Spinal Nerves. 



145 



Gangl. 



inter- 



vertebr. 



489, The Cervical Portion of the Spinal Cord 



with its Membranes. View from behind. 

 The spinal cord extends only to the first or second lumbar vertebra. 

 The length of the roots of the lumbar, sacral and coccygeal nerves 

 therefore, increases rapidly from nerve to nerve, and may be estimated 

 by the distance of the foramen of exit from the extremity of the cord ; 

 owing to their length and the appearance they present in connection 

 with the spinal cord, the aggregation of the roots of these nerves 

 has been named h o r s e's tail, Cauda equina. At the Conus terminalis of 

 the spinal cord the pia mater is continued as Filum terminals, down to 

 the lower end of the impervious sheath of the dura mater, which runs 

 down to the end of the sacral canal. The intervertebral ganglia of the 

 cervical, dorsal and lumbar nerves lie within the intervertebral foramina ; 

 those of the sacral nerves in the spinal canal external to the dura mater ; 

 those of the coccygeal nerve within the latter. The largest nervous divisions 

 of the spinal cord are the sacral nerves, which form the sacral ple- 

 xus, Plexus sa.cra.Us. 



