102 PHYSIOLOGY OF YEASTS 



quency of the formation of alcohol in living tissue. We have seen 

 that alcoholic fermentation is not a phenomenon exclusive to the yeast 

 but is met among most fungi and also in tissues containing sugar. 

 Alcohol seems to be rather frequently produced in cells. Berthelot, 

 Devaux, and Maze have found alcohol in a great number of plants 

 placed under normal conditions. Bechamp has isolated alcohol from 

 the brains of sheep. 



Therefore, from these contributions, certain authors think (Wort- 

 mann, Polszeniuz, Goldewski, Maze l and Duclaux, Pfeffer, Palla- 

 dinn, 2 Stoklasa, etc.) that zymase exists in all organisms and func- 

 tions in the usual manner. For these investigators, alcohol is always 

 an intermediate product in respiration of plants and animals. Res- 

 piration, according to this, is made up of two phases. In the first, or 

 intramolecular respiration, there is no need of concourse with oxygen; 

 the sugar is decomposed into alcohol and carbon dioxide by zymase. 

 This is intramolecular respiration or alcoholic fermentation. In the 

 second phase, the alcohol, thus formed, will be changed in the pres- 

 ence of air by means of oxidase into carbon dioxide and water. 

 This is respiration, properly speaking, or external respiration. In the 

 absence of air, the phenomenon will stop with the formation of al- 

 cohol. 



Thus, to express this theory with formulae, the zymase would 

 accomplish the following: 



C 6 Hi 2 6 = 2 C 2 H 6 O + 2 CO 2 . 



The second phase which takes place in contact with air is as follows: 

 C 2 H 6 O + 3 O 2 = 2 C0 2 + 3 H 2 O. 



In case that an organism, or yeast, finds itself away from air the 

 change will stop at the first stage. As it goes on with much inten- 

 sity, it will give sufficient energy for those organisms which are able 

 to live without air like the yeasts. One finds here, then, a point of 

 departure from Pasteur's theory. 



Other authors go farther. They admit that alcohol is not only 

 a product of respiration, but also term it a more simple assimilation 

 of carbon. The hydrocarbon elements may then be transformed into 

 alcohol before being assimilated. According to this, the hexoses which 

 are formed from the polysaccharides by the various enzymes will be 

 changed into alcohol by the zymase. If the phenomenon takes place 

 in contact with air, a part of the alcohol is oxidized by the oxidase, 



1 Maze, P. La respiration des plantes vertes; theorie biochimique et theorie 

 de la zymase. Rev. g. des sciences, 1906. No. 17. 



2 Palladinn, W. Sur la respiration des plantes. Biochem. Zeitschr. 18, 1909. 



