74 A MANUAL OF BACTERIOLOGY 



warm solution of aniline-methyl-violet, 1 and then 

 decolourised with nitric acid (one in two). The 

 tissues may be stained brown by immersing them in 

 an aqueous solution of Bismarck brown or vesuvin. 

 In this case the microbes are blue and the tissues 

 brown. Other aniline colours may be used, but the 

 decolouriser is nitric acid. The stained sections are 

 washed, cleared in oil of cloves, and then mounted 

 in Canada balsam. 



In the Baumgarten method cover-glass prepara- 

 tions of sputum are placed in a very dilute solution 

 of potassium hydroxide (potash), and after being 

 slightly pressed on the microscopic slides they are 

 ready for examination. By this method the bacilli 

 (tubercle) are seen in the unstained condition. This 

 is a quick method of examining phthisical sputum, 

 as it does not take more than ten minutes. 



Gibbes' rapid double-staining method is applicable 

 for staining sections as well as cover-glass prepara- 

 tions. No decolourising agent is used, while the 

 double-staining process is performed in one opera- 

 tion. The preparations are allowed to remain in a 

 warm aniline-magenta-methyl- violet solution for five 

 minutes, or in the case of sections for several hours. 

 They are washed in methylated spirit until no more 

 colour comes away. The preparations are now 

 dehydrated in absolute alcohol, dried and mounted 

 in Canada balsam dissolved in xylol. By this 



1 The above solution is prepared by mixing together 100 cc. 

 of a saturated aqueous solution of aniline and 11 cc. of a satu- 

 rated alcoholic solution of methyl violet. The filtered mixture 

 is the Ehrlich-Weigert stain. 



