THE IDENTITY OF NEUROGLIA. 545 



roglia, though present in greater abundance, as a rule, than 

 in the white substance, varies considerably, the net-work of 

 fibers being especially thick in certain parts. "The neuroglia 

 is present in greatest abundance in the gray matter immedi- 

 ately surrounding the central canal of the cord and the ven- 

 tricles of the brain (the ependyma, as it is called)," says 

 Stewart 41 : a suggestive feature in connection with the views 

 submitted in the present chapter. The neuroglia-cells, as is 

 well known, are of two kinds: those provided with mossy proc- 

 esses and those that have smooth extensions. A large number 

 of investigators still consider that the latter represent true 

 processes, and that, by freely anastomosing, they make up the 

 mesh-work which surrounds the nerve-cells and their prolonga- 

 tions. Eanvier, however, after a searching study of the sub- 

 ject, was led to conclude that the smooth processes of these 

 (stellate) glia-cells, were in reality neuroglia-fibers which 

 merely passed through the latter in all directions, without 

 forming part of the cellular structure per se. We have seen 

 that Apathy's neuro-fibrils, when they left the "nerve-cell," 

 also passed through the cells after forming a reticulum in the 

 latter: a feature which suggests that Apathy's neuro-fibril and 

 the neuroglia-fiber may be structurally similar. 



It was formerly thought that neuroglia was a variety of 

 connective tissue, but this view no longer prevails. Indeed, 

 so distinct is the latter from neuroglia that the two structures 

 can be differentiated from each other by the simplest tests; 

 thus, Eanvier and Malassez found that connective tissue placed 

 in cold water was not modified after several days' maceration, 

 whereas neuroglia-fibers were completely destroyed after two 

 or three days. On the other hand, connective tissue was com- 

 pletely destroyed by prolonged boiling in water, while neu- 

 roglia was hardly altered under similar conditions. The sug- 

 gestive relationship between Apathy's neuro-fibrils and glia- 

 fibers offers some ground for the belief that glia-fibers are also 

 nervous elements. This appears to be sustained by the fact 

 that identical results ensue when nerve-fibers and connective 

 tissue are submitted to the last of the two tests mentioned, the 



Stewart: Physiology, p. 671, 1900. 



