STAINING OF TUBERCLE BACILLI 211 



sputum is taken up, and is then rubbed between two cover- 

 glasses. When the sputum is very viscid, the cover-glasses 

 between which the lump is spread out are, before being 

 drawn apart, laid on a hot plate at a temperature below 

 100° C. until a slight clouding takes place, betokening 

 coagulation. The cover-glass preparation, after drying, is 

 passed three times through the flame, and stained in a warm 

 solution of fuchsine or methyl violet in aniline water for a 

 quarter to half an hour. To decolorise, the cover-glass 

 is brought into an acid mixture containing one part nitric 

 acid, two parts water, and two parts sulphanilic acid, or into 



Fiu. 83.— TOBEKCLE Bacilli in' Sputlji. (After Jakscli.) 



a solution of 3 per cent, of hydrochloric acid in 9 per 

 cent, alcohol, after which it is rinsed in 60 per cent. 

 alcohol and double-stained in methyl blue or malachite 

 green if the tubercle bacilli have been stained red, or in 

 vesuvine or Bismarck brown if they have been stained 

 blue. It is then rinsed again, dried, and mounted in 

 Canada balsam. 



Kaatzer has modified the process in the following 

 manner : — The sputum — best that first expectorated in the 

 morning — having been received into a completely empty 

 spitting-cup, is spread out upon a black plate or a piece of 

 black glazed paper. A very minute particle is now picked 



p 2 



