The Fermentation Tube 



203 



and in every case this ratio of CO, to H was the same. The 

 somewhat crude method of measuring the gas, the contrac- 

 tion of its volume when removed from the thermostat, the 

 fluctuating temperature of the room, the presence of a layer 



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of foam on the surface of the liquid in the closed branch after 

 the COj has been absorbed, all these factors enter as slightly 

 disturbing elements and make the values quoted as only ap- 

 proximately correct. As might be anticipated from the 



