178 BACTERIOLOGY 



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 solutions. 



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 Loffler'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: 



Lqffler's alkaline methylene-blue solution: 



Concentrated alcoholic solution of methylene-blue 30 c.c. 



Caustic potash in 1 : 10,000 solution 100 c.c. 



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

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



