28 



ing certain parts of many bacteria, such as the flagella on 

 motile forms, the spores in spore bearing organisms, and 

 the capsule on certain other species. There is a large num- 

 ber of these special methods but in this course only one of 

 each will be given. These will be taken up in connection 

 with the study of the bacteria requiring them. 



§ 32. Formulae for staining solutions. The dyes used 

 are methylene-blue, gentian- violet, methyl-violet, and 

 fuchsin. 



i,oeffi,e;k.'s ai<kaline methyi<ene-bi,de. 



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



Caustic potEish I per cent, solution i c.c. 



Distilled water 100 c.c. 



CARBOI< FUCHSIN (ZIEHI^'S SOLUTION). 



Fuchsin (dry) i gram. 



Alcohol (Absolute) 10 c.c. 



Carbolic acid, 5 per cent, solution 100 c.c. 



Dissolve the fuchsin in the alcohol, after which add the 

 carbolic acid solution. In.stead of using the dry fuchsin 

 and alcohol, 10 c.c. of a saturated alcoholic solution of 

 fuchsin may be used. 



§ 33. Aqueous Solutions. Aqueous solutions of methyl- 

 violet, gentian-violet, fuchsin, and the other aniline dyes 

 are prepared by adding i c.c. of the saturated alcoholic 

 solution of the desired dye to 20 c.c. of distilled water. 

 This will impart a decided color to the liquid so that a 

 pipette full will be barely transparent. 



The true aqueous solutions are made by dissolving the dyes 

 in water, but these are weak and not so effective as those 

 prepared from the alcoholic solutions. These solutions 

 deteriorate in a short time. The carbol fuchsin and alkaline 

 methylene-blue will keep a little longer, but they require to 

 be filtered occasionally. 



