202 STUDY OF INDIVIDUAL BACTERIA-STAINING 



are solutions of the anilin dyes. These dyes, as is well 

 known, are of nearly every conceivable color and shade but 

 relatively very few are used in bacteriological work. The 

 beginning student will rarely use solutions of other than 

 the three dyes fuchsin (red), methylene blue and gentian 

 violet for staining bacteria, with occasionally Bismarck 

 brown, or eosin, or safranin as tissue contrast stains. 



The bacteriological dj-es are kept "in stock" as saturated 

 solutions in 95 per cent alcohol, which are never used as 

 stains but merely for convenience in making the various 

 staining solutions. 



The approximate percentages of the three common dyes 

 in such solutions are indicated in the following table adapted 

 from Wood's Chemical and Microscopical Diagnosis, third 

 edition, 1917, Appendix: 



Fuchsin 3.0 per cent. 



Gentian violet 4.8 " 



Methylene blue 2.0 



The stains made from these dyes which are in most com- 

 mon use are the following : 



1. Aqueous (watery) gentian violet solution. 



Saturated alcoholic solution of gentian violet ... 1 part 



Distilled water 20 parts 



Mix well and filter. 



2. Anilin gentian violet: 



Saturated alcoholic solution of gentian \aolet ... 1 part 



Anilin water (see below) 10 parts 



Mix well and filter. 



3. Anilin fuchsin: 



Saturated alcoholic solution of fuchsin 1 part 



Anilin water (see below) 10 parts 



Mix and filter. 



These stains rarely keep longer than ten days in the 

 laboratory (unless kept in the ice-box) and must be made 

 fresh on the first sign of a deposit on the glass of the con- 

 tainer. 



