FERMENTS. 463 



with the ferments as such. We only recognize their presence by their 

 activity, which alone distinguishes them. This, in principle, is the same 

 for the organized as the unorganized ferments. The cell produces fer- 

 ments, which it requires for its own economy, and others, which it 

 sends out, to produce results that will directly or indirectly benefit 

 it. The assumption that the ferments which were active when away 

 from the cells had other powers than those remaining in the cell was 

 entirely arbitrary. Especially, as it had never been found possible to 

 isolate such a ferment, i.e., an organized one, from the cell, and bring 

 it into activity in its isolated form, there was no logical ground for 

 sharply differentiating between organized and unorganized ferments. We 

 know that all ferments are more or less subject to external influences. 

 Definite conditions must be fulfilled to develop their action. Thus, for 

 most ferments the optimum temperature lies between 35 and 45 C. The 

 reaction of the medium in which the development occurs is also of con- 

 siderable importance. Pepsin, for instance, requires a hydrochloric acid 

 solution, while trypsin acts in a neutral or faintly alkaline medium. When 

 we find, furthermore, that the formation of ferments by the cells and their 

 activation has recently been recognized as a complicated process dependent 

 upon certain influences, we can readily understand why a definite ferment 

 ceases to act when it has been torn away from its original sphere of activity. 

 We do not know how many ferments the individual cell contains. It is very 

 probable that the ferments are first produced in an inactive form, as zymo- 

 gens, and only activated by the cells when they are needed. It is also 

 possible that the individual ferments are very closely related in their work, 

 i.e., they act together, and assist one another. We also know that many 

 ferments have their action restricted by the decomposition products which 

 they themselves produce. Such an accumulation of cleavage-products 

 would hardly occur in the cell itself, for they are quickly acted upon by 

 other ferments. If, however, such a cell-ferment were forced to develop 

 its activity outside of the cell, we can easily see how it might soon cease 

 to be efficient. 



The discovery by E. Buchner, 1 that it is possible to isolate and separate 

 from the cell structure, the ferment from yeast which converts sugar into 

 carbon dioxide and alcohol, proved for the first time that the similar effects 

 of ferment and cell activities are evidently due to the fact that the same 

 agents are at work in each case. This discovery, which does away with 

 our previous distinction of ferment and enzyme, was carried out in the 

 following manner: Buchner 2 ground a kilogram of yeast with a kilogram of 

 quartz-sand and 2.3 kilograms of infusorial earth. His purpose was to 



1 E. Buchner, H. Buchner and M. Hahn: Die Zymasegarung. Miinchen & Berlin 

 (1903). 



2 Albert and Buchner: Ber. 33, 266, 971 (1900) 



