736 



THE XERVOUS SYSTEM 



The two sulci are placed dorso-laterally (tig. 438) and the posterior nerve-roots 

 emerge from them. They serve to divide each half of the cord into a posterior 

 and an anterp-lateral area or column (fig, 439). 



The anterior nerve-roots emerge from the antero-lateral aspects of the cord, not 

 from grooves or sulci, but in a relatively scattered manner. They divide the antero- 

 lateral (tolunms into anterior and lateral i)ortions (fig. 439). 



The three septa lie in the dorsal part of the cord; they are a median and two 



Fiu. 439. — Sections through Different Regions of the Spinal Cord. 



(After Sfhvvalbe.) 



POSTERIOR ROOTS 



AXTERIOR ROOTS 



I '(IS TEi: I ( > i: FISS I RE 



A. At the level of the sixth cervical 

 nerve-roots. 



ASTER J OR FISSURE 



B. At the mid-dor.sal resiou. 



CESTRAL CAXAL 



C. At the centre of the luiuhiir eu- 

 largement. 



TV At the u)»per part ot the coniis 

 nieduHaris. 



E. At the level of the tifth sacral 

 nerve-roots. 



F. At the level of the coccygeal 

 nerve roots. 



lateral. The postero-median septum extends throughout the whole length of the 

 cord, separating it into lateral halves dorsally (tig. 439). It consists of neuroglial 

 tissue containing branches of the posterior spinal vessels, and it passes from 

 the pia mater to the posterior, or grey, commissure. The postero-lateral septa 

 are only seen in the dorsal and cervical regions. They extend from the pia 

 mater into the posterior column, dividing it into })ostero-median and jiostero- 

 lat<M-al parts. 



