Aeby observes that the bodies of the vertebræ are tapering in the gorilla, and this is, in fact, the case. In climbing, or when he goes on all fours, the dorsal curvature of an anthropoid maintains its position. This curvature is still more apparent when the animal, in climbing, withdraws his body from the tree, mast, or whatever it may be, and bends forward his head. A similar dorsal curvature of the vertebral column may be observed in men who stiffen their hands and feet to climb up a tree or mast. If an anthropoid holds himself so erect as to be able to place his hands behind his head, the dorsal curvature of his spine is necessarily straightened, and indeed it becomes rather a ventral curvature. The bony pelvis of anthropoids, with its high, narrow, and projecting ilia, and the lowest lumbar vertebræ deeply embedded between them, together with the sacral and coccygeal vertebræ, which directly remind us of the vertebræ of a rudimentary tail, present the points of unlikeness with the human skeleton in this part of the skeleton of these animals in the strongest light (comp. Figs. 40 and 41). The bony thorax of anthropoids is distinguished from the human thorax in normal cases by the abrupt way in which it widens outwards. The thorax of the gorilla, and the widely diverging pelvic bones, which enclose the belly and give it a tun-shaped form, contrast with the graceful moulding of the corresponding parts of the human form. Certain peculiarities in the structure of the bones of the shoulder-girdle and of the extremities of anthropoids, in which they differ from corresponding parts in the human structure, have been already mentioned. With reference to the humerus of the gorilla, Aeby asserts that the head of the bone forms a cycloid, placed transversely, while in man its shape is that of the segment of a sphere. But I have pointed out in my treatise on the gorilla that there is a not inconsiderable variation in the form of the head of the humerus in these animals, and it is sometimes cycloidal or vertically-cycloidal, sometimes a segment of a true sphere. In the chimpanzee, orang, and gibbon this part of the humerus is always a segment of a sphere, while in man its form is not equally invariable. Aeby further observes that the transverse-cycloidal form of the head of the humerus in the gorilla justifies the inference that this animal, in the use of its fore-limbs, is accustomed to turn them transversely on their axis. But the direct observation of a living anthropoid, as well as the examination of its dead body, make it clear that the action of the ball and socket is remarkably free, and this theoretical surmise is contradicted by the perfection of the natural mechanism. [Illustration: