CHAPTER XXXIV. 465 



formalin, or 1 part of 2-5 per cent, bichromate to 2 of 5 per cent, 

 formalin, the specimens remaining for one day in the first mixture 

 and for two in the second. 



Similarly DUBOSQ (Arch, de Zool. exp., vi, 1898-90). 



SMIRNOW (Arch. mikr. Anat., Hi, 1898, p. 201) fixes the cerebellum 

 of a freshly-killed animal in 5 per cent, potassium bichromate 

 4 parts, and formalin 1 part, for one to eight weeks. He then 

 divides the organ in two halves and places them into pure 3-5 per 

 cent, bichromate, where they are left for another two to five weeks. 

 Of the two halves one may be used for Weigert's myelin stain ; the 

 other is divided in pieces 1 to 2 cm. thick, and these put for one to 

 one and a half weeks into a mixture of 5 per cent, potassium 

 bichromate, 5 parts, and 2 per cent, osmic acid, 1 part. Pieces are 

 then transferred, at first into a weak silver bath and then into the 

 usual 1 per cent, silver nitrate solution. The method gives good 

 results also in human brains of adult subjects. 



ODIER (La Rachicocainisation, Geneve, 1903, p. 27) takes 100 c.c. 

 of Miiller's fluid with 2 c.c. of undiluted formalin and 1 c.c. of 1 per 

 cent, osmic acid. The mixture should be kept in the dark and made 

 up at the instant of using it. Odier finds that formalin-bichromate 

 mixtures generally afford a more abundant impregnation with 

 fewer precipitates than the osmio-bichromic ones. 



BROOKOVER (Journ. comp. neural. , xx, 1910, p. 49) finds useful 

 for adult specimens a preliminary fixation in 4 per cent. " formalde- 

 hyde," neutralised with lithium carbonate or ammonia, before 

 carrying out Golgi's rapid process. 



890. Other Modifications. VASSALE and DONAGGIO (Monit. Zool. 

 Ital., vi, 1895, p. 82) harden pieces of at most 1 cm. in thickness for 

 fifteen to twenty days in a mixture of 5 parts of acetic aldehyde and 

 100 of 3 to 4 per cent, potassium bichromate, changing the fluid as soon 

 as it has become dark. The rest as Golgi. 



EAMON Y CAJAL (Rev. Trim. Histol, No. 2, 1888, note) found that the 

 addition of a very little formic acid to the silver bath facilitated reduction. 

 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 solution. 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. 



M. 30 



