490 BIELSCH0W8KY 



If necessary the operations described in (3) to (5) can be 

 repeated once more after a thorough wash of the sections. 



1022. Modifications of Bielschowsky's Methods. Favorsky 

 (Journ. Psychol. Neurol., vi, 1906, p. 260) uses 10 per cent, silver 

 nitrate for the first silver bath instead of 2 or 3 per cent. 



Paton (Mitth. Zool. Stat. Neapel, xviii, 1907, p. 576) fixes fish embryos 

 in 4 per cent, formaldehyde neutrahsed with carbonate of magnesia. 

 For the first silver bath he uses 0-75 to 1 per cent, silver nitrate and 

 keeps material therein four days in summer, five to seven in cooler 

 weather. To make the ammoniacal silver nitrate-and-oxide bath he 

 takes 20 c.c. of 0-75 to 1 per cent, silver nitrate, adds to it 4 drops of 

 40 per cent, caustic soda and then ammonia drop by drop in the usual 

 way. The embryos are first washed in distilled water, then kept for 

 five to fifteen minutes in 10 c.c. of water acidified with 5 drops of 

 acetic acid, washed once more in pure water, and transferred for twelve 

 hours into a reducing fluid consisting of 1 per cent, hydroquinone 20 c.c, 

 neutralised formalin 2 c.c. After imbedding in paraffin, the sections are 

 toned as usual and counterstained with 1 per cent, eosin in absolute 

 alcohol. 



ScHiJTZ (Neurol. Centrbl., xxvii., 1908, p. 909) finds that the times 

 given by Bielschowsky are too short and washes sections for twenty- 

 four hours after the 2 per cent, silver nitrate bath, leaves them thirty 

 to forty minutes in the ammoniacal silver bath, and twenty-four hours 

 in the 20 per cent, formalin. For toning he puts them for ten minutes 

 into 10 c.c. of water with 2 drops of acetic acid, then for thirty to forty- 

 five minutes into 10 c.c. of water with 3 drops of a 1 per cent, gold 

 chloride solution (until blackish -grey). 



BoEKE {Anal. Anz., xxxv, 1910, p. 193) has obtained excellent results 

 by the use of Bielschowsky's method for pieces when applied to the 

 study of peripheral nerve-endings. He fixes in 10 per cent, formalin 

 prepared with 60 per cent, alcohol, changes the fluid two or three times, 

 and then either leaves material therein until wanted or keeps it in 70 

 to 80 per cent, alcohol. For staining, pieces are brought into 10 to 12 

 per cent, formalin, and left in it until they are quite free from alcohol. 

 After washing, place in 2 per cent, silver nitrate for three to five days 

 in the dark. Wash in distilled water rapidly, and place in Bielschowsky's 

 silver oxide solution for one to two hours in the dark. Wash rapidly 

 and reduce in 20 per cent, formalin. Imbed blocks in paraffin and cut 

 sections. 



Boeke finds that the method succeeds also after other kinds of 

 fixation. 



ScHLEMMER (Ztschr. zviss. Mikr., xxvii, 1910, p. 22) makes the 

 ammoniacal silver nitrate-and-oxide bath by adding to any silver 

 nitrate solution, 40 per cent, caustic soda, drop by drop, until no more 

 precipitate is formed. He then washes the precipitate by repeated 

 decantation imtil the wash -water no longer gives an alkaline reaction, 

 takes it up with the smallest possible quantity of ammonia, and filters 

 through glass-wool. This concentrated solution keeps for many days 

 unaltered, and should be diluted ten times its volume before using it. 



Deikun {Ztschr. zviss. Mikr., xliii, 1926, p. 380) gives the following 

 directions for making up Bielschowsky's silver solution. All glassware 

 must be thoroughly cleaned, and finally washed with distilled water. 

 The solution must be freshly prepared at the moment of use ; 2 c.c. of 

 a 10 per cent, solution of AgNOg are poured into a test-tube, and 1 drop 

 of 40 per cent. NaOH added to it. Shake gently and wait for the 

 precipitate to fall to the bottom of the tube ; add another drop of 40 



