AXAEROBIC METABOLISM 223 



4. ANAEROBIC GAS METABOLISM 



Carbon dioxide is the gas most commonly evolved when 

 animals are kept under anaerobic conditions. As a mat- 

 ter of fact it was found in almost all the cases in which 

 it was searched for. (Emerson, 1929, using a manomet- 

 ric method in experiments with Amoeba proteus, could 

 not find any trace of carbon dioxide; but it is not clear 

 from his brief account whether the organisms had so 

 little resistance that they died when deprived of oxygen, 

 or whether the method employed was not sensitive enough 

 to register the production of small amounts of carbon 

 dioxide. ) 



A. Liberation of carbon dioxide from inorganic sub- 

 stances. This process will always take place when the 

 medium or the body of the experimental animal contains 

 bicarbonates or carbonates and when, during the course 

 of the anaerobic metabolism, acids are produced that are 

 stronger than carbonic acid, such as, for example, lac- 

 tic or lower fatty acids. As is well known — and this has 

 been mentioned in numerous instances on previous oc- 

 casions — the liberation of carbon dioxide from bicarbon- 

 ates can be used as a convenient index of the extent of 

 the anaerobic metabolism. 



Carbon dioxide measurements can easily be made with 

 manometric methods. One procedure consists in using 

 two manometric vessels with the same amount of medium 

 and the same number of animals, one for the anaerobiosis 

 experiment, the other as control. To the contents of the 

 control vessel is then added, at the beginning, through a 

 side arm, a strong acid that liberates all the carbon diox- 

 ide bound up in the medium and in the bodies of the ani- 

 mals; the contents of the experimental vessel are acidi- 

 fied only at the end of the run. The increase in pressure 

 found in the latter corresponds to the bicarbonates that 

 were still present as such. The difference between this 

 pressure increase and that computed from the data gain- 



