252 



ADVANCED PHYSIOLOGY 



\Cervical 



/ Dorsal 



termed the dorsal vertebrae; five heavier ones in the "small'* 

 of the back are the lumbar vertebras. 



Although the vertebrae differ in shape and size, each con- 

 sists of a rounded portion with flat 

 upper and lower surfaces, the centrum, 

 on the sides of which arise two pieces 

 of bone uniting to form the neural arch ; 

 where these two projections are joined, 

 they are prolonged into a spine, the 

 neural process; Figs. 122 and 123. 

 When the vertebra are placed on top 

 of each other, with the spines pointing 

 backward, the arches are brought over 

 each other and the openings in the 

 successive vertebra, i.e. the neural 

 foramina, together form a long tube 

 just in front of the row of spines. This 

 tube, completely surrounded by bone, 

 contains the spinal cord, an organ of 

 great importance and delicacy, which 

 is thus protected from all ordinary 

 injuries. When in position in the back 

 they do not actually touch one an- 

 other, for between each two is an 

 elastic pad of cartilage which serves 

 as a cushion to relieve jars. The 

 vertebra are connected by ligaments, 

 running between every two vertebra 

 and thus tightly binding all the parts 

 of the spinal column into a firm support. 

 Although the backbone is as a result a 

 strong structure, it possesses, never- 

 theless, a certain amount of flexibility. It has the greatest 

 amount of strength consistent with easy bending of the body 

 from side to side, or forwards and backwards. The verte- 



v Lumtwr 



Sacral 



(Coccyx 

 FIG. 121. THE SPINAL 



COLUMN 



Showing the curves and 

 the separate vertebrae 

 (Thompson). 



