THE SPINOUS PROCESSES 113 



one hand-grasp only to gain another. It is in this fashion 

 that human performers on the high trapeze pass from 

 one swinging bar to another. 



It is this factor, a purely arboreal one, that has led to 

 the typical condition of the anthropoid vertebral column, 

 and determined the disposition of its muscles and the 

 arrangement of its bony prominences. The springing 

 point in the middle of the backbone is absent, and the 

 column acts as a whole; its spines are in uniform series, 

 and its accompanying muscles support it as a pillar, 

 rather than bend it as a spring. 



There is nothing in this that is peculiar to Man, nothing 

 that has any relation to the attainment of any distinctive 

 human attribute; it w^as among the branches, as an 

 outcome of the arboreal life, that the uniformly sloping 

 series of spinous processes, seen in the human vertebral 

 column, was attained. 



Among the Anthropoids themselves some minor varia- 

 tions are seen in the disposition of the sj)inous processes. 

 In the Gibbons the series is quite uniform, but in the 

 large Anthropoids the spines in the cervical region are 

 peculiarly elongated. More than this, in the Gorilla the 

 spine of the third cervical vertebra is strongly ant everted, 

 and at times the fourth and fifth share in a slight forward 

 slope. Again, at the hind end of the series some varia- 

 bility is seen, for some of the posterior spines are not 

 distinctly retroverted. In Man this variability in the 

 posterior spines is also present, for the lumbar spinous 

 processes do not always slope in quite the same manner. 

 In some primitive human races there is even a tendency 

 to anteversion in the jDOsterior spines, which shows itself 

 at times quite distinctly in the first sacral vertebra. 



8 



