THE MICROSCOPE AND MICROSCOPIC METHODS 4 1 



Methylene blue works more slowly and feebly; it is to be preferred 

 where the bacteria occur in thick or viscid substances, like pus, 

 mucus, and milk. 



Aniline-water Staining Solutions. — The intensity with which 

 aniline dyes operate may be increased by adding aniline oil to 

 the solution : 



Aniline oil 5 c.c. 



Water 100 c.c. 



;^ix, shake vigorously, filter through wet filter paper. The fluid 

 after filtration should be perfectly clear. Add — 



Alcohol •. . 10 c.c. 



Alcoholic solution of fuchsin (or gentian violet, or 



methylene blue) i c.c. 



Aniline-water staining solutions do not keep well, and need to 

 be freshly prepared about every two weeks. The appHcations 

 of the aniline-water stains will be given under separate headings. 

 In general, however, they are employed where a stain of unusual 

 power is required. 



Sterling's Gentian Violet— Mix 2 c.c. aniline oil with 10 c.c. of 

 95 per cent alcohol and add 88 c.c. of distilled water. Grind 

 5 grams of gentian violet in a mortar, slowly adding the mixed 

 liquid while grinding. Filter. The solution keeps and stains 

 rapidly in Gram's method. 



Carbol-gentian-violet. — Grind i gram gentian-violet in a 

 mortar with 10 c.c. absolute alcohol; then add 2 grams pure 

 crystals of carbolic acid and mix. Add distilled water, 70 c.c, 

 and transfer the whole to a clean bottle. Rinse the mortar with 

 a further 30 c.c. of distilled water and add this to the contents of 

 the bottle. Filter into a clean bottle after 24. hours. This solu- 

 tion keeps well and is used for staining by Gram's method. 



Carbol-fuchsin. — The intensity of staining may also be in- 

 creased by the presence of carbolic acid. The most common 

 example of this is carbol-fuchsin. 



, Saturated alcoholic solution of fuchsin lo c.c. 



S per cent aqueous solution carboHc acid loo c.c. 



