520 ZOOLOGY SECT. 



times well-developed, sometimes rudimentary. The tuber cal- 

 canei is an inwardly curved process of the calcaneum, attached 

 to which by means of ligamentous fibres is a slender rod of 



S>X^L/ 



FIG. 1106. Skull of Pteropus fuscus. (After Blainville.) 



bone or cartilage, the calcar, which supports the inter-femoral 

 membrane. 



Skeleton of the Primates. The atlas is ring-like, the 

 odontoid sub-conical. The spines of the cervical vertebrae are 

 usually well developed and simple : in Man they are short, with 

 the exception of the seventh, and bifid : in some they are trifid. 

 The number of thoracico-lumbar vertebrae is usually nineteen, 

 but only seventeen in Man, the Gorilla and Chimpanzee, sixteen 

 in the Orang ; in some Lemurs it may be twenty-three or 

 twenty-four. The number of sacral vertebras varies from two to five. 

 The sacral region of Man, which comprises five ankylosed vertebrae, 

 differs from that of other Primates in its greater relative breadth 

 and in its backward curvature ; it forms a well-marked angle 

 where it joins the lumbar region the sacro-vertebml angle scarcely 

 recognisable in other Mammals. The number of caudal vertebras 

 varies with the length of the tail, from four to about thirty- 

 three. In Man there are only four vestigial caudal vertebras, anky- 

 losed together to form the coccyx. In all those forms in which the 

 tail is well developed chevron bones are present. 



The human skull (Fig. 1107) presents a marked contrast in 

 certain respects to that of other Mammals, but in many points is 

 approached by that of the other Primates, more especially by that 

 of the Simiidas. One of the most important characteristics of the 

 human skull is the large size of the brain-case, the cubic content 

 of the cranial cavity averaging 1500 cubic centimetres in the male 

 of white races. This great development is most marked in that 

 part of the cavity which lodges the cerebral hemispheres, in adapta- 

 tion to the large dimensions of which the cranium bulges out both 



