STAINING IN GENERAL. 159 



Wash carefully in water and alcohol, and then im- 

 merse for a few seconds in the " sensitizing bath/' viz., 

 a 0.25-0.5 per cent, solution of silver nitrate. With- 

 out washing, bring the slip into a watch-crystalful of 

 the " reducing and reinforcing bath/' viz.: 



Gallic acid 5 grains. 



Tannin 3 " 



Fused pot. acetate 30 " 



Dist. water 350 " 



After a few seconds pass the slip back into a watch- 

 crystal containing the dilute silver bath (0.25-0.5 per 

 cent, solution of silver nitrate in water) and keep it 

 in constant motion until the solution begins to take on 

 a brown or blackish color. Wash in water thoroughly ; 

 dry with blotting-paper, and mount in balsam. 



STAINING IN GENERAL. 



The physics of staining and decolorization is hardly 

 a subject to be discussed at length in a book of this 

 character; but, as Kuhne has pointed out, it may be 

 said that solutions which favor the production of diffu- 

 sion currents facilitate intensity of staining, and by a 

 similar process increase the energy of decolorizing 

 agents. For example, tissues which are transferred 

 from water into watery solutions of the coloring mat- 

 ters are less intensely stained and more easily decolor- 

 ized than when transferred from alcohol into watery 

 staining-fluids; for the same reason tissues stained in 

 watery solutions of the dyes do not become decolorized 

 so readily when placed in water as when placed in 

 alcohol. 



The diffusion of staining-solutions into the protoplasm 

 of dried bacteria, as found upon cover-slip preparations, 



