NEURO-GLIA -ITS CELLULAR ELEMENTS. 315 



be exactly compared with those of ordinary serous sacs. 

 In the tela chorioides or the plexuses, a series of pheno- 

 mena may certainly manifest themselves, which are pa- 

 rallel to the diseases of other serous parts, but this can 

 never take place in the same manner on the ventricular 

 surface of the brain. 



This peculiarity of the membrane, namely, that it be- 

 comes continuous with the interstitial matter, the real 

 cement, which binds the nervous elements together, and 

 that in all its properties it constitutes a tissue different 

 from the other forms of connective tissue, has induced 

 me to give it a new name, that of neuro-glia* (nerve- 

 cement). The view that the substance in question be- 

 longs to the class of coimective tissues has recently been 

 admitted on nearly all sides, but with regard to the ex- 

 tent to which any isolated structures that occur in it are 

 to be considered as belonging to this substance, opinions 

 are still divided. Even when I instituted my first spe- 

 cial investigations into the structure of the ependyma of 

 the brain and spinal cord, it turned out that certain stel- 

 late ceUs which are met with in the middle of the spinal 

 marrow (in the wall of the central canal, the existence of 

 which was afterwards more accurately demonstrated, 

 namely, in what I called the central thread of ependyma), 

 and which up to that time had been regarded as nerve- 

 cells, unquestionably belonged to the neuro-glia. After- 

 wards, and especially by the Dorpat school with Bidder 

 at its head, a series of investigations were published, in 

 which a great number of cells in the spinal marrow were 

 set down as belonging to this connective tissue. Bidder 

 himself was ultimately led to regard all the cells which 

 are found in the posterior half of the spinal marrow, and 

 therefore those sympathetic and sensitive cells also which 

 you have just seen, as connective-tissue-corpuscles. On 



* y/Ua, glue. TV. 



