120 PHYSIOLOGICAL CHEMISTRY. 



finally the problem was solved by the German chemist Buch- 

 ner, who in 1897 succeeded in isolating the active enzyme from 

 yeast cells and in quantity too. This enzyme he called zy- 

 mase; it was found to be as active as the yeast itself and to do 

 all that could be expected of yeast. It has since been pro- 

 duced on the commercial scale in the endeavor to supplant the 

 use of yeast in practice. More recently it has been shown that 

 other ferment cells secrete enzymes and it is possible that all 

 the so-called organized ferments work in this way; but the 

 isolation of the soluble active principle seems to be very diffi- 

 cult in most cases. 



All this, however, affords us no real insight into the nature 

 of the ferment process. We have as yet no satisfactory theory 

 as to how these active chemical principles behave in the break- 

 ing down of other organic substances. It has not been found 

 possible to prepare any enzyme in a condition of even approxi- 

 mate purity and all analyses made of such substances are 

 doubtless wide of the truth. These analyses appear to show 

 that the enzymes are of protein character, but the impurities 

 in the products analyzed may be responsible for this indication. 

 With this lack of knowledge regarding the chemical composi- 

 tion of the ferments it is naturally impossible to offer a chem- 

 ical explanation of how they act. It is the effects only that 

 we are familiar with and all our classifications are practically 

 based on what the ferments can do rather than on what they 

 are. It is known that all ferments are destroyed by heat and 

 by the action of even rather weak acids and alkalies. In this 

 they resemble the cells that produce them. While the true 

 ferments or enzymes are apparently complex chemical sub- 

 stances their formation is due in every case, at least it so ap- 

 pears, to cell action. They are organic, but not organized; 

 yet they possess many of the properties of organized bodies. 

 On the other hand certain finely divided metals, especially col- 

 loidal platinum, bring about a number of reactions which were 

 long supposed to be characteristic of the true ferments ; these 

 reactions are further modified or suspended by the same sub- 



