THE CENTRAL NERVOUS SYSTEM. 21$ 



Thus, we find in front of the anterior gray commis- 

 sure, at the bottom of the anterior fissure, a band 

 of horizontally arranged fibres running from one 

 side to the other, called the white commissure. The 

 fibres which pass out of the gray matter to form 

 the roots of the spinal nerves, take also longitudi- 

 nal and oblique courses. 



The nerve elements of the central nervous system 

 are supported and held in place in part by connect- 

 ive-tissue septa and prolongations which-pass inward 

 from the pia mater ; in part by a delicate net-work 

 of a peculiar form of connective tissue called neu- 

 roglia. The latter consists for the most part of fine 

 fibrils, and of irregular-shaped flat-bodied cells, which 

 frequently send off numerous exceedingly delicate 

 branching processes. These cells are called neuroglia 

 cells, and from their numerous and delicate processes 

 are very commonly known as " spider cells." 



In the gray matter of the cord, we have also 

 nerve- and connective-tissue elements and blood- 

 and lymph-vessels ; the first consisting of ganglion- 

 cells and nerve-fibres. The nerve-fibres are in part 

 medullated, in part naked axis cylinders ; and be- 

 sides these, a multitude of extremely delicate gray 

 nerve-fibrils occur, which seem partly to come from 

 the breaking up of axis cylinders, and partly to be the 

 delicate branching processes of ganglion-cells. The 

 nerve-cells of the gray matter are, for the most 

 part, multipolar, and vary greatly in size, the largest 



