THE CHIMPANZEES AND ORANGS. 13 



The crest of the ilium (PI. 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, PI. 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 tendmous sheath. 

 The line of the anterior border (a to b, fig. 1, PI. VI.) is more angular in the young 

 and more regularly curved in the old male (Pis. 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, 6). 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 c, 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 (PI. VI. fig. 1,/) is much less deep than in Man {ib. fig. 4,/) ; but 

 it is deeper in the Gorilla than in the Chimpanzee {ib. fig. 3,/). 



The anterior surface of the ilium (PI. XII. fig. 2) 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 vertebrae {ib. * & ») 

 homologous with the lower lumbar vertebrae 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 vertebrae 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 

 interred 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 (PI. VI. h, I), than in Man, and the tuberosity (ib. /) is 



' Op. cit. 



