No. 6. DEPARTMENT OF AGRICULTURE. 331 



(d) The Action of Oxidizing Enzymes in the Fermentation of Veg- 

 etable Matter. 



It is a common phenomenon that where grass or green hay is made 

 into a pile the interior will begin to ferment, and with this there 

 will be a considerable rise of temperature. A similar process goes 

 on in the manure heap, and another when green fodder is packed in 

 the silo. 



In the silo the temperature in the center of the fermenting mass 

 may rise as high as 150 degrees F. With this fermentation there is a 

 considerable loss of organic matter which may vary from 4 to 40 per 

 cent. The temperature as well as the loss of material in the silo 

 is dependent upon the amount of air, or more properly the oxygen 

 present, and this depends upon the looseness or density of the pack- 

 ing. The change is manifestly one of combustion due to the ab- 

 sorption of oxygen, and the products of this change are the same 

 as those evolved in any other combustive process, i. e., carbon 

 dioxide and water. Furthermore, the amount of carbon dioxide 

 evolved is a measure of the degree of combustion and of the organic 

 matter consumed, as well as of the heat produced. 



Formerly it was supposed that the fermentation of silage was due 

 to the agency of bacteria, but now it is believed to be simply an ex- 

 pression of the vital energies of the plant cells. All vital energy 

 manifests itself in the production of heat; this heat is the result of 

 oxidation, or the actual burning or destruction of a portion of the 

 vital substance. Yeast when massed into a heap shows a rise of 

 temperature due to its vital energies. This rise takes place only 

 in the pres^ence of oxygen or air, and in a vacuum no such increase 

 of temperature occurs. The germination of seed is accompanied 

 by a rise of temperature, and oxygen is necessary to the process. 



The animal body gives off heat and the air we breathe is the 

 draught for this ever consuming fire within, while the carbon dioxide 

 exhaled is a measure of the rapidity of this combustion process. 



In a similar manner plants evolve heat and their substance is, in a 

 measure, oxidized or burned to supply this heat, a portion of which is 

 converted into the vital energies of the plant. 



Respiration is the breathing-in of air and the breathing-out of 

 the gaseous products of combustion. This takes place in both 

 animals and plants, nnd heat is the result. Hence when green vege- 

 table matter composed of living cells is massed together these pro- 

 cesses of respiration will continue for a time, and heat is the re- 

 sult. When such matter is massed together the heat evolved can 

 not readily escape, and a considerable elevation of temperature is the 

 result. 



