536 



ZOOLOGY 



SECT. 



backward curvature ; it forms a well-marked angle where it joins 

 the lumbar region the sacro-vertebral angle scarcely recognisable 

 in other Mammals. The number of caudal vertebrae varies with 

 the length of the tail from four to about thirty-three. In Man 

 there are only four vestigial caudal vertebras, ankylosed together 

 to form the coccyx. In all those forms in which the tail is well 

 developed chevron bones are present. 



The human skull (Fig. 1188) presents a marked contrast in 

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



fa 



SO 



a 



FIG. 1188. Skull of Man. Letters as in Fig. 1167. In addition, a. angle of mandible; 

 e.g. crista galli, a process of the mesethmoid ; fm. foramen magnum ; M. mastoid; 

 st. sella turcica. (After Flower.) 



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

 of the Simiidae. 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 

 anteriorly and posteriorly to such an extent that the entire length 

 of the cavity greatly exceeds that of the basi-cranial axis. A 



