372 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



spinal cord, therefore, does not extend the whole 

 length of the vertebral canal but only to the level of 

 the second lumbar vertebra. Its length is about 

 eighteen inches, its diameter one-half inch or less. 

 Membranes of the Cord or Meninges. i. The 

 Dura. This is a thick strong membrane composed of 



Blood capillaries in white matter. 



Spinal 

 ganglion 



Posterior root of spinal nerve 



Ligamentum 

 denticulatum. 



A nterior root of ' 

 spinal nerve. 



Posterior root. 

 Anterior root. 

 Dorsal spinal 



ganglion. 

 Dura mater. 



Arachnoid. 



Pia mater. 



Blood-vessels. 

 Fig. 264. Portion of spinal cord and membranes dissected 



white fibrous tissue which forms the outer covering 

 of the cord. Many blood-vessels find lodgment in 

 this membrane. It is analogous and continuous 

 with the dura of the brain, the most striking differ- 

 ence being that the dura of the cord does not form 



