A Hand-book to the Primates, Volume 2 (of 2)

by Henry O. Forbes

"The Orangs come nearest to Man in the number of the ribs, the form of the cerebral hemispheres, the diminution of the occipito-temporal sulcus [groove] of the brain, and the ossified styloid process; but they differ from him much more widely in other respects, and especially in the limbs, than the Gorilla and the Chimpanzee do.

"The Gorilla is more Man-like in the proportions of the leg to the body, and of the foot to the hand; further, in the size of the heel, the curvature of the spine, the form of the pelvis, and the absolute capacity of the cranium.

"The Chimpanzee approaches Man most closely in the character of its cranium, its dentition, and the proportional size of the arms." (Huxley.)

THE HUMAN RACE. FAMILY HOMINIDÆ.

With this family we reach the culminating point of the zoological tree. It contains but one monotypic genus, Homo, with its single species, Homo sapiens. Although deriving his specific designation from the unique characteristic of his mental attributes, Man comes under review here alone in his physical aspect as one of the mammalian animals.

"Identical in the physical processes by which he originates—identical in the early stages of his formation—identical in the mode of his nutrition before and after birth, with the animals which lie immediately below him on the scale—Man, if his adult and perfect stature be compared with theirs, exhibits, as might be expected, a marvellous likeness of organisation. He resembles them as they resemble one another—he differs from them as they differ from one another." (Huxley.) On comparing his external form and internal organisation with that of all the other known zoological forms, he is found to fit no niche in the scale of classification, founded on the same principles of likeness and dissimilitude as applied to them, except in the vicinity of the Gibbons, the Orangs, the Gorillas, and the Chimpanzees, of whose order—the Primates—he forms only an additional though higher Family, solely on his structural characters and entirely apart from those intangible mental attributes which remove him supremely above all other creatures. Unbridged as is the chasm between the Ape and Man, "the structural differences which separate Man from the Gorilla and the Chimpanzee, are not so great as those which separate the greater from the lower Apes." (Huxley.)

Of the three higher Apes, the Chimpanzees are those which appear to approach Man most closely; but he is distinguished from them and from all the other members of the Simiidæ by his body being supported in the erect position upon the outer edge of a broad, arched, short-toed foot, articulated at right angles to the leg. This foot has a prominent heel and a stout great-toe, longer than all the digits, except the second, but lying parallel and not opposable to them, or capable of being moved away from them, because of the flat unrounded articular surface of the ento-cuneiform bone of the ankle. His back-bone has a strongly-marked, open S-shaped curvature, with its concavity in the lower back, giving it its elasticity and breaking any shock which might be transmitted otherwise to the brain through the jolt of walking in the vertical position. His arms are proportionately much shorter than the legs, and also the spine; the thumb is also longer in proportion than in the Apes, and, as the fingers have all separate movements, the hand is thus better able to be adjusted to minute operations. The head in Man is equipoised on the vertebral column just under the centre of its mass, and is thus easily supported and moved, whereas, in all lower forms of Vertebrates, it is placed further and further from the centre towards the back, with its weight thrown towards the front. In Man the skull cavity, not intruded upon and diminished by the roof of the orbits, is characteristically high and arched, its capacity being twice as great as any Ape's; still the difference in the cranial capacity of different races of Man is much greater absolutely than that between the highest Ape and the lowest Man. (Huxley.) His facial and jaw-bones are smaller, and project far less, even in the most prognathous of men, than in the Apes; the lower front margin of the under jaw is characteristically human, being produced forward to form the chin. In the human skull there is always a spike-like bone—the styloid process—dependent from and ossified to the ear-bones.

In Man the form of the pelvis—the large osseous block to which the legs are articulated—is very characteristic in its width; its great basin-shaped cavity receives and supports his lower internal organs; to its extensive external surface the muscles for enabling him to retain the erect position are attached, while its width, by separating the thigh-bones, gives to the body a form favourable to stability, which is increased by the wide angle at which the articulating head of the femur is attached to its shaft. "Were he to desire it, Man could not, with convenience, walk on all fours: his short and nearly inflexible foot, and his long thigh, would bring the knee to the ground; his widely separated shoulders and his arms, too far extended from the median line, would ill support the fore-part of his body; the great indented muscle which, in quadrupeds, suspends the trunk between the blade-bones as a girth, is smaller in Man than in any one among them; the head is heavier, on account of the magnitude of the brain, and the smallness of the sinuses or cavities of its bones; and yet the means of supporting it are weaker, for he has neither cervical ligament, nor are the vertebræ so modified as to prevent their flexure forward; he could, therefore, only maintain his head in the same line with the spine, and then, his eyes and mouth being directed towards the ground, he could not see before him." (Cuvier.)

The breadth of the sacrum is equal to or exceeds its length, and the width of the pelvis exceeds its height, the reverse of what is seen in Apes. The wrist (carpus) in Man has no central bone; the ankle (tarsus) is longer than the metatarsal segment, and that is again longer than the toe-bones, which are more compressed than the finger-bones. In Man the teeth form a continuous series—there is no diastema, which, with the exception of the extinct Anoplotherium, is alone true of Man; his canine teeth are never prominent or tusk-like.

The human brain differs from that of the Man-like Apes in regard to its convolutions and their separating grooves, only in minor characters; but in weight, as in capacity, very greatly. The weight of a healthy full-grown human brain never descends below thirty-two ounces, that of the largest Gorilla, far heavier than any Man, never attains to more than twenty. Yet, "the difference in weight of brain between the highest and the lowest Men is far greater relatively and absolutely than between the lowest Man and the highest Ape." (Huxley.)