40 A MANUAL OF ANATOMY 



are formed by the apposition of the superior and inferior vertebral 

 notches of contiguous pedicles. They lead outwards from the 

 spinal canal, and each transmits a spinal nerve. They increase 

 in size from above downwards until the sacrum is reached, in which, 

 though hidden at either side of the central mass, they diminish 

 in size from above downwards. In this region each intervertebral 

 foramen opens on the front and back of the sacrum by means of an 

 anterior and posterior sacral foramen, the arrangement thu? formed 

 resem' ling a capital V, the apex being at an intervertebral foramen. 

 On the lateral aspect of the thoracic portion of the column are 

 seen the costo-capitular facets, which are twelve in number. The 

 first is situated on the upper part of the side of the first thoracic 

 body. The second to the tenth inclusive are situated on the 

 contiguous margins of the bodies of the vertebrae, each being 

 formed by the small inferior demi-facet of the upper body and the 

 large superior demi-facet of the lower. The eleventh and twelfth 

 are situated on the sides of the corresponding pedicles. The tenth 

 facet may belong entirely to the tenth thoracic vertebra. The 

 thoracic transverse processes, except the eleventh and twelfth (and 

 sometimes the tenth), are faceted in front at their extremities 

 for the tubercles of the ribs. 



When the column is viewed from behind the following parts 

 are seen : the spinous processes ; the laminae ; the articular pro- 

 cesses ; the backs of the transverse processes ; and the dorsum of 

 the sacrum and coccyx. The cervical spines, except the sixth 

 and seventh, are short, so as not to interfere with backward 

 flexion or over-extension of the neck. The middle thoracic spines 

 are imbricated, and the lumbar spines stand out horizontally. 

 On either side of the spines there is the vertebral groove, which is 

 occupied by the deep muscles of the back, the deepest being the 

 multifidus spinae. This groove is bounded internally by the spines, 

 and externally by the transverse processes in the cervical and 

 thoracic regions, and by the mammillary tubercles in the lumbar 

 region. The floor is formed by the laminae, and its continuation 

 over the back of the sacrum is known as the sacral groove. 



The spinal canal is situated behind the bodies of the vertebrae, and 

 is formed by the neural foramina of all the vertebrae except the 

 fifth sacral and four coccygeal. It commences at the level of the 

 atlas, and it terminates as a rule upon the back of the body of the 

 fifth sacral vertebra. It adapts itself to the various curves of the 

 column, and is large and triangular in the cervical and lumbar 

 regions, small and circular in the thoracic, and triangular in the 

 upper part, but crescentic in the lower part, of the sacral region. 

 It contains the spinal cord and its membranes as low as about the 

 level of the disc between the first and second lumbar bodies, and a 

 copious plexus of vessels. Below the level just mentioned it con- 

 tains the filum terminale of the spinal cord and the leash of nerves 

 known as the cauda equina, with their coverings. The dura- 

 matral covering or theca ceases by taking attachment to the back 



