Irving Hardesty 233 



which do stain blue. That the neuroglia fibers so stain is the chief 

 means by which they are distinguished as such. In other words, the 

 usual descriptions of neuroglia only apply to such fibers as are capable 

 of being thus differentiated by the special stains, though it is perhaps 

 true that only the fully developed fil)ers or those of a certain chemical 

 nature give the blue reaction. Other forms of the non-nervous tissue 

 of the spinal cord are stained brownish-red, or different shades of pink, 

 by the sodium sulf-alizarate employed in the method. 



In the earlier stages of the pig, before the neuroglia fibers are devel- 

 oped, the nuclei alone are stained by the blue. The general spongio- 

 blastic tissue stains deep enough pink for its structure and arrange- 

 ment to be studied with ease, but the alizarin is not to be trusted to 

 bring out cell l^oundaries when present. Therefore, in the earlier stages, 

 other methods were used also. For the adult neuroglia, however, the 

 Benda method exceeds all others for clearness of detail of the neuroglia 

 fibers and for sharpness of contrast. 



The Formation, Early Growth and Primitive Form op the 



Syncytium. 



It is unquestioned that in the earliest stages of the embryo, the cen- 

 tral nervous system is at first composed of individual cells, distinctly 

 outlined and definitely arranged. At this stage His, 87, states that the 

 cells are neither connected with themselves nor with the periphery. 

 That at about the time of the closing of the neural tube, the membranes 

 of these cells begin to disappear and their cytoplasm becomes fused 

 into a more or less common mass, has been shown by several investi- 

 gators of this stage of the growth of the nervous system. His's papers 

 of 83, 86, 87 and 89 often refer to the fusion, and in the illustrations 

 certain of the conditions resulting from it are shown. Schaper, 97, and 

 others of those investigating the mitosis and distribution of the cells 

 of the early nervous system also show these conditions. 



The general name of ncurospongmrn or myelospongkim has been 

 applied to this early form in the central system, but, after studying its 

 formation and the changes it undergoes in the later development, it 

 seems to me that the term syncytiurn, as used in other cases, is more 

 expressive of the nature and behavior of the substance resulting from 

 the fusion of the cells. I have found in the literature no description 

 distinctly considering it as a syncytium and no account of the modifi- 

 cations it undergoes in the development of the adult form of the sup- 

 porting tissue of the central nervous system. 



