160 GENERAL MICROBIOLOGY 



pump and (d) while the pump is running, sealing the tube 

 or flask in the flame, at the constriction provided for the 

 purpose. 



2. The special jars have the advantage that tube and 

 plate cultivations may be prepared in the usual way and 

 then placed in the special jar which is then attached to the 

 vacuum pump; when sufficient vacuum has been produced 

 the stopcock is turned between the jar and the pump. 



Isolation of anaerobic organisms may be accomplished 

 with much greater facility by the use of these jars. 



In practically every instance these same jars may also 

 be employed in the methods given under the absorption of 

 oxygen. 



III. ABSORPTION OF OXYGEN 



Different methods illustrating this general principle are 

 much used because of its simplicity and general applicability. 

 Any vessel with a tight cover as a Novy jar, an ordinary 

 chemical desiccator, a Mason fruit jar, etc., may be used 

 as a container for the tube or plate culture. 



A. Pyrogallic add method. 1. Dry pyrogallic acid is 

 placed on top of some absorbent cotton in the bottom of 

 the jar or tube. 



2. A solution of sodium hydroxide is poured in, but not 

 directly upon it. 



3. The cultures are put in place. 



4. The jar or tube is immediately sealed and care is 

 taken to mix the chemicals. The organisms thus grow in 

 the presence of the inert gas nitrogen. 



The chemicals are used in the proportion of 1 gm. of 

 pyrogallic acid to 10 c.c. of 10% aqueous solution of 

 potassium or sodium hydroxide for each 100 c.c. of air 

 space. 



Apparatus. Tubes for use in oxygen absorption method. 



1. Simple test-tube method. 



2. Giltner's H tube. 



