MICROBIOLOGY OF SEWAGE. 215 



plex symbioses as well as bacterial antagonisms that are involved in the 

 reactions with which we are dealing. 



During these reactions proteins and albumins are hydrolyzed by suc- 

 cessive stages to albumoses, peptones, amino-acids, amines, and finally to 

 ammonia, carbon dioxide, methane, hydrogen, etc. Simultaneously am- 

 monia, amines, and carbon dioxide are eliminated at each stage as side 

 products. The tendency then is toward simple, soluble and gaseous 

 products, and hence of value in the preliminary resolution of the 

 sewage. 



The Fermentation of Cellulose. The fermentation of cellulose is, next 

 to protein hydrolysis, the most important work of the anaerobic bacteria in 

 sewage treatment. So far as is definitely known this action is usually 

 confined to anaerobic conditions. The fact that fence posts decay first at 

 the surface of the ground, or that wood in general decays more rapidly 

 when it is exposed to only a slight degree of moisture, than when it is 

 immersed in water is only an apparent contradiction. The conditions 

 are aerobic in both cases and aerobic bacteria would not be favored by 

 total immersion but the effect in both instances seems to be due to fun- 

 gus growths which are more active in the moist wood. 



The anaerobic fermentation of cellulose is that which is found typically 

 in marshes and of which the chief products are carbon dioxide and 

 methane or "marsh gas." Nitrogenous food material is also requisite, 

 which accounts for the preserving property of reasonably pure water 

 upon wood. 



In the septic tank the solution of cellulose is extremely rapid, and 

 large pieces of cotton cloth or rolls of paper are completely dissolved 

 within a few months. Wood itself is more resistant and withstands the 

 action of the tank for years. This is largely due to the fact that the wood 

 molecule is much more complicated than a simple cellulose molecule, 

 and, among the conifers at least, to the further fact that antiseptic 

 intercellular substances are present. 



Chemically considered the action is hydrolytic and can be imitated by 

 prolonged boiling in dilute acids. Pectin substances, starches and finally 

 sugars are produced while butyric and other organic acids, carbon dioxide 

 and methane appear as by-products. Bacteriologically, although it 

 has variously been ascribed to one or another organism, it is probably the 

 result of the activities of many and is possibly not the principal activity of 

 any one of these. In other words, cellulose fermentation is probably a 



