132 BACTERIOLOGY. 



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 car- 

 bolic acid. These solutions are as follows : 

 Loffler's alkaline methylene-blue solution : 



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

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



Koch-Ehrlich aniline-water solutions. To about 100 

 c.c. of distilled water aniline oil is added, drop by drop, 

 and the solution thoroughly shaken after each addition, 

 until it is of an opaque appearance. It is then filtered 

 through moistened filter-paper until the filtrate is per- 

 fectly clear. To 100 c.c. of the clear filtrate add 10 c.c. 

 of absolute alcohol and 11 c.c. of the concentrated al- 

 coholic solution of either fuchsin, methylene-blue, or 

 gentian-violet, preferably fuchsin or gentian- violet. 



Ziehl's carbolic-fuchsln solution : 



Distilled water 100 c.c. 



Carbolic acid (crystalline) 5 grammes. 



Alcohol 10 c.c. 



Fuchsin in substance 1 gramme. 



Or it may be prepared by adding to a 5 per cent, 

 watery solution of carbolic acid the saturated alcoholic 

 solution of fuchsin until a metallic lustre appears on the 

 surface of the fluid. 



Both the Koch-Ehrlich and the Ziehl solutions 

 decompose after having been made for a time; par- 

 ticularly is this the case with the former, so that it is 

 better to prepare them when needed in small quantities 

 than to employ old solutions. Solutions older than 

 fourteen days should not be used. 



The three solutions just given may be used for cover- 

 glass preparations in the ordinary way. 



