NEUKOGLIA. 



Kolliker to be a form of retiform tissue ; accordingly he named it the reticulum of 

 the nervous centres, but the term neuroglia which was proposed by Virchow has 

 been more generally adopted. It is not, however, of the nature of connective tissue, 

 for it contains neither the characteristic fibres nor cells of that tissue ; nor is it 

 developed from mesoblast but from the neural epiblast. The neuroglia is, in fact, 

 composed entirely of greatly ramified cells (glia-cells), the branches of which pass 

 everywhere in the interstices of the proper nervous elements, and are somewhat 

 modified in their general arrangement according to the nature of the elements which 

 they chiefly support. Thus in the white matter of the spinal cord the branches of 

 the neuroglia-cells can be seen bending round the medullated nerve-fibres and 

 accommodating themselves exactly between them like packing material between 

 parallel glass tubes (fig. 376). In the cerebral cortex, on the other hand, where 

 the arrangement of the nervous elements is 

 much less regular, the branches of the glia- 

 cells have a dense brush-like arrangement such 

 as is shown in fig. 377. 



It has been shown by Eanvier that the glia- 

 cells are fibrillated, the fibrils passing through 

 the body of the cell from one cell-process to 

 another. These are seen in fig. 378, which 

 represents a glia-cell from the spinal cord 

 isolated after maceration in dilute alcohol. 



In addition to these stellate neuroglia-cells 

 a further support is afforded to the nervous 

 matter of some parts of the central nervous 

 system by the ramified prolongations of the 

 ciliated epithelium-cells which line the central canal (spinal cord, &c.). These 

 prolongations extend originally to the outer surface of the spinal cord, and 

 for a considerable period of its early development they can be traced as fine 



Fig. 376. A NEUROGLIA-CELL FROM THE 

 WHITE SUBSTANCE OP THE SPINAL CORD 

 STAINED BY GOLGl's METHOD (E. A. S. ). 



Fig. 877. A NEUROGLIA-CELL FROM THE CEREBRAL CORTEX OF THE MONKEY, STAINED BY GOLOl's 



METHOD (E. A. S.). 



Fig. 378. A NECROGLIA-CELL, ISOLATED IN 33 p. o. ALCOHOL (Ranvier). 



radiating fibres to its periphery. Although these fibres become subsequently obscured 

 by the great development of nerve-cells and fibres between them, it is probable 

 that their remnants persist even in the fully developed condition of the nerve-centre. 

 Lastly, a certain amount of support is furnished to the soft matter of the central 

 nervous system by the prolongations of pia mater (connective tissue sheath of the 



