302 ELEMENTARY PHYSIOLOGY. [XXIX. 



coat sends into the cord numerous septa. 

 Note the blood-yessels running from the pia 

 mater into the cord along the septa. 



b. The anterior and posterior fissures ; the 



pia mater dips down into the anterior fissure; 

 the posterior fissure contains a prolongation 

 of the inner coat only of the pia mater, the 

 outer coat running over the fissure. 



c. The entrance into the cord of the anterior 

 roots of the spinal nerves in several small 

 bundles. 



d. The entrance into the cord of the posterior 

 roots of the spinal nerves in a compact 

 mass. 



e. The white substance 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 (cp. c.) 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. 

 g. The central canal ; it may be plugged up 

 with epithelial cells ; 



h. A ring of deeply stained neuroglia around 

 the central canal, and 



