164 BACTEEIOLOGICAL AND ENZYME CHEMISTRY 



of mud from the bottom of a stagnant pond in which fermenta- 

 tion has been shown to take place by the production of gas 

 on stirring the deposit on the bottom, are added. The flask 

 is Med up with water and attached to a Hempel gas burette. 

 On keeping the flask for some days at a temperature of about 

 35° C. gas will be evolved, and the filter paper will show signs 

 of pitting, and after the expiration of possibly some weeks 

 will finally be completely disintegrated. On testing the gas it 

 wiU be found to be inflammable, burning with a non-luminous 

 bluish flame, and if analysed can be shown to consist mainly of 

 marsh gas, CH^, together with smaller quantities of hydrogen, 

 H, and carbon dioxide, COj. 



This fermentation has been very carefully worked out by the 

 Russian chemist, Omehanski. For the purpose of his investi- 

 gation he used Neva mud and pure Swedish filter paper ; he 

 was able to isolate two different organisms, one of which pro- 

 duced marsh gas and the other hydrogen. His method of 

 separation depended on the fact that both organisms formed 

 spores, and the spores of the hydrogen organism were able 

 to withstand a higher temperature than those of the marsh- 

 gas organism. On starting the fermentation the marsh-gas 

 fermentation is predominant ; by heating the mixture for 

 fifteen minutes to 75° C. at this stage, the marsh-gas organism 

 was kiUed, but the spores of the hydrogen organism were 

 unaffected. On re-inoculating a fresh quantity of filter paper 

 from the heated solution, the hydrogen organism mainly 

 developed, and by a succession of similar operations he suc- 

 ceeded in obtaining pure cultivations of the two bacteria. 

 They were found to be almost identical in appearance 

 and both produced spores. They differed only in their 

 optimum temperature of reaction and in their resulting 

 products. 



He was able to show that the products obtained completely 

 accounted for the weight of paper originally taken, certain 

 fatty acids being produced together with the gas. Thus in the 



