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has at its disposal for carrying out its chemical reactions with 

 such wonderful efficiency. 



The fermenting action of certain bacteria and yeasts upon sugars 

 and other substances has long been known and used in the 

 industries. These yeasts were called organized ferments, while 

 chemical preparations like pepsin, etc., which exhibit a fermenting 

 or digesting action, were called unorganized ierments. This dis- 

 tinction was retained until 1897 when Buchner performed his clas- 

 sical experiment on yeast, showing that by the action of pressure 

 applied in a hydraulic press he was able to obtain a liquid 

 possessing all the fermenting power of living yeast plants even 

 in the absence of the living organisms. This substance or 

 property of the expressed liquid Buchner called an "enzyme." 

 He said that substances of like nature were products of the life- 

 activities of cells, but were not dependent on the living cell for 

 the exhibition of their characteristic fermenting action. It is to 

 ferments or enzymes like this that the cell owes its great chemical 

 efficiency. Enzymes are members of the class of substances 

 known as "catalyzers" which, by processes that are not fully 

 understood, cause reactions to take place with a speed not shown 

 under ordinary conditions. Generally, catalysts are capable of 

 causing or assisting in reactions without being themselves de- 

 stroyed by the processes they propagate. 



In discussing the oxidases or oxidizing enzymes a somewhat 

 critical attitude is necessary in the face of many conflicting and 

 even contradictory results. To take an example, several of the 

 so-called oxidizing enzymes have been shown to be not enzymes 

 but heat-withstanding inorganic or organic catalyzers. At the 

 present time our knowledge of these substances is being increased 

 almost daily, with the result that we are now in a sort of tran- 

 sitional period, the literature of the whole subject being filled 

 with assertions and denials on the part of equally able investi- 

 gators. The tendency at present seems to be to consider as 

 enzymes those apparently complex organic substances of non- 

 diffusable nature and of high catalytic power, which are produced 

 during the life processes of plants and animals; but when in- 

 vestigation reveals definitely their exact chemical nature, such 



