The ilia are much longer, thicker, more massive, and narrower, and present no central transparent portion nor internal fossa, being flat anteriorly and concave posteriorly, the re verse of the human ilia, and looking almost directly backwards and forwards, and very little inwards and upwards ; so that, in these animals, there cannot be said to be any false pelvic cavity. In the Uran of the Hunterian Mu seum they are two thirds of the femurs in length, and measure 6 inches, and in the Chimpanzee 7 inches, reaching as high as the third lumbar vertebra. From the limited expansion of the wings, the anterior part *seems deficient, the anterior superior spine (a) being placed directly over the cotyloid cavity ; and the crest (c) being, consequently, very short, terminating abruptly at the vertical rib mentioned in the description of the human ilium. The (Ike are more expanded in the Uran than the Chimpanzee. The crest does not present the lateral f-like curvature, and is less arched than in man. The anterior iliac spines are more widely separated, the inferior (b) being scarcely discernible, and the border between them thin and concave. The posterior, or iliac tuberosity is even less prominent in these animals than in the lower order of Ruminants. The distance from the cotyloid to the sacro iliac joint is at inches in the Hunterian Chim panzee, and about 3 inches in the Uran, though, from the greater straightness and obliquity of the cotylo-sacral arch (d) and the want of the anterior curve, the direct horizontal distance between these points is about the same as in man.
In the Sintice generally, the ilia are said to be placed almost in a straight line with the spinal column. Added to the great length of the ilia, this arrangement causes the pelvic brim to be much elongated from before back wards ; but much less so, however, than it would be if the pubes and iliac shafts were in the same plane. I have, however, found the ilio-vertebral angle in Chimpanzee, Uran, long armed Gibbon, and brown Baboon to be very little, if at all greater than the human pelvi vertebral, as far as could be ascertained without actual section of the bones. But in the Lemurs the ilia are only 10° from being in the same straight line with the spine ; while in the Man drill and many Monkeys they are almost pa rallel. This characteristic, heightened by that of the much diminished curve of the lumbar vertebra and the elongation of the iliac shafts in these animals, contributes to form a great contrast with those of the human pelvis. In the Uran, a projection of the sacro-iliae joint in front is observable, and a solidity of the shafts of the ilia. Blainville remarks, that the sacro iliac facet is oval in these animals.
The ischia, in common with the whole pelvis, are longer in the Chimpanzee than in the Uran ; and the ischial tuberosities (e) more turned outwards. In both, however, they are
directed much more in the line of the ilia than in the human species, the ilio-ischial angle being 165° ; and are larger, more flattened, spread, and diverging. The ischial spines in these animals begin to degenerate, and are rather rounded eminences or ridges than true spines; and the inferior rami (f) are directed almost horizontally inwards, leaving a large triangular foramen obturatorium, and entering into the formation of the pubic symphysis (g), which in the Siznice generally, may be more properly called the ischio-pubic symphysis. The whole of the ischial portion of the pelvis has a more anterior position, and a more laterally flattened appearance than in the human pelvis. The cotyloid cavities are small, elongated ver tically, and deeper behind than above. The sciatic notches are long and narrow.
One of the most remarkable differences from the human pelvis, however, is the dfference of direction of the ilia and pubes with regard to the transverse-vertical plane of the spinal column, an arrangement which bends the plane of the pelvic brim at the ilio-pectineal eminence in different directions. In the Chimpanzee, the antero-posterior angle, formed by the su perior reruns of the pubis with the cotylo sacral arch of the ilium, is 120°, and in the Uran 125° ; constituting a striking difference from the human pelvis, where the cotylo-sacral and pubic arches are in one plane.
This alteration in the direction of the pubis will be found to be a great characteristic of all quadrupeds, in the prone position of whose bodies the pubis has a tendency to be placed more vertical and more antenor, to be out of the way of the femurs in their angular movements. In the Sloths and Anteaters, the pubis will be seen to be turned in the opposite direction, yet still forming an angle with the iliurn, but with the retiring sides turned backwards. I think, therefore, we may safely take the ilio-pubic angle as a general peculiarity of the inferior animals possessing pelves, and one which distinguishes them, as far as I hare seen, universally, from the human species (see page 173. fig. 112. 2 —13.).
A remarkable consequence of this more horizontal direction of the:pubis in the Sinzice is the disappearance of the angle of the symphysis, it being quite parallel with the spinal column. And this parallel position is, according to Cu vier, a mark of distinction between all the brute creation and man. In other respects, the pubis of the Simice is short, little arched, and without marked spine. The inferior outlet of the pelvis is larger than it would otherwise be, from the elevation of the coccyx, and, from the shortness of the sacrum, and length of the ischio-pubic symphysis, its plane is more parallel, and its axis more in a line with those of the brim than in man.