THE ERECT POSITION IN MAN. 225 



the vertebral column is vertical. No animal form of vertebral 

 column can be elevated into the perpendicular position. In 

 apes, in the so-called upright position, the axis is oblique ; 

 and when these animals are on all fours, nearly horizontal. 

 In birds, also, it is oblique. In quadrupeds, horizontal. 



b. In no animal form of vertebral column is the column 

 itself cut by its own axis in five points as in the human 

 column. In no animal does it pass through a greater num- 

 ber than four. The axis of the human spine is therefore 

 peculiar in passing across it so frequently. 



c. In no form of animal vertebral column are the second- 

 ary curvatures so highly developed as in the human, and no 

 animal possesses the lumbar curvature. As the development 

 of the foetus advances, the spine loses its primary embryonic 

 curve and becomes straight, excepting a slight bend at the 

 coccyx : this is the case even in the child at birth. The 

 curves which appear in the human spine after birth are new or 

 secondary curves. The corkscrew curve of the tail of the 

 spider-monkey is probably an original elementary curve. In 

 the human spine, the neck is convex forward, the dorsal region 

 convex backward ; lumbar forwards, sacro-coccygeal backwards. 

 There is also a series of lateral curvatures — dorsal region con- 

 vex to right, cervical and lumbar to left, sacro-coccygeal to right. 

 If the lateral and antero-posterior curves are connected to- 

 gether, they resolve themselves into a corkscrew-like curve ; 

 not the curve of a thread running regularly round a cylinder, 

 but arranged so as to increase or diminish in their course. 

 In disease these curves increase ; dorsal to right, cervical to 

 left, lumbar to left, sacro-coccygeal to right. The anterior 

 faces of the bodies of the vertebrae in the dorsal and sacro- 

 coccygeal regions, are consequently inclined to the right; in the 

 lumbar and cervical to the left. No animal has such a spiral 

 development as the above. In fish, the only trace of the fun- 

 damental curve is the tnrn-np <>(' the tail, and probably some 



