CHAPTER XXXII. * 



NERVOUS SYSTEM SPECIAL METHODS, CHIEFLY CYTOLOGICAL. 



824. Introduction. The ordinary methods of cytology are, of 

 course, available for nerve cells ; but there are certain constituents 

 of these cells, as well as of nerve fibres, which require, for minute 

 study, special methods, such as the following :- 



A. Methods for Cells, demonstrating Tigroid Substance and 



other Granular Materials. 



825. Tigroid substance or bodies, chromophilic or chromatophilic 

 substance or material or granules, Nissl's bodies or granules, etc., are 

 all denominations for a markedly basophil substance which appears 

 as blocks, granules or irregular patches within the cytoplasm of 

 nerve cells under certain conditions of fixing and staining. 



It is now almost universally admitted that this substance exists 

 in the living cells as a fluid or semi-fluid ' plasm rich in nutritive 

 value," and that the blocks, granules or patches are appearances 

 chiefly due to the coagulation of this plasm, as brought about by 

 the fixing agents employed for their demonstration. As, however, 

 these bodies or granules appear always the same under constant 

 optical conditions in healthy cells fixed and stained in a constant 

 manner, they are said to be the equivalent of such healthy cells during 

 life. " It follows that if the cells, prepared by the same method 

 and examined under the same conditions, show a difference from 

 the equivalent or symbol of healthy cells, the difference is the 

 measure of some change that has occurred during life." See 

 HALLIBURTON, Handbook of Physiology, London, 1920, p. 194. 



This is pointed out here to make it quite clear why NISSL has 

 always insisted that his method should be carried out according 

 to his suggestions, and in a constant manner. At first (N enrol. 

 Centrbl., iv, 1885, p. 500) he used to stain sections of material 

 fixed in alcohol with a warmed watery solution of magenta red or 

 dahlia violet or vesuvine, and to differentiate them with alcohol. 

 Later (Allg. Ztschr. Psych., xlviii, 1892, p. 197) he suggested floating 

 sections on a warmed solution of methylene blue (B patent), with 



* Re-written by Dr. C. Da Fano, King's College, University of London. 



