542 SURGICAL APPLIED ANATOMY. [Chap. xxiv. 



outline assumed by the spine, and in some weakly 

 children, and especially in those afflicted with rickets, 

 this curvature is often very pronounced. The discs 

 are twenty-three in number, and make up nearly one- 

 fourth of the entire length of the spine. If the discs 

 be removed, and the vertebrae be articulated in the 

 dry state, the cervical and lumbar convexities almost 

 disappear, and the column tends to present one great 

 curvature, the concavity of which is forwards, and the 

 most marked part of which corresponds to a point just 

 below the middle of the dorsal region. This somewhat 

 resembles the curve seen in the spines of the aged, and 

 in such individuals it may be to no small extent due 

 to the shi'inking of the inter vertebral discs. 



It is by means of the discs that the movements of 

 the spine are in the main permitted, and it will be 

 found that they are most developed in regions where 

 most movement is allowed. They act also as springs 

 in giving elasticity to the column, and in economising 

 muscular action, while at the same time they play the 

 part of buffers in modifying the effect of shocks trans- 

 mitted along the spine. 



Although the motion permitted between any two 

 individual vertebrae is not extensive, yet the degree of 

 movement capable, of being exercised in the column 

 as a whole is considerable. This movement is least 

 free at the dorsal region, and is most extensive in the 

 neck and loins. In the lumbar region (the base of 

 the column) exists the greatest degree of motion per- 

 mitted in the spine, and here is allowed, not only 

 forward and backward flexion, but also lateral bending, 

 and a certain amount of rotation. In the cervical 

 region flexion in the antero-posterior direction is not 

 so ready as it is in the loins, although the neck enjoys 

 the greatest degree of rotation and of lateral flexion. 



Sprains of the vertebral column. The many 

 joints and ligaments of the part, and the varied and 



