THE BACK. 91 



Some of the dorsal vertebrae are peculiar in the arrange- 

 ment of their facets and derm-facets, while among the 

 cervical vertebrae are several whose peculiarities should be 

 more carefully noted. Thus, the first cervical vertebra 

 or a^as supports the head and has practically no body, 

 the place of the body being taken by a narrow anterior 

 arch of bone and an opening, continuous with the spinal 

 foramen, into which the odontoid process of the axis fits, 

 being held in place by ligaments. At either side on top 

 is a facet for articulation with the occipital bone. There 

 is almost no spine. The second vertebra or axis has 

 surmounting the body the odontoid process, with a facet 

 in front for articulation with the atlas and one behind 

 for the transverse ligament to move over. The seventh 

 cervical vertebra or vertebra prominens has a very long 

 spinous process hence name to which is attached the 

 liyamentum nuchce. It can be felt very distinctly on 

 the living. 



Running from the skull down through the spinal 

 column into the sacral vertebrae and formed by the join- 

 ing of the spinal foramina of the individual vertebras is an 

 opening called the spinal canal, which holds the cord. 

 The cord, however, stops practically at the first lum- 

 bar vertebra, where it splits up into the cauda equina, 

 only the filum terminate extending farther down. 



Occasionally the laminae do not form completely and 

 the membranes of the cord may bulge out and form a 

 tumor, or the cord itself may come out also. This 

 generally occurs in the lumbar region, where it is known 

 as spina bifida. If in case of fracture of a vertebra there 

 is paralysis of the parts below due simply to the pressure 

 of a fragment of bone upon the cord, it may be completely 

 cured by remoyal of the fragment. If, however, the 

 cord suffers injury, the paralysis will remain. Humpback 

 or Pott's disease is caused by the tubercle bacillus, which 

 eats away the bodies of the vertebra? so that the column 

 caves in and the spinous processes are thrown out in a 

 hump or kyphos. 



