THE BONES 



67 



(except in the dugong). Man, on the other hand, has invari- 

 ably 7 cervical, 12 dorsal (very rarely 13), 5 lumbar, 5 composing 

 the sacrum, 4 (very rarely 5) united in the coccyx. The human 

 vertebral column resembles most closely that of the anthropoids. 

 In the orang, gorilla, and chimpanzee, the 

 normal number of thoracic-lumbar vertebrae 

 is 1 6, in the hylobates 18. 



In exceptional cases the fifth lumbar verte- 

 bra is converted into the first sacral. According 

 to the relative number of his vertebrae, man 

 occupies an intermediate position between the 

 hylobates and the other anthropoids. 1 Peculiar 

 to man is the double S-shaped curve of the 

 spine ; according to Cunningham and Huxley 

 there are faint signs of it in the gorilla, but it 

 is entirely absent in all other anthropoids, even 

 in an erect attitude. ( 



In all mammals the dorsal and lumbar 

 vertebrae are ventrally concave, and in Euro- 

 pean children and the lower races of man (e.g., 

 the Veddahs), the lumbar vertebrae at least are 

 ventrally concave. In the adult of the higher 

 races it is the S-shaped curve which gives the 

 spine its elasticity and enables it to maintain 

 an erect position. 2 



This divergence from the original type of 

 the Primates is, according to Klaatsch, due to 

 the fact of the lumbar vertebrae being sharply 

 curved against the sacrum, this being caused by 

 the repeated backward pressure of the sacrum FlG 

 in climbing high trees, after the manner of 

 existing wild tribes. Through the peculiar 

 curve of the lumbar spine thus attained, the 

 weight of the head and of the upper part of 

 the trunk was directed so far to the back as to establish the 

 balance necessary for the erect position. On this head the 

 apes may be divided into two groups : the lower apes having 

 the same curve as all other quadrupeds, and the anthropoids in 



J C. Gegenbauer, lac. cit., i , 175. 2 Ranke, loc. cit., i., 351. 



5* 



21. Human 

 vertebral col- 

 umn in erect 

 position viewed 

 from the right 

 side. (H. 

 Meyer.) 



