AXIS-CYLINDER AND DENDB1TE STAINS. 423 



alcohol. They are then cleared, first in creasote, in which 

 they should remain only a few minutes, then in oil of turpen- 

 tine, in which they should remain for ten to fifteen minutes 

 (they may remain there for days without hurt). They are 

 then mounted in da-mar (rather than in balsam), and without 

 a cover. Preparations mounted under covers in the usual 

 way always go bad sooner or later, whilst those that are 

 mounted without a cover keep very well, especially if tliry 

 be kept in the dark. GOLGI states that he has a large number 

 that have kept without change for nine years. 



As a general rule thick sections (50 to 60 /i or more) 

 show much more than thin ones, but do not seem to keep so 

 well. 



The order in which the elements of tissues impregnate is 

 generally first, axis-cylinders, then ganglion cells, and lastly 

 neuroglia cells. 



811. GOLGI'S Bichromate and Nitrate of Silver Method, 

 RAPID process (op. cit., p. 33). Small pieces of very fresh 

 tissue are thrown into 



Bichromate solution of 2 to 2*5 per cent. 



strength . . . . .8 parts. 



Osmic acid of 1 per cent, strength . 2 



(Or, later, two parts of bichromate of 3 per cent, to 1 of 

 the osmic acid.) The tissues begin to be in a fit state for 

 taking the silver impregnation from the second or third 

 day ; in the next following days they are in a still more 

 favourable state, but the favourable moment does not last 

 long ; the faculty of impregnation soon declines, and is 

 generally quite lost by the tenth or twelfth day. 



The silver impregnation is conducted exactly as in the 

 slow process, and sections are prepared and mounted in the 

 same manner. (I find that they should not be left in alcohol 

 for more than an hour or so before mounting.) 



There is this difference, that the impregnated material 

 cannot be preserved for any length of time in alcohol, but 

 must not remain for more than tii'o days in it. But it may 

 be kept in the silver solution until wanted for sectioning. 

 According to VAN GEHUCHTEN (La Cellule, vi, 1890, p. 405), 

 material may be kept for six months in the silver, with 

 advantage, showing abundant reductions where none were 



