332 ANNUAIi REPORT OF THE Off. Doc. 



But the question may be asked', what causes the oxygea of the air 

 to combine with the elements of organic matter whereby this com- 

 bustion is affected. Under ordinary conditions oxygen has no af- 

 finity for organic carbon. Something must be present to stimulate 

 this combination. 



We have already found how water is made to combine with certain 

 organic compounds through the agency of special enzymes, so in ac- 

 cordance with this it has recently been shown that a number of oxy- 

 dation processes can be effected through the agency of another class 

 of enzymes known as oxydases. 



It has been already noted that yeast when in mass developes a 

 rise of temperature, and it has generally been assumed that this is 

 due to the respiratory activities of the cells, but it has recently been 

 shown that there can be extracted from the yeast cells, independent 

 of the cells themselves, a substance which has the power of oxidizing 

 glycogen with a perceptible increase of temperature. 



Thus it appears not to be the vital protoplasm of the cell but some 

 substance w^hich can be extracted therefrom which possesses the 

 power of oxidizing organic matter with the production of heat. This 

 active substance is an oxidizing enzyme. 



It is now quite generally believed that oxidizing enzymes are 

 quite generally distributed throughout vegetable tissues, and that 

 they occur dissolved within the fluids of the cells. 



In the presence of oxygen they cause a union of the latter with 

 carbon, carbon dioxide being evolved. Thus it may be considered 

 at least a working hypothesis that all processes of respiration are as- 

 sociated with the activities of oxidizing enzymes. 



When green fodder is cut and placed in the silo, cells previously 

 protected from the air are exposed, and the combined action of the air 

 and the liberated oxidizing enzymes results in a rapid oxidation with 

 loss of substance. 



When fruits are cut open their exposed surfaces turn dark, due to 

 the combined action of contained oxidizing enzymes and the atmos- 

 phere. 



Besides the ordinary gaseous products of oxidation, it has been 

 shown that oxidizing enzymes may produce certain by-products, 

 notably the organic acids. Thus ensilage may become sour without 

 a trace of bacterial fermentation. 



Fresh olives when placed in heaps ferment. With this there is 

 an increase of temperature, a liberation of carbon dioxide, and the 

 formation of acetic and other fatty acids. Talomei shows this fer- 

 mentation to be due to a special oxidizing enzyme which he called 



When green crops are plowed under their tissues continue to 

 undergo an oxidation or respiratory process similar to that which 



