greater proportional size, and greater prominence of the upper and lower jaws.
" 15. The longer osseous palate, and the median emarnination of its posterior border.
" 10. The parallelism of the alveoli of the molars and canine of one side, with those of the other.
" 17. The diastema, or vacant place, in front of the socket of the canine in the upper jaw, and behind that socket in the lower jaw.
" 18. The larger and more produced pre maxillaries, the persistence of more or less of their sutures, showing the intervention of their upper extremities between the nasal and maxillary bones.