156 GENERAL MICROBIOLOGY 



the nutritive substances necessary for anaerobic life. Anae- 

 robic organisms can, in fact, as Tarrozzi has shown, be grown 

 in the presence of the oxygen of the atmosphere by simply 

 adding pieces of animal tissue or some reducing agent to 

 the culture medium. 



Several principles are employed as a basis for the different 

 methods of anaerobic cultivations, as follows: 



I. Exclusion of air from the cultivation. 



II. Exhaustion of air from: 



1. The medium by boiling. This should always imme- 

 diately precede the inoculation of the medium for anaerobic 

 cultivations. 



2. The vessel containing the medium by means of an air 

 pump, i.e., cultivation in vacuo. 



III. Absorption of oxygen from the air in contact with the 

 cultivation, i.e., cultivation in an atmosphere of nitrogen, 

 by means of: 



1. Chemical action upon a readily oxidizable substance 

 in a sealed vessel containing the cultures, e.g., sodium 

 hydroxide upon pyrogallic acid. 



2. Burning a filter paper saturated with alcohol in a 

 sealed vessel. (Moore.) If the paper is well saturated no 

 deleterious products of combustion are formed which would 

 inhibit growth. 



3. Adding to the medium some easily oxidizable sub- 

 stance as dextrose (2%), sodium formate (0.5%), sodium 

 sulphindigotate (0.1%) or fragments of sterile tissue to 

 absorb all the available oxygen held in solution by the 

 medium. 



The chemicals are generally employed in the case of deep 

 stab cultures, the fragments of sterile tissue in broth cul- 

 tures (Tarrozzi's method). The tissue must be freshly 

 removed from an animal (rabbit, mouse, guinea pig, etc.) 

 and only pieces of liver, spleen, kidney or lymphatic glands 

 may be used with success; blood, milk, or the connective 

 tissues are useless for the purpose. Vegetable tissue (potato, 



