308 



BACTERIOLOGY. 



Displacement of air. — This can be accomplished by pass- 

 ing through the tube or apparatus a current of inert gas. 

 Hydrogen is employed most often for this purpose. Car- 

 bonic acid has been employed by Pasteur and others, but 

 it is not as indifferent a gas as hydrogen. If employed, it 

 should be washed by passage through a solution of sodium 

 carbonate. Illuminating gas may be used with fair results. 



Fig. 50. Simple bottle for anaerobes (F. G. N.). 



The Liborius tube which is most often mentioned in this 

 connection is a test-tube with a constriction below the neck. 

 At a distance of about 2 inches from the bottom a narrow 

 side-tube is attached, and is continued on the inside almost 

 to the bottom of the test-tube. After the medium is inocu- 

 lated a current of hydrogen is passed into the tube, through 

 the side-tube, until the air has been displaced. When this 

 result is attained the tube is sealed below the cotton plug 

 and finally the side-tube is likewise sealed. Various modi- 

 fications have been proposed, but although they render the 



