YEAST CELL AND ITS LESSONS 175 



many other termini technici with, which we are familiar, 

 these expressions, ferment, diastase, enzyme, or what-not, 

 must be understood historically; just as logic, metaphysic, 

 analytic organon, etc., can only be apprehended and 

 understood historically. In 1831 Leuchs discovered that 

 saliva possessed the property of saccharifying starch, and 

 fourteen years after Miahle isolated the ferment, and called 

 it salivary diastase, a name far preferable to that bestowed 

 upon it by Berzelius, but which remains to this day, I mean 

 ptyalin. Then followed the discovery that the specific 

 functions of the stomach, liver, and pancreas were each 

 controlled by their specific ferments, which we shall recog- 

 nize as pepsin, rennet, and ptyalin. And now, as the result 

 of the brilliant young Gabriel Bertrand's work, we are 

 even bid to associate the taking up of oxygen by the lungs 

 with the necessary presence of an enzyme, which he has 

 called, appropriately enough, oxydase. 



It is now possible to discern the connection of Buchner's 

 bold experiment with all this more purely physiological 

 work. He proved that the phenomena apparent when 

 yeast is added to the brewers' wort are identical in prin- 

 ciple with all these other fermentive actions, and all the 

 research of more recent years tends but to strengthen one's 

 opinion that the most important functions in the economy 

 of life are under the control of enzymes, or, in other words, 

 partake of the nature of fermentation. Quite recently Dr. 

 Harden has had something to say about zymase. His me- 

 moir is illuminating, and, if that were possible, still further 

 opens our eyes to the complexity of the subject. He indi- 

 cates the presence in yeast juice of "something" of an 

 organic nature which is not affected at boiling tempera- 

 tures, and to which it owes its power of converting sugar 

 into alcohol and carbon dioxide. Should this nameless 

 "something" be withdrawn from yeast juice, zymase al- 

 most loses its characteristic ; but, on the other hand, if more 

 be added, so as to swell the normal quantity, the action of 

 zymase may be doubled or quadrupled in ratio to the quan- 



