430 NERVOUS SYSTEM SPECIAL METHODS. 



up to 100 c.c. They are kept therein for from an hour up to six, 

 washed once more in distilled water, passed for twelve to twenty-four 

 hours into the usual 20 per cent, solution of formalin. Wash, 

 dehydrate quickly, embed, preferably in paraffin, tone sections as 

 described above, counterstain, if necessary, mount in balsam. 



B. Method for Pieces with Pyridine Treatment. Pieces of formol 

 material, up to 1 cm. thick for adult tissue, and up to 5 cm. long for 

 embryos, is put for two, three or four days into pure pyridine, 

 washed for some hours in several changes of distilled water and put 

 for three to five days into 3 per cent, silver nitrate at 36 C. Wash 

 in distilled water and transfer into the diluted ammoniacal silver 

 bath as above, but leaving pieces therein for twenty-four hours. 

 Wash for about two hours in several changes of distilled water, 

 reduce in 20 per cent, formalin. The rest as above. 



841. Modifications of BIELSCHOWSKY'S Methods. FAVORSKY 

 (Journ. Psychol. Neural., 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 Stot. Neapel, xviii, 1907, p. 576) fixes fish 

 embryos in 4 per cent, formaldehyde neutralised 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 -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 trans- 

 ferred for twelve hours into a reducing fluid consisting of 1 per cent, 

 hydroquinone 20 c.c., neutralised formalin, 2 c.c. After embedding 

 in paraffin, the sections are toned as usual and counterstained with 

 1 per cent, eosin in absolute alcohol. 



SCHUTZ (N enrol. 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 (Anat. Am., xxxv, 1910, p. 193) has obtained excellent 

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



