160 A REVIEW OF THE GOLGI METHOD. 



of the sublimate, and for microscopical investigation the action is 

 the same as when there is an actual black stain. But this stain is 

 only an appearance due to the opacity of the elements upon which, 

 probably owing to a reducing action, the mercury has precipitated. 

 In reflected light one notices that the elements appear entirely 

 white; indeed, under stronger magnification they show plainly a 

 metallic lustre. 



" 1 will remark that the particular advantages of this method 

 consist first in the fact that the reaction can take place in large 

 pieces, further that its success is absolutely certain without being 

 necessarily bound by strict rules as to the time of sojourn in the 

 hardening fluid, and finally in the fact that the preparations which 

 it yields requires no especial precautions for their preparation, but 

 can be treated in the usual way, like sections stained with carmine. 



" The mode of application of the sublimate method is only 

 distinguished from the silver method by some unessential things. 

 It likewise consists of two essential processes : 



" {a) Hardening of the pieces in bichromate. 



" {b) Transference of the same into a solution of bichloride 

 of mercury and sojourn in the latter. 



" {a) The hardening in bichromate is done entirely in the usual 

 way. (See the original method.) I only add that the reaction 

 does not proceed in an essentially different manner if consecutively 

 stronger solutions of i, 2, 3 per cent, are employed, or if the 

 pieces are immediately laid in Miiller's fluid. In general it is 

 expedient for the pieces to be small, but this is not absolutely 

 necessary. Good results are also obtained with large pieces, 

 indeed with whole brains. In the latter case the preserving fluids 

 require a long time to penetrate by osmosis from the periphery into 

 the interior, and the central portions could spoil before they expe- 

 rienced the action of the fluid. It is necessary therefore to make 

 a careful preliminary injection of bichromate solution, so that the 

 reagent is well distributed throughout the organ. 



" A few days' (6 to 8 or less) sojourn in the bichromate solution 

 is sufficient to obtain, by putting the pieces into sublimate solution, 

 an extended fine black stain of a greater or less number of cells 

 (indeed one can obtain an indication of the reaction on the fresh 

 brain which is placed immediately in the sublimate solution). A 



