444 SOILS: PROPERTIES AND MANAGEMENT 



were it not for the other process putrefaction. Putre- 

 faction is produced by anaerobic bacteria. In the same 

 body, and consequently in the same soil, decay and putre- 

 faction may be in progress simultaneously, decay taking 

 place on the outside and on the surfaces of other parts 

 exposed to the air, while putrefaction occurs on the in- 

 terior, where the supply of oxygen is limited. By means 

 of the two processes, decomposition is greatly facilitated. 

 Decay (see Fig. 61) produces a very rapid and complete 

 decomposition of the substance in which it operates, most 

 of the carbon and hydrogen being quickly converted into 

 carbon dioxide and water, and the nitrogen into ammonia 

 and probably some free nitrogen. The latter is possibly 

 due to the oxidation of ammonia, thus 



4 NH 3 + 3 O 2 = 6 H 2 O + 2 N 2 



The sulfur of the proteins finally appears in the form of 

 sulfates. 



What the intermediate products are has not been deter- 

 mined, but in the decay of meat, in which there was an 

 abundant supply of oxygen, succinic, palmytic, oleic, and 

 phenyl-propionic acids have been found. 



Putrefaction results in a large number of complex inter- 

 mediate compounds and proceeds much more slowly. 

 Many of the substances thus produced are highly poison- 

 ous, and most of them have a very offensive odor. They 

 may be further broken down by decay when the condi- 

 tions are suitable, or by a continuation of the process of 

 putrefaction. In either case, the poisonous properties 

 and the odor are removed. 



In the process of decomposition of organic matter two 

 classes of substances are produced : (1) those that have 

 been excreted or secreted by the bacterium, and therefore 



