344 Bacteria in Relation to Country Life 



The greater proportion of carbon dioxid found 

 toward the bottom of the heap may generally be readily 

 accounted for by its comparatively high specific gravity 

 and its tendency to sink down, but, more especially, by 

 the greater amount of cellulose fermentation in the 

 lower part of the heap. Similarly, the increase of 

 marsh gas toward the bottom of the heap may be taken 

 as a certain indication of the more intense cellulose 

 fermentation taking place there. The accompanying 

 decrease in the proportion of nitrogen indicates the 

 more or less complete exclusion of atmospheric air. 



The ferments. — From these facts it may be seen that 

 the cellulose ferments are anaerobic. Confirmation of 

 this is furnished by a series of observations extending 

 throughout the latter half of the last century and crowned 

 by the investigations of Omelianski, begun in the spring 

 of 1894. Omelianski isolated in pure culture two dis- 

 tinct species of rod-shaped anaerobic ferments capable 

 of gradually dissolving strips of Swedish filter paper. 

 The two species, while closely resembling one another 

 in appearance, were found to differ in their physiological 

 activities. In the gaseous products formed by one of 

 them, marsh-gas was present in large proportion, while, 

 in the gaseous products of the other, hydrogen took 

 the place of the marsh gas. 



The two organisms. — the marsh gas (methane) fer- 

 ment and the hydrogen ferment are widely scattered 

 in nature and are met with in all soils, and at the bottom 

 of ponds, lakes, rivers and canals. There they are con- 

 cerned with the destruction of woody tissues under 

 anaerobic conditions. Their work in the manure pile is 



