CHAPTER IX. 



THE CULTIVATION OF ANAEROBIC BACTERIA. 



THE presence of uncombined oxygen in ordinary cul- 

 tures inhibits the development of anaerobic bacteria. 

 When such are to be cultivated, it therefore becomes 

 necessary to utilize special apparatus or adopt physical 

 or chemic methods for the exclusion of the air. Many 

 methods have been suggested for the purpose, an excel- 

 lent review of which has recently been published by Hun- 

 ziker,* who divides them as follows, according to the 

 principle by which the anaerobiosis is brought about : 



1 . By the formation of a vacuum. 



2. By the displacement of the air by inert gases. 



3. By the absorption of the oxygen. 



4. By the reduction of the oxygen. 



5. By the exclusion of atmospheric air by means of 



various physical principles and mechanical devices. 



6. By the combined application of any two or more of 



the above principles. 



This classification makes such an excellent foundation for 

 the description of the methods that it has been unhesitatingly 

 adopted. 



1. Withdrawal of the Air and the Formation of a 

 Vacuum. This method was first suggested by Pasteur and 

 was later modified by Roux, Gruber, Zupinski, Novy, and 

 others. It is now very rarely employed. The appropriate 

 container, whether a tube, flask, or some special device such 

 as the Novy jar (Fig. 52), receives the culture, and then has 

 the air removed by a vacuum pump, the tube either being 

 sealed in a flame or closed by a stop-cock to prevent the re- 

 entrance of the air. 



2. Displacement of the Air by Inert Gases. This 

 method is decidedly preferable to the preceding, as it 



* "Journal of Applied Microscopy and Laboratory Methods, " March, 

 April, and May, 1902; vol. v, Nos. 3, 4, and 5. 



227 



