THE CHIMPANZEES AND ORANGS. 13 
The crest of the ilium (Pl. VI. fig. 1, a,e) describes a portion of a curve of a much 
larger circle than that described by the same part in Man (fig. 4, a, e, c); but the 
crest of the ilium of the Chimpanzee (fig. 3, a, e) is less curved than in the Gorilla. 
In the full-grown but young male Gorilla, the ilium, with the whole breadth in view, 
presented the regular curve of the crista, as shown in fig. 1, Pl. VI.: but in the old 
male subsequently acquired (PI. XII. fig. 2), the stimulus of the exercise of the power- 
ful muscles had led to the prominence of the crest at the part where the origin of 
the latissimus dorsi terminates outwardly by the strongest part of its tendinous sheath. 
The line of the anterior border (a to 8, fig. 1, Pl. VI.) is more angular in the young 
and more regularly curved in the old male (Pls. XII. & XIII. fig. 2); in neither is the 
process (called ‘ antero-inferior spine’ in Anthropotomy) for the origin by its straight 
tendon of the rectus femoris muscle developed as in Man (PI. VI. fig. 4,)). This 
muscle has an important share in maintaining the erect position, and is, proportionally, 
much more developed in Man, than in the Gorilla and other Apes. In like manner the 
backward development of the ilium in Man, as from e to ¢, fig. 4, favouring the origin 
of the gluteus maximus, is wanting in the Gorilla,—a comparatively small proportion 
of the outer surface of the bone being applied to the attachment of the more feeble 
gluteus, which, by its inferior breadth and thickness, loses all title to the term ‘ maximus ’ 
in Apes. The inequalities on the outer surface, indicating the origins of the gluteus 
medius and gluteus minimus in Man, are less marked in the ilium of the Gorilla. 
From the arrest of the backward development of the ilium in the Gorilla, the great 
sacro-sciatic notch (Pl. VI. fig. 1, f) is much less deep than in Man (ib. fig. 4, f) ; but 
it is deeper in the Gorilla than in the Chimpanzee (ib. fig. 3, f). 
The anterior surface of the ilium (Pl. XII. fig. 4) presents a smooth and slight 
equable concavity for the iliacus internus muscle, and a narrower but longer articular 
surface for the sacrum, which includes one, and in old subjects two vertebra (ib. + & 5) 
homologous with the lower lumbar vertebre in Man. Through this consequence of 
the elongation of the iliac bone, and the development of the ribs of the vertebra 
answering to the first ‘lumbar’ in Man, the number of vertebre retaining the anthropo- 
tomical characters of ‘ lumbar’ ones becomes reduced to two in the Gorilla (ib. 2, 3), which 
greatly diminishes the flexibility of the massive trunk in that animal. The weight of the 
trunk at the same time requires that increased extent of grasp of the spine by the ossa 
innominata, afforded by the superadded sacrals, by means of which the superincumbent 
weight is received and adequately transferred by the pelvis to the lower limbs, when 
the animal assumes the erect posture. From this character of the spine and pelvis I 
inferred a more frequent assumption and easier maintenance of the erect or bipedal 
posture by the Gorilla, which Mr. du Chaillu’s subsequent observation of the animal in 
his native haunts! has shown to be one of its distinctions from the Chimpanzee. 
The ascending part of the ischium, called the ‘ ramus,’ is not only longer, but is 
broader and thicker in the Gorilla (Pl. VI. A, ), than in Man, and the tuberosity (ib. /) is 
» Op. cit. 
