406 CENTEAL NERVOUS SYSTEM. 



a white or yellowish tint (may be kept 



in stock) . . . . . 15 drops. 



b. Distilled water 3 c.c. 



c. Saturated solution of phosphate of iron 

 in distilled water (the usual pharma- 

 ceutical solution) .... 3 5 drops. 



d. Sulphurous acid . . . .3 c.c. 



Mix a, b, and c, and add d, which will cause a voluminous 

 precipitate, at which instant the mixture is to be poured over 

 the section, or the section brought into it, as in method a, 

 the remaining treatment being exactly as there described. 



The principle of the two methods is the decoloration of 

 the impregnated elements (especially glia-cells) up to a cer- 

 tain point by means of the potash, or potash and f erricyanide, 

 or the vanadate and permanganate. It is important to 

 take care that this decoloration be not overdone, as if car- 

 ried too far the axis-cylinders and ganglion-cells will be 

 decolourised. 



772. WEIGEET'S Saurefuchsin method mentioned above appears to be 

 definitively superseded by his hsematoxylin method. See, however, Centralb. 

 f. d. med. Wiss., 1882, pp. 753, 772; Fortschr. d. Med., 1884,Nos.4and6; 

 Zeit.f. wiss. Mik., 1884, pp. 123, 290. 



773. SAHLI (Zeit.f. wiss. Mik., 1885, p. 1) gives the following method : 

 Sections of tissue hardened in bichromate to the degree required for 

 Weigert's hsematoxylin process are washed for not more than five or ten 

 minutes in water, and stained for several hours, until they are of a dark blue 

 colour, in concentrated aqueous solution of methylen blue. They are then 

 rinsed with water, and stained for five minutes in saturated aqueous solu- 

 tion of Saurefuchsin. If now they be rinsed with alcohol and brought into 

 a liberal quantity of water, the stain becomes differentiated, axis-cylinders 

 being shown coloured red and the myelin sheaths blue. - If, instead of rins- 

 ing with pure alcohol, alcohol containing from O'l to 1 per cent, of caustic 

 potash be taken, the stain differentiated in water, and the sections cleared 

 with cedar oil and mounted in balsam dissolved in cedar oil, still finer 

 images are obtained. Axis-cylinders are red as before, but the myelin 

 sheaths are blue in some places, red in others. Sahli thinks that this 

 reaction points to some difference of kind in the nerve-tubes that exhibit it. 



The same author (1. c., p. 50) also gives a method for obtaining a specific 

 stain of nerve-tubes by means of methylen blue alone. Sections of material 

 hardened as before are stained for a few minutes or hours in the following 

 liquid : 



Water .40 parts. 



Saturated aqueous solution of methylen blue . 24 

 5 per cent, solution of borax . . . . 16 

 (Mix, let stand a day, and filter.) 



