AND AFFINITIES OF THE GORILLA. 257 
But Man has sometimes a thirteenth pair of ribs; and what we term “ribs” are but 
vertebral elements or appendages common to nearly all the true vertebra in Man, and 
only so called when they become long and free. The genera Homo, Troglodytes, and 
Pithecus have precisely the same number of vertebrz : if Troglodytes, by the development 
and mobility of the pleurapophyses of the twentieth vertebra from the occiput, seem to 
have an additional thoracic vertebra, it has one vertebra less in the lumbar region. So, 
if there be, as has been observed, a difference in the number of sacral vertebre, it is 
merely due to a last lumbar having coalesced with what we reckon as the first sacral 
vertebra in Man. 
The thirteen pairs of ribs, therefore, in the Gorilla and Chimpanzee are of no weight 
as against the really important characters significative of affinity with the Human type. 
But, supposing the fact of any value, how do the advocates of the superior resemblance 
of the Siamang’s or Gibbon’s skeleton to that of Man dispose of the thirteenth pair of 
ribs in the long-armed Apes ? 
In applying the characters of the skull to the determination of the important question 
at issue, those must first be ascertained by which the genus Homo trenchantly differs 
from the genus Simia of Linneus. To determine these osteal distinctions, I have 
compared the skulls of many individuals of different varieties of the Human race, together 
with those of the male, female, and young of species of Troglodytes, Pithecus, and 
Hylobates ; and I refer to the ‘ Catalogue of the Osteological Series in the Museum of 
the Royal College of Surgeons,’ 4to, 1853, for the detailed results of these comparisons. 
On the present occasion I restrict myself to a few of these results. 
The first and most obvious differential character is the globular form of the brain- 
case, and its superior relative size to the face, especially the jaws, in Man. But this, 
for the reasons already assigned, is not an instructive or decisive character, when 
comparing quadrumanous species, in reference to the question atissue. Itis exaggerated 
in the human child, owing to the acquisition of its full or nearly full size by the brain, 
before the jaws have expanded to lodge the second set of teeth. It is an anthropoid 
character in which the Quadrumana resemble Man, in proportion to the diminution of 
their general bulk. If a Gorilla with milk-teeth (Pl. XLIX. figs.3 & 4) have a some- 
what larger brain and brain-case than a Chimpanzee at the same immature age (ib. 
figs. 1 & 2), the acquisition of greater bulk by the Gorilla, and of a more formidable 
physical development of the skull, in reference to the great canines in the male, will 
give to the Chimpanzee the appearance of a more anthropoid character which really 
does not belong to it—which could be as little depended upon in a question of precise 
affinity as the like more anthropoid characters of the female as compared with the male 
Gorilla or Chimpanzee. 
Much more important and significant are the following characters of the Human 
skull:—the position and plane of the occipital foramen; the proportional size of the 
-condyloid and petrous processes ; the mastoid processes, which relate to balancing the 
