THE CULTIVATION OF MICRO-ORGANISMS 



^33 



one containing a solution of potasgium permanganate and a 

 thiid of silver nitrate. In diluting sulphuric acid, the acid 

 must be poured slowly into the water, and the mixture cooled in 

 a bath of cold, water, or under the tap. Carelessness in dilut- 

 ing this acid may allow violent boiling to occur, sometimes with 

 serious consequences. 





Fig. 59. — An aerobic organism (potato bacillus) that will not grow vtnder a cover- 

 glass. 



For critical work in anaerobic culture it is well to combine 

 the pyrogallate and hydrogen methods. This is readily accom- 

 plished by placing the Petri dishes on a low glass tripod with a 

 small amount (2 grams) of pyrogallic acid beneath them on the 

 bottom of the Novy jar.^ On top of the stack of Petri dishes is 

 placed a small flask containing strong solution of sodium hydrox- 

 ide, and provided with a siphon spout (see Fig. 58). A rubber 

 tube is attached to this spout and leads down to the floor of the 

 jar. After hydrogen has been passed through the jar and it has 

 been finally closed, a slight tipping to one side starts the flow of 

 the alkali through the siphon and so makes the pyrogallic acid 

 available to absorb the last traces of oxygen. 



' MacNeal, Latzer and Kerr, Journ. Infect. Diseases, 1909, Vol. VI, p. 557. 



