508 PERIPHERAL NERVE-FIBRES 



Ramon y Cajal {Rev. Trim. Histol., No. 2, 1888, note) found that the 

 addition of a very little formic acid to the silver bath facilitated reduc- 

 tion. According to van Gehuchten {La Cellule, vii, 1891, p. 83) 1 drop 

 of the acid should be added to every 100 c.c. of the silver nitrate solu- 

 tion. But the practice is now generally abandoned. 



Martinotti {Rif. med., 1887 ; Ztschr. wiss. Mikr., v, 1888, p. 88) 

 pointed out that Golgi's method can be successfully carried out on 

 relatively large pieces by using unusually large quantities of silver 

 nitrate solution with 5 per cent, glycerin added to it, and by keeping 

 this for thirty days at a temperature of 25° C. to impregnate nerve-cells, 

 and of 35° to 40° C. to stain the neuroglia. 



Andriezen {Brit. Med. Journ., i, 1894, p. 909) found useful for 

 human brain to suspend thin slices of 2 to 4 mm. in diameter in 95 c.c. 

 of 2 per cent, potassivun bichromate to which after ten to fifteen minutes 

 5 c.c. of 1 per cent, osmic acid are added. The mixture is kept in the 

 dark and after twenty-four hours changed for a fresh one made up 

 with 90 c.c. of 2| per cent, bichromate and 10 c.c. of 1 per cent, osmic 

 acid. After another two days the mixture is changed over again for 

 one made according to the proportions given by Golgi (3 per cent, 

 potassium bichromate, 80 c.c. ; 1 per cent, osmic acid, 20 c.c). Pieces 

 are transferred into the silver bath after three and a half days (for nerve- 

 cells and neuroglia) up to six days. They are washed for five to fifteen 

 minutes in f per cent, silver nitrate, and then put into a solution of 

 silver nitrate of the same strength, but to which 1 drop of formic acid 

 to every 100 or 120 c.c. of solution has been added. The whole is kept 

 in an incubator at 25° to 27° C. for about three days, changing the 

 silver bath after the first twenty-four hours. The same author advised, 

 for the impregnation of neuroglia {Intern. Monatschr. Anat., x, 1893, 

 p. 533), adding 1 drop of a saturated solution of chromic acid and 1 drop 

 of formic acid to the first hardening bath. 



Berkeley {Johns Hopkins Hosp. Rep., vi, 1897, p. 1) hardens tissues 

 in Muller's fluid until they are of sufficient consistency to admit of fairly 

 thin sections (about two weeks at room temperature). The portions 

 of the brain selected are cut into slices 3 mm. thick and immersed for 

 about three days in a mixture of 3 per cent, potassium bichromate, 100 

 parts, and 1 per cent, osmic acid 30 parts. For the impregnation, 

 tissues are removed from the hardening fluid, dried a little with filter 

 paper, washed in a weak solution of silver nitrate, and put for no less 

 than two to three days into a freshly-prepared solution of 2 drops of 

 10 per cent, phosphomolybdic acid and 60 c.c. of 1 per cent, silver 

 nitrate, which in winter should be kept at a temperature of about 26° C. 



Hill {op. cit. § 1031) uses, instead of silver nitrate, a | per cent, 

 solution of silver n?7rj7e, with 01 per cent, formic acid added. 



GuDDEN {Neurol. Centrbl, xx, 1901, p. 151) uses the lactate of silver 

 (sold as " actol "), and finds it more penetrating. 



1038. Avoidance of Precipitates. Golgi's method frequently 

 gives rise to the formation at the surface of the pieces of irregular 

 and sometimes voluminous precipitates, which destroy the clear- 

 ness of preparations. To minimise this, Sehrwald {Ztschr. 

 wiss. Mikr., vi, 1889, p. 456) pours 10 per cent, gelatin, which is 

 just liquid, into a paper box, imbeds the tissues in it with the 

 aid of a little heat, and brings them therein into the silver bath ; 

 or the tissues are coated with gelatin by dipping and cooling 

 several times. After the impregnation is completed the gelatin 



