64 PHYSIOLOGY OF BACTERIA 



1912a) found that a Bad. coli having the gas ratio 

 1.03-1.09 in vacuo showed the gas ratio 5.4 in presence 

 of oxygen. Another strain, with the gas ratio 1.77 in 

 vacuo, changed in air from 3.4 to 590. 



The gas ratio of Clostr. Welchii belonging to the group 

 of anaerobic butyric organisms, was not changed essen- 

 tially by the presence of air (1.42-1.53 in vacuo, 1.44 

 to 1.85 in air) though some oxygen was adsorbed by the 

 culture. Oxygen, apparently, could not be activated to 

 act as acceptor. 



Even in vacuo. Bad. coli will change the gas ratio 

 with the medium. With ammonium lactate as the only 

 source of nitrogen, the gas ratio was 1.03, 1.06 and 1.09 

 in three parallel experiments, while with 1% peptone 

 Witte, it increased to 1.31, and with beef infusion and 

 peptone Witte, it was 1.28. 



{h) THE MECHANISM OF FERMENTATION 



The Mechanism of Fermentation has been claimed to 

 be essentially the activation of certain hydrogen atoms in 

 the substrate molecule. This activation is brought 

 about by a catalyst in the cell. The catalyst is sup- 

 posed by some to combine temporarily with hydrogen 

 and then give it up to some hydrogen acceptor. Such 

 catalysts are used commercially; the best known inor- 

 ganic hydrogen catalyst is metallic nickel, which is 

 used in the industrial hydrogenation of fats. Palladium 

 will dehydrogenate ethyl alcohol or hydrated acet 

 aldehyde and transfer the hydrogen either to oxygen 

 or to methylene blue, thereby changing the dehydro- 

 genated product to acetic acid and acting in the same 

 way as do the vinegar bacteria. 



Possibly, the catalyst or activator only loosens the 

 bond with which the hydrogen atom adheres to the 



