HISTOLOGY OF THE CENTRAL NERVOUS SYSTEM OF THE WEDDELL SEAL. 143 



The postero-lateral and intermedio-lateral masses of grey matter are united by 

 strands of neuroglial tissue, which break up the lateral regions of the cord into a well- 

 marked reticular formation. The grey matter in general is characterised by its deeply 

 staining neuroglia fibres, which are of a somewhat coarse nature, and are apparently 

 less in number per unit area as compared with the supporting tissue of higher types 

 of cord. 



H 



rfc 



fr.%. 



K 



m. 



CL-K. 



FIG. 1. A transverse section of the spinal cord (upper cervical region). 



a.f. Anterior median fissure. 

 p.f. Posterior median fissure. 

 p.r. Posterior root-bundles. 

 a.r. Anterior root-bundles. 

 f.g. Funiculus gracilis(posteriormediancolumn), 



showing an indication of the beginning 



of the nucleus gracilis. 



p.h. Posterior horn of grey matter (beginning 

 of the substantia gelatinosa of Rolando). 

 i.l.h. Intermedio-lateral horn. 

 f.r. Format io reticularis. 

 a.h. Anterior horn. 

 p. in. Pia mater. 



In the central region of the section the posterior grey commissure is of wide extent, 

 and a small amount of neuroglia is to be seen anterior to the central canal of the cord : 

 the latter is flattened antero-posteriorly, and is lined by a well-marked layer of 

 columnar ciliated epithelium. 



The postero-median fissure is of about the same length as the anterior median 

 fissure, perhaps slightly longer ; but the cord has apparently been subjected to a certain 

 amount of mechanical pressure, causing flattening, and giving the whole section the 

 appearance of abnormal transverse as compared with antero- posterior diameter. The 



(BOY. soc. KDIN. TRANS., VOL. xivra., 851.) 



