464 LECTURE XX. 



destroy the cell walls and permit the release of the cell protoplasm. The 

 whole mass was then subjected to a pressure of from 400 to 500 atmospheres. 

 The expressed liquor had a slightly acid reaction, it was weakly opalescent, 

 and contained albuminous material. It contained the active principle 

 which converts sugar into carbon dioxide and alcohol. Buchner calls it 

 zymase. It is very unstable, the filtered juice losing its activity after a 

 few days. The zymase is destroyed at 40-50 degrees. It can be dried, 

 and in this form keeps much better. It can also be precipitated from its 

 solution by the addition of alcohol or ether, 1 by which we obtain a white 

 powder, only partially soluble in water, but more so in glycerol. 2 The glycerol 

 extract is very active. Zymase has recently been obtained directly from 

 the yeast cell, by first killing the cell by contact with ether-alcohol or ether- 

 acetone. The zymase remains active after this treatment. Such prepa- 

 rations, which may be kept for a considerable time, are called preserved 

 yeasts. 



A vigorous objection was quickly raised against classifying zymase with 

 the unorganized ferments. Special attention was called to the fact that 

 the zymase in the expressed liquor was active only for a short time. This 

 was explained on the assumption that the zymase must be looked upon as 

 a part of the protoplasm, which, on being separated from the remainder 

 of the cell contents, possessed only a short period of activity. Quite aside 

 from the fact that it is now possible to prepare zymase with better keep- 

 ing qualities, this objection is met by what has been said above con- 

 cerning the cell ferments and their dependence upon their environment 

 and other ferments, etc. The expressed liquor contains not only zymase, 

 but also other ferments, of which one, the so-called endotryptase, quickly 

 destroys zymase. Zymase is, in fact, very susceptible towards proteolytic 

 ferments. It is also perfectly clear, that those ferments contained within 

 the cells would naturally be much more susceptible to unusual conditions 

 than those other ferments which are given off by the cells, and are undoubt- 

 edly better equipped for battle with the outer world. 



That, moreover, fermentation is not necessarily dependent upon living 

 cells, was already indicated by an observation of Fiechter, 3 who showed 

 that hydrocyanic acid completely arrests the vital processes of yeast, but 

 does not at once stop the fermentation. 



The tracing of the conversion of glucose to alcohol to a fermentation 

 process is not the only case where a so-called " life-process " has been 

 proved to take place independently of the living organism. Zymase, like 

 all other ferments, must be regarded as a product resulting from the life- 

 processes of the cells. The enigma of their formation and existence still 



1 R. Albert: Ibid. 33, 2775 (1900). 



2 R. Albert: Ibid. 36, 2375 (1902). 



3 Wirkung der Blausaure. Diss. Basel (1875). 



