ORDINARY STAINING-SOLVTIONS 



165 



these simple . solutions it is necessary to employ agents 

 that will increase the penetrating action of the dyes. Ex- 

 perience has taught us that this can be accomplished by the 

 addition to the solutions of small quantities of alkaline 

 substances, or by dissolving the staining-materials in strong 

 watery solutions of either aniline or carbolic acid, instead 

 of water — in other words, by employing special solvents 

 and mordants with the stains. 



Fig. 33 



Rack of bottles for staining-solutibns. 



Of the solutions thus prepared which may always be 

 employed upon bacteria that show a tendency to stain 

 imperfectly, there are three in common use — ^LofHer's 

 alkaline methylene-blue solution; the Koch-Ehrlich ani- 

 line-water solution of either fuchsin, gentian-violet, or 

 methylene-blue; and Ziehl's solution of fuchsin in carbolic 

 acid. These solutions are as follows: 



Ldffier's alkaline methylene-blue solution: 



Concentrated alcoholic solution of methylene-blue 

 Caustic potash in 1 : 10,000 solution . 



30 c.c. 

 100 c.c. 



Koch-Ehrlich aniline water solution. To about 100 c.c. 

 of distilled water aniline oil is slowly added, a few drops 



