ii6 Journal of Comparative Neurology. 



days. This is, perhaps, an advantage in so far as one can with 

 sureness obtain certain preparations for demonstrations in a tol- 

 erably brief time. But the advantage is not extended to the 

 fineness of the result since in all such preparations the reaction 

 turns out rather coarse. I was not thereby encouraged to ex- 

 tend experiments in this direction, especially as the abbrevia- 

 tion of the time can be attained in other simpler ways and as 

 the pieces in the chamber quickly pass by the period favorable 

 to the success of the reaction without attaining the kind of 

 hardening sought — which is a not insignificant disadvantage. 



" (c) Hardening in Erlicki s fluid (bichromate of potassium, 

 2^ g.; copper sulphate, ^^ g.; distilled water, lOO g.). Re- 

 garding this I confine myself to stating that the copper salt 

 added to the bichromate did not prevent the reaction and that 

 the Erlicki's fluid possessed the same advantages and disadvan- 

 tages as the preceding method (warm chamber). It accelerates 

 the hardening so that in a i&vi days (6 to 8 to lo) the black 

 stain of various elements of the nervous system can be ob- 

 tained by transferring to silver, but the result cannot be com- 

 mended for fineness. Moreover the period advantageous for the 

 reaction is very quickly passed over. 



" As it appeared to me that the limited and not very fine 

 form of the reaction might be due in part to the rapid action of 

 the hardening fluid, I weakened the same by mixing it in grad- 

 ually increasing quatities with Miiller's fluid (Erlicki 20^ to 

 50^^, Miiller 8o^ to 50%). The results obtained by means of 

 this variation were decidedly good. After only 5 to 6 to 8 days 

 immersion in such a fluid I obtained preparations which in re- 

 gard to fineness of result had a certain worth. It thus appears 

 to me that this variation can be recommended for the purpose 

 of quick demonstrations of cell-forms. For the finest details, 

 especially the relation of the functional processes of the gang- 

 lion cells and the nerve fibers, I find that the first procedure is 

 always to be preferred, or also the following : 



"2. Method of the successive actions of a mixture of osmic 

 acid with bichromate and of the silver nitrate. This procedure 

 also is only a modification of the original but deserves a place in 



