Anaerobic and Aerobic Decomposition 345 



important, for, by destroying tiie resistant cell-walls, 

 they make accessible to other bacteria the nitrogenous 

 and non-nitrogenous substances enclosed within the 

 cell. 



The anaerobic changes in the manure pile do not 

 involve large losses of nitrogen, and the intense activity 

 of the cellulose ferments cannot be regarded, therefore, 

 as prejudicial to the economical transformation of the 

 nitrogen compounds. For this reason, the manure, 

 when kept moist and well compacted, goes through 

 the initial stages of decomposition with large losses of 

 organic matter, but with comparatively small losses of 

 nitrogen. 



Aerobic. — The decomposition of cellulose may also 

 occur under aerobic conditions. Thus the destruction of 

 fallen trees and twigs in the forest is accompanied by 

 the initial softening of the wood, and its gradual crumb- 

 ling to a fine powder. In this case, the work is done 

 not by bacteria but by fungi. Later on, the work of the 

 fungi is supplemented by that of bacteria until the 

 woody tissue is completely destroyed. Besides the 

 fungi, there are also a number of different species of 

 aerobic bacteria that can attack and dissolve cellulose. 

 Certain denitrifying bacteria are credited with this 

 ability, and it is safe to assume that other cellulose- 

 destroying aerobic organisms will be discovered in time. 

 These organisms will be found, most likely, in dry, open 

 soils, in which the humus disappears rapidly, or in the 

 soil used in earth closets and in which the destruction 

 of the organic matter is so rapid as to resemble purely- 

 chemical rather than physiological processes, 



