No. 6. DEPARTMENT OF AGRICULTURE. 333 



takes place in silage. The carbohydrates are mainly attacked with a 

 certain loss of substance, the evolution of carbon dioxide and prob- 

 ably the produclion of organic acids. This process, however, does 

 not continue long but is succeeded by the ordinary bacterial fermenta- 

 tion already stated. 



5. The Decomposition of Proteid Matter. 



Proteid matter is a valuable source of plant food because of its 

 contained nitrogen. This nitrogen before it can be easily assimilated 

 by the plant must be converted into the condition of nitrate. The 

 stages leading up to the production of nitrates are: 



1st. Putrefaction or the conversion of proteid matter into am- 

 monia (ammonification). 



2d. The oxydation of ammonia to nitrites, the first stage of nitrifi- 

 cation, and, 



3d. The oxidation of nitrites to nitrates, the final stage of nitrifi- 

 cation. 



These processes will be considered in turn. 



(a) Putrefaction and Ammonification. 



Liebig^^ and the older investigators considered putrefaction a 

 chemical process, the final products of which were carbon dioxide, 

 w'ater and ammonia. 



In 1837 V. Schwann made the important discovery that fermenta- 

 tion and putrefaction germs were invariably found in the atmos- 

 phere, and it was left to Pasteur and his co-laborers to demonstrate 

 finally that putrefaction was due to the agency of micro-organisms. 



Since the early discoveries of Pasteur it has been shown that a 

 great variety- af bacteria found in soil, water and organically pol- 

 luted fluids are capable of effecting the decomposition of albuminous 

 or proteid matter. 



The first step in the change is the conversion of insoluble pro- 

 teids into soluble peptones, a process similar to that which takes 

 I»lace in the stomach. The liquefaction, or as it is called, the pep- 

 tonization of proteids is effected through the ability of the bacteria 

 to secrete an enzyme of the nature of animal trypsin. All bacteria 

 which liquefy gelatin have peptonizing properties to a greater or 

 less degree, and hence the power of converting proteids into pep- 

 tones. Liquefying bacteria are abundantly present in all soils, hence 

 the vital agcnciesi are there at work which cause a rapid peptoniza- 

 tion of all proteid bodies. 



The next step in the process is the conversion of peptones into 

 amido-acids and basic amines. 

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