VERTEBRAL COLUMN. 391 



great use in preventing the sudden displacement 

 of the vertebrae ; for this effect cannot be pro- 

 duced by any force short of that which would 

 occasion fracture. Any one who will try to dis- 

 locate, by sheer force, the spine of a hare or 

 rabbit will find reason to admire the art with 

 which its bones have been locked together, and 

 the skill displayed in combining great flexibility 

 with such powerful resistance to every effort 

 that can be made to separate them. 



For the purpose of allowing a passage to the 

 spinal marrow, the bodies of the vertebrae 

 (b. Fig. 177 and 178), are hollowed out behind, 

 into a groove, over which a broad plate of bone is 

 thrown from the sides of the vertebrae, like the 

 arch of a bridge. The succession of arches, 

 when the vertebrae are joined together, forms a 

 continuous canal, which is occupied by the 

 spinal marrow. Notches, corresponding to each 

 other, are left in the sides of each of the arches, 

 forming apertures for the secure passage of the 

 nerves as they issue from the spinal marrow. 

 All these circumstances are visible in the figures, 

 particularly in the section, Fig. 179, where c, c, 

 is the canal for the spinal marrow, and in which 

 the apertures just mentioned are distinctly seen, 

 at o, o. 



In order to give an advantageous purchase to 

 the muscles which are attached to the spine, 

 each vertebra has, besides the parts above des- 



