16 CHARLES F. W. MC CLURE, 



Methods ot Investigation. 



1. Methods of Investigating Fresh Material. 



The ganglia were rapidly dissected from the animals, and placed 

 in one of the so-called indifferent fluids, in which the cells were in- 

 dividually isolated. 



Although most of the more common indifferent fluids were used, 

 such as normal salt solution, body fluid, Ranvier's fluid, weak solution 

 of chromic acid and ammonium bichromate, the best results were 

 obtained by progressively staining the cells in methylen blue solutions. 



Dogiel's method of staining nerve cells in a ^/j,o — Vie percent 

 solution of methylen blue, fixing the same in ammonium picrate, and 

 mounting in picric-glycerine (see 7) was tried with only fair results. 

 The difficulty with this method seemed to be that the cells stained 

 so rapidly and so deeply in the above mentioned methylen blue 

 solutions, that all details of structure were obliterated; and were not 

 brought out with any definiteness, even after the immersion in the 

 ammonium picrate. After the failure of this method, which gives 

 such brilliant results for the nerve cells of Vertebrates, the following 

 was substituted, which although by no means perfect, gave fairly 

 good results. 



To a small watch-glass partially filled with equal parts of a 

 normal salt solution and fresh body fluid, from 10 to 30 drops of a 

 Vio P^ï* cent solution of methylen blue^) were added and the three 

 thoroughly mixed. 



It is quite impossible to say exactly how much methylen blue 

 should be added in order to produce a mixture possessing the desired 

 staining intensity. This can only be determined by experimentation, 

 as it was found that all ganglion cells did not always stain alike, 

 even when placed in the same mixture for the same time. Dogiel (6) 

 has similarly shown that the sympathetic nerve cells of Mammals do 

 not all stain alike in the same solution (fig. 2, tab. 12). 



The mixture, however, may be said to possess the proper staining 

 intensity, when nerve cells placed in it stain neither too slowly nor 

 too rapidly, but so gradually take up the stain that at the end of 

 15 to 30 minutes the cell body appears to be stained 

 a much deeper blue than the axis-cylinder process, 

 which should still remain lightly stained. 



1) Made up in a normal salt solution. 



