CHAPTER IX 

 THE CULTIVATION OF ANAEROBIC ORGANISMS 



The presence of uncombined oxygen in ordinary cultures inhibits 

 the development of anaerobic bacteria. When such aire to be culti- 

 vated, 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 excellent 

 review of which has recently been published by Hunziker, * 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 rarely em- 

 ployed. The appropriate container, whether a tube, flask, or some 

 special device such as the Novy jar, 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. 



2. Displacement of the Air by Inert Gases. — This method is 

 decidedly preferable to the preceding, as it leaves no vacuum. It 

 is easier to displace the oxygen than to withdraw it, and any appa- 

 ratus permitting a combination of both features, as that designed by 

 Ravenel,t from which the air can be sucked by a pump, to be later 

 replaced by hydrogen, can be viewed with favor. 



The most simple apparatus of the kind was suggested by Frankel 

 who inoculated a culture-tube of melted gelatin or agar-agar, solidi- 

 fied it upon the wall of the tube, as suggested by Esmarch, sub- 



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

 May, igo2; vol. V, Nos. 3,4, ands. 



t "Bacteria of the Soil," "Memoirs of the National Academy of Sciences," 

 First Memoir, 1896. 



21S 



