536 NEUROGLIA AND SENSE ORGANS 



But the Weigert method, whilst staining neurogha fibres and 

 nuclei of neuroglia cells intensely and, up to a point, specifically, 

 leaves the cell-bodies of the latter entirely unstained. It conse- 

 quently led to the erroneous conclusion that the processes of 

 neuroglia cells were one and the same thing as the neuroglia fibres 

 shown by the new method, and that the latter were, in the 

 adult state, only contiguous to — ^viz., independent of — ^the cell 

 body. 



Efforts were, therefore, made to discover new methods suitable 

 for the study of neuroglia fibres and neuroglia cells and their 

 reciprocal relations. Many modifications of Weigert's neuroglia 

 stain, the methods of Benda, Mallory, Anglade and Morel, 

 Held, Rubaschkin, Da Fano, etc., may be considered as the 

 direct outcome of such efforts. 



None of these methods, however, was sufficient to entirely 

 solve the problems resulting from Weigert's discovery and from 

 the comparison between the results attainable by the new neuroglia 

 stain and Golgi's process. 



Of these the most obvious difficulty arose from the fact that 

 many neuroglia cells were stained in the cerebral cortex by 

 Golgi's method which were not revealed by Weigert's stain. 

 Ramon y Cajal in 1913 published his gold-sublimate method 

 which stained all the neuroglia cells electively and revealed the 

 structure of the cortical cells as well as those which Weigert's 

 method showed. It proved that the cortical neuroglia cells 

 differed in structure from the majority of the neuroglia cells 

 found elsewhere in the nervous sytem. The term " protoplasmic 

 neuroglia " was then applied to these cells, who do not contain 

 the fibres demonstrated by Ranvier and Weigert, and the term 

 ''fibrous neuroglia " to those which do. 



Other methods published by Achiicarro and Del Rlo-Hortega 

 confirmed Cajal's work, but revealed, in addition, the processes 

 of two other cell forms, which older writers had called " satellite 

 cells" or "undifferentiated glia cells." There is now general 

 agreement on the distinction of these two cell types, one of which, 

 the " oUgodendroglia " or " interfascicular glia," is probably a 

 true neuroglial cell, whereas the other, the " microglia" appears 

 to be mesodermal in origin, and to be closely related to the reticulo- 

 endothelial system of Aschoff . 



It may be said at once that none of these cells except the 

 fibrous neuroglia cells can be stained in their entirety by any 

 anil in stain. For their demonstration the only methods so far 

 successful have been impregnations with metals such as silver, 

 gold or platinum. Ford Robertson appears to have been the first 

 to stain the oligodendroglia by a platinum method {Scottish Med. 

 & Surg. Journ., 1899). Further modifications of these methods 

 have demonstrated rounded bodies or gliosomes on the cell- 



