ORDINARY STAINING-SOLUTIONS. 159 



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 

 aniline-water solution of either fuchsin, gentian-violet, 

 or methylene-blue ; and ZiehPs 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 added drop by drop 

 until the solution has an opaque appearance, the vessel 

 containing the solution being thoroughly shaken after 

 the addition of each drop. It is then filtered through 

 moistened filter-paper until the filtrate is perfectly 

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

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

 holic solution of either fuchsin, methylene-blue, or gen- 

 tian-violet, preferably fuchsin or gentian-violet. 



Ziehl's carbol-fuchsin solution : 



Distilled water 100 c.c. 



Carbolic acid (crystallized) 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. 



The Koch-Ehrlich solution decomposes after a time, 



