248 MICROBIOLOGY 



stain this organism are Ehrlich's solution of aniline-water 

 gentian-violet and Ziehl's * carbol fuchsin solution. 8 Much 8 

 found a bacterium resembling that of tuberculosis morpho- 

 logically but which did not retain the stain when treated with 

 the decolorizing solutions. He refers to it as a non acid-fast 

 tubercle bacterium. In staining Bact. tuberculosis, therefore, 

 the preparation must be first deeply stained and then treated 

 with a solution of a mineral acid such as nitric or sulphuric 

 and thoroughly washed. The tubercle bacteria, if present, will 

 .remain deeply stained while the other bacteria and tissues 

 will be decolorized. The preparations may be counterstained, 

 in which case the other bacteria and tissues will be colored. 

 Oabbett 10 combined decolorization and counterstaining in 

 one solution. This consisted of methylene blue 1 gram; cone, 

 sulphuric acid 25 grams; and distilled water 100 cc. After 

 staining in the carbol-fuchsin solution the preparations are 

 covered with this decolorizer for a few seconds and washed in 

 water. The tissues and other bacteria will be stained blue. It 

 has been found that a large number of saprophytic acid-fast 

 bacteria will become decolorized if treated with a 3% solution 

 of hydrochloric acid in 95% alcohol. There are, however, a 

 few non-pathogenic acid-fast bacteria that can not be differ- 

 entiated from the tubercle bacteria by this method. 11 The 

 bacterium retains the stain when treated with the Gram 

 method. 



Cultivation. Bacterium tuberculosis is an aerobic or- 

 ganism, wilich is cultivated without difficulty on blood serum, 

 egg medium, glycerin bouillon and potato, after it has been 



* Kinyoun recommends the following formula: 



Basic fuchsin 4 grams 



Carbolic acid c. ,p. 8 grams 



Alcohol 95% 20 cc. 



Distilled water 100 cc. 



Stain 3 minutes without heat. 



* Ziehl. loc. cit. 



* Much. Beitr. z. Klinik der Tub., Bd. IX, p. 415. 

 "Gabbett. loc. cit. 



Peterson. Kept, of N. Y. State Vet. Coll., 1909-10, p. 65. 



