DO UBLE- IMPREONA TION 507 



then puts small pieces for three to five days into 4 per cent, 

 bichromate, and lastly transfers these into the silver bath, where 

 they are left with advantage for ten to twenty days. 



Bolton {Lancet, 1898 (1), p. 218 ; Journ. R. Micr. Soc, 1898, 

 p. 244) has obtained good results from brains of cats and half- 

 grown kittens placed whole in 5 per cent, formalin and from 

 human brains hardened whole in formalin of the same strength 

 for two to twelve months. Small pieces are then cut out, and 

 placed into 1 per cent, ammonium bichromate and left therein 

 for from a few hours up to five days, some being transferred at 

 intervals into 1 per cent, silver nitrate. 



ScHREiBER (Anat. Anz., xiv, 1898, p. 275) obtained good 

 results from appendages of Crustacea impervious to the osmic 

 mixture, with 5 parts of 2-5 per cent, potassium bichromate to 

 1 of 4 per cent, 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., lii, 1898, p. 201) fixes the cere- 

 bellum of a freshly-killed animal in 5 per cent, potassiund bichro- 

 mate 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- 

 biehromic ones. 



Brookover {Journ. comp. neurol., xx, 1910, p. 49) finds useful 

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

 dehyde," neutralised with lithium carbonate or ammonia, before 

 carrying out Golgi's rapid process. 



1037. 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. 



