CHAPTER XLVII. 

 THE SPINE. 



ANATOMY. LANDMARKS. 



LEVELS OF CENTRES IN FRACTURES AND DIS- 

 SPINAL CORD. LOCATIONS. 



OPERATIONS. 



The spine is composed of thirty-three superimposed 

 bones arranged as follows, viz. : Seven cervical, twelve 

 dorsal, five lumbar, five ankylosed to form the sacral, and 

 four, to form the coccyx. Each vertebra consists of a 

 body, two pedicles and two laminae, which, meeting be- 

 hind, complete the neural arch and form, posteriorly, the 

 spinous process, while, transverse and articular pro- 

 cesses complete the structure of the vertebra. The spi- 

 nous processes occupy the middle line, posteriorly, whereas, 

 on either side, are the transverse processes. Between 

 these two prominences there is a hollow in "the skeleton, 

 which, however, in the body, is filled with the dorsal mus- 

 cles. The tips of the spinous processes correspond to the 

 lower portions of the bodies of the vertebrae in the follow- 

 ing manner, viz. : Each of the cervical, of the three upper 

 and three lower dorsal and of all the lumbar spinous pro- 

 cesses is about on the same level as the lower border of 

 the vertebra to which the spinous process belongs ; where- 

 as, the dorsal spines, from the third to the ninth, corre- 

 spond to the lower part of the vertebra, next below the 

 one to which the spine belongs. Within the spinal canal 

 is the spinal cord with its membranes, viz., the dura mater, 

 the arachnoid and the pia mater; while, leaving its sub- 

 stance, are the roots of the spinal nerves proceeding to the 

 intervertebral foramina. 



