STAINING BACTERIA. 191 



Baumgarten' s Method. In this method the spu- 

 tum dried upon a cover-glass is moistened with a 

 very dilute solution of potash, one or two drops 

 of a thirty-three per cent solution in a small 

 watch-glass filled with distilled water. According 

 to Baumgarten the bacilli may now be seen with 

 a power of 400 to 500 diameters. The film of 

 sputum is then allowed to dry, and the cover- 

 glass is passed two or three times through the flame 

 of an alcohol lamp, after which it is treated with 

 an aqueous solution of one of the aniline colors. 

 Baumgarten asserts that by this treatment the 

 decomposition bacteria are deeply colored, while 

 the tubercle-bacilli remain absolutely colorless. 



EhrlicJis Method. This method is considered 

 by Koch a decided improvement upon his own, 

 and has been employed with success by numerous 

 observers in various parts of the world, especially 

 for the examination of sputum. This is spread 

 upon a cover-glass in as thin a layer as possible ; 

 and, in order to fix the albumen, the cover-glass 

 is passed through the flame of a lamp three or 

 four times, or kept at a temperature of 100 to 

 110 C. for an hour. The staining solution is pre- 

 pared as follows : About five parts of pure aniline 

 (" aniline oil ") are added to one hundred parts of 

 distilled water, well shaken, and filtered through 

 a moistened filter. A saturated alcoholic solution 

 of fuchsin, methyl-violet, or gentian-violet, is 

 added to this mixture, drop by drop, until pre- 



