372 



Dr. A. Harden and Mr. W. J. Young. [June 14, 



The cessation of fermentation in any particular mixture of inactive 

 residue and coferment may, therefore, be due to the disappearance either 

 of ferment or coferment from the liquid. If the amount of coferment 

 present be relatively small, it is the first to disappear, and fermentation can 

 then only be renewed by the addition of a further quantity, whilst the 

 addition of more ferment produces no effect. If, on the other hand, the 

 amount of coferment be relatively large, the inverse is true ; the ferment 

 is the first to disappear, and fermentation can only be renewed by the 

 addition of more ferment, a further quantity of coferment producing no 

 effect. This is illustrated by the following experiment made at 26° : — 



Two solutions were made up, each containing 05 gramme of dry inactive 

 residue +10 c.c. of 10-per-cent. glucose solution and toluene, and to each of 

 these 2 c.c. of boiled juice containing 10 per cent, glucose were added. As 

 soon as fermentation had ceased, - 5 gramme of dry residue in 10 c.c. of 

 glucose solution was added to one solution (a), and 2 c.c. of boiled juice 

 diluted to 10 c.c. with glucose solution to the other (b). Two other solutions 

 were also prepared, each containing 0'4 gramme of the same dry inactive 

 residue +10 c.c. of 10-per-cent. glucose solution + toluene, and 25 c.c. of the 

 same boiled juice containing glucose were added to each. 



As soon as fermentation had ceased, - 4 gramme of residue dissolved in 

 10 c.c. of glucose solution was added to one (c), and 10 c.c. of boiled juice 

 containing glucose to the other (d). The following were the results : — 





Boiled juice 

 added. 



Fermentation 

 produced. 



Subsequent addition. 



Additional 

 fermentation. 





C;C. • 



c.c. 





c.c. 



(«) 



2 



9-4 



- 5 gr. residue 







(6) 



2 



7-6 



2 c.c. boiled juice 



8-9 



(c) 



25 



56 -8 



O '4 gr. residue 



36 -8 



(<*) 



25 



50 



10 c.c. boiled juice 







(3) Bate of Disappearance of the Coferment from, Yeast-juice. 



The following experiments were made to ascertain approximately the rate 

 at which the coferment disappears from yeast-juice both in the absence and 

 presence of added glucose. For this purpose a quantity of yeast-juice was 

 preserved at 25° in presence of toluene, and samples were removed, boiled and 

 filtered, at the commencement of the incubation and after various intervals. 

 In one case a parallel experiment was made with yeast-juice to which 

 10 grammes of glucose per 100 c.c. had been added. The filtrates were then 

 all rendered neutral to litmus and tested with equal quantities of an inactive 



