Staining 313 



one-sixth to an equal volume), and after the caustic potash 

 had rendered the sputum perfectly fluid, more or less 

 water was added to dilute the mixture. The sputum, 

 having been measured, was poured into a perfectly clean 

 wide-mouthed bottle containing fine sterilized gravel or 

 broken glass. Rinsings of a measured amount of the 

 caustic potash solution were used to free the conical 

 glass from what matter might remain and were added to the 



Fig. 92. Bacillus tuberculosis in sputum, stained with carbolic fuchsin 

 and aqueous methylene-blue. X 1000 (Ohlmacher). 



sputum. The contents of the bottle were agitated in a 

 snaking machine for five minutes, and allowed to stand 

 until the caustic potash solution had had time to act. So 

 soon as the sputum became homogeneous an equal volume 

 of water was added, and the whole was again shaken. The 

 sputum thus treated was of a pale green or yellowish- 

 brown color, and contained only small fragments of elastic 

 tissue. It was allowed to stand from two to four hours, 

 and was then again shaken for five or ten minutes. 



