ALCOHOLIC FERMENTATION OF SUGAR 137 



sand and 250 grams of infusorial earth generally known as 

 Kieselguhr, and the mixture was ground together till plastic 

 and damp ; 100 grams of water were added to the mixture, and 

 it was then wrapped up in a press cloth and put in a filter press 

 capable of exerting a pressure of 400 to 500 atmospheres. 

 About 300 c.c. of juice were thus obtained. The remaining 

 cake was ground up again, sieved, and another 100 c.c. of 

 water added ; on again pressing a further 150 c.c. of juice were 

 obtained. The whole volume of juice was clarified by shaking 

 with Kieselguhr and filtering. 



Thus prepared, the juice is a clear opalescent liquid of a 

 pleasant yeast smell, with a specific gravity at 17 C. of 

 T0416. On boiling, a quantity of albuminoid matter separates 

 and the liquid becomes nearly solid. 



If the unboiled juice is mixed with an equal volume of con- 

 centrated cane sugar solution, an evolution of carbon dioxide 

 begins after a period varying from a quarter of an hour to an 

 hour, and the evolution continues for about twenty-four hours. 



Similar results are obtained from grape sugar and from 

 fructose, but not from lactose or mannitol ; this corresponds 

 with the activity of the living yeast. Every precaution was 

 taken to work aseptically, and no yeast cells could be found on 

 microscopical examination of the liquid. Moreover, the action 

 is not stopped by chloroform, nor by passage of the liquid 

 through a Berkefeld filter or through a dialysing membrane. 

 Hydrocyanic acid stops the action, but this recommences if 

 air is passed through to drive off the HCN, showing that the 

 effect of the latter is not due to the poisoning of the living 

 organism, but more probably to the formation of a loose com- 

 pound between HCN and the enzyme. 



The fermentation is a true alcoholic fermentation in that 

 alcohol and C0 2 are produced in the same proportion as when 

 living yeast is used; by-products such as succinic acid 

 and glycerine are also produced. The enzyme which is 

 present in the solution has been termed by Buchner zymase. 



