234 PRACTICAL HISTOLOGY [XXXI 



The white substance, consisting chiefly of medul- 

 lated nerve fibres, forming the outer part of the cord 

 and divided on each side by the entrance of the nerve 

 roots into anterior, lateral and posterior columns ; 

 since the fibres of the anterior root do not enter the 

 cord in one bundle there is no definite line of division 

 between the anterior and lateral columns. 



The grey matter projecting on each side into an 

 anterior and a posterior cornu, but with no distinct 

 separating line between them. The posterior cornu 

 is divided into the neck, the head, and the apex, the 

 latter pointing to the surface along the line of entrance 

 of the nerve roots. 



The large multipolar cells of the anterior cornu. 



The central canal; it may be plugged up with 

 epithelial cells. 



A ring of deeply stained neuroglia around the 

 central canal. 



On either side of the central canal the posterior 

 or grey commissure deeply stained. 



The anterior or white commissure consisting of 

 fairly large decussating nerve fibres in front of the 

 anterior grey commissure ; some may perhaps be traced 

 from the anterior cornu of one side to the anterior 

 column of the opposite side. 



A deeply stained area, the substantia gelatinosa, 

 just internal to the apex of the posterior cornu. It 

 will be better seen in the specimen 6. 



The reticular area in the lateral part of the posterior cornu, 

 a little in front of the substantia gelatinosa, consisting of bundles 

 of fibres surrounded by a small amount of grey substance. 



