HOW TO USE IT. 251 



chloric acid to 5 of water, then wash in water, dehydrate with 

 alcohol. I have found it useful in demonstrating the neuroglia 

 cells and processes to stain in carmine ; and instead of completely 

 clearing up, treat with methylated spirit instead of absolute 

 alcohol, leave long enough to drive out only part of the water ; 

 clear up partly in clove oil, mount in dammar, and examine at 

 once. 



Weigert's Improved Method.*— If sections are to be stained 

 by this method, they should always be hardened by Mullers or 

 Erlitzki's fluids. The latter is made of bichromate of potash, 5 

 parts; sulphate of copper, i part; water, 200 parts; and the 

 time taken is about eight or ten days, and the hardening fluid 

 must not be washed out before placing the piece of tissue in the 

 freezing microtome. The sections should be cut before the 

 pieces have been soaked in water or placed in alcohol for perma- 

 nent preservation. 



Staining. — Make some sections, and always examine them first 

 in a drop of glycerine before staining, if the ordinary stains are 

 desired. If Weigert's method is employed to harden tissue, do 

 not wash and imbed in celloidin. Moisten the blade of the knife 

 with alcohol, and place the sections as cut in that fluid. First, 

 immerse the sections in haematoxylin fluid, prepared as follows : — 

 Hsematoxylin, 075 to i part; alcohol, lo'o parts; water, 90*0 

 parts. Boil the mixture, and allow it to stand for some days to 

 " ripen" before being used. The dye may be rendered ready for 

 immediate use by the addition of i cc. of a cold, saturated solu- 

 tion of carbonate of lithium to 100 cc.'s of the hsematoxylin 

 fluid. Place a watch-glass with the sections and solution in a hot- 

 air bath, at a temperature of between 35*^ and 45 *? C. The time 

 varies. For spinal cord, one or two hours is sufficient, whilst 

 cerebral tissue often requires twenty-four hours. The tissue is 

 now of a blue or black colour ; transfer to the differentiating 

 fluid, which is prepared as follows : — Borax, 2 parts ; ferrocyanide 

 of potassium, 2\ parts; water, 100 parts. Soak for from half-an- 

 hour to an hour, or more. The grey substance is now pale yellow 

 or brown, whilst the white matter remains dark blue or black. 



• " Fortschritte der Medicin," 1884, Bd. II., Nos. 60, 86, Bd. III., No. 8. 



