CHAPTEK II 



MECHANISM OF THE SPINE 



THE brain-case is thus a perfect whole, secure 

 on all sides, and strengthened where the exposure 

 to injury is the greatest. We shall see, in the 

 column which sustains it, equal provision for the 

 security of the brain ; and, what is most admira- 

 ble, there is an entirely different principle intro- 

 duced here ; for whereas in the head, the whole 

 aim is firmness in the joinings of the bones, in 

 the spine which supports the head, the object to 

 be attained is mobility or pliancy. In the head, 

 each bone is firmly secured to another; in the 

 spine, the bones are not permitted to touch : there 

 is interposed a soft and elastic material, which 

 takes off the jar that would result from the con- 

 tact of the bones. We shall consider this subject 

 a little more in detail. 



The spinal column, as it is called, serves three 

 purposes : it is the great bond of union betwixt 

 all the parts of the skeleton ; it forms a tube for 

 the lodgment of the spinal marrow, a part of the 

 nervous system as important to life as the brain 

 itself ; and lastly, it is a column to sustain the 

 head. 



