334 CENTRAL NERVOUS SYSTEM. 



has almost disappeared. The knife should not be wetted 

 with alcohol; the tissues should never be allowed to come 

 into contact with alcohol. Only a small quantity of gold 

 solution, relatively to the volume of the sections, should be 

 taken. The impregnation should last for twelve hours. 



Gierke, 1. c., says : " G-erlach's gold preparations have never 

 had their equal for the demonstration of very fine nerve- 

 fibrils. Weigert's Saurefuchsin preparations are the only 

 ones that can be compared with them in this respect/' 



SCHIEFFERDECKEE (Arch, f. mik. Anat,, 1874, p. 472) also 

 recommends gold chloride for demonstrating fine networks in 

 transverse sections. Strength 1'5000 or 10,000. Time about 

 one to three hours. After washing in water the sections are 

 put for twenty-four hours into acetic acid of J to 1 per cent, 

 then mounted in balsam. 



According to the same author, chloride of palladium may 

 advantageously be used for the demonstration of the longitu- 

 dinal fibres (and, of course, therefore) for staining longitudinal 

 sections. A solution of 1*10,000 strength is taken; the sec- 

 tions remain in it till light brown (about three to five hours) . 



For some further methods of the same author, see 1. c., 1878, p. 38. 



WEIGEET'S Sdurefuchsin method mentioned above appeal's to be defini- 

 tively superseded by his hsematoxylin method. See, however, Centralb.f. d. 

 med. Wiss., 1882, pp. 753, 772 ; Fortschr. d. Med., 1884, Nos. 4 and 6 ; 

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



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 hjema- 

 toxylin 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 con- 

 centrated aqueous solution of methylen blue. They are then rinsed with 

 water and stained for five minutes in saturated aqueous solution of Saure- 

 fuchsin. 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 rinsing 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 dilTer- 

 ence 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 m;iteri;il 

 hardened & before T stained I'm- :\ fVu minutes or hours in Hie following 

 liquid : 



