Chap, vii Enzymes and their Action 401 



than had been imagined to exist. The progress of thought 

 and of research during the later decades of the century 

 tended more and more in this direction, till at its con- 

 clusion the processes of digestion had come to be recog- 

 nized as altogether fermentative in their character, and the 

 term fermentation had been accorded a much wider meaning 

 than it held in the minds of Pasteur and the workers of 

 his time. The old distinction between organized and un- 

 organized ferments was proved unnecessary and misleading 

 by the numerous researches which showed that all these 

 changes are due to the influence of the living cell, working 

 in most cases by the unorganized ferments or, as they 

 came to be designated, enzymes. 



Up to the year i860 but little knowledge of the vegetable 

 enzymes had been obtained. Only a few of them had been 

 discovered, and their distribution in the vegetable kingdom, 

 their mode of action and its conditions were almost entirely 

 unknown. 



We have already spoken of the discovery of one of these 

 enzymes, diastase, in connexion with the original transloca- 

 tion of the starch stored temporarily in the chloroplasts of 

 the leaf, and have briefly described the function it dis- 

 charges. Much more complete information respecting it 

 was derived from investigations made upon germinat- 

 ing seeds, in which a larger amount of material is available 

 for research. Indeed it was from such sources that our 

 first knowledge of it was derived, as our recognition of it 

 as a factor in metabolism only dates back to the researches 

 of Payen and Persoz in 1833 upon the germinating barley 

 grain. 



It is impossible here, from considerations of space, to do 

 more than call attention to the chief workers in this field and 

 to set out very briefly their several results. The renewed 

 interest in the inquiry dated from the work of von Gorup- 

 Besanez in 1874, which resulted in a large addition to our 



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