AND AFFINITIES OF THE GORILLA. 



'^57 



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 vertebrae in Man, and 

 only so called when they become long and free. The genera Homo, Troglodytes, and 

 Pithecus have precisely the same number of vertebrae : 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 vertebrae, 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 aflinity 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 Linnaeus. 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 at issue. It is 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 (PI. 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 

 afiinity 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 j the proportional size of the 

 condyloid and petrous processes; the mastoid processes, which relate to balancing the 



