ANTHROPOID APES AND MAN 



423 



erect position there come changes which are shown somewhat by the 

 semi-erect apes but which are exhibited completely only by man. One 

 of these changes is the appearance of curvatures in the spine needful 

 in the balancing of the erect body. Thus the human spine comes to 

 have a backward curvature in the thoracic and sacral regions and a 

 forward curvature in the neck and lumbar regions. A second change 

 is in the increasing development of the bodies of the vertebrae at the 

 lower end of the trunk where the weight is transmitted to the legs. 



Lateral -Fissure 



Cenfral sulcus 



Cerebellum 



Fig. 289. — Human brain from the side. From a preserved specimen. The roots of the 

 cranial nerves are indicated by roman numerals. 



With the complete emancipation of theforelimbs from any part in locomo- 

 tion and their specialization for other purposes, the pectoral girdle 

 becomes hghtened and less firmly connected to the axis of the body. 

 On the other hand the pelvis remains strongly developed, is closely 

 attached at right angles to the body axis, and is broadened for the support 

 of the viscera. The leg bones also become straighter and the great toe 

 ceases to be opposable. The foot becomes arched, which is an adaptation 

 to permit it to take up the jar due to contact with the ground, which 

 would otherwise be transmitted upward to the body. 



451. Evidences in Man of Former Arboreal Life. — There are, how- 

 ever, still evidences in man of a former arboreal condition, these being 



