OSMOTIC EQUILIBRIUM 91 



inhibit its inverting action, for the former process can be 

 carried out in glucose solutions of great concentration, but 

 not in sucrose of similar strength. Thus solutions of 

 glucose were fermented even when containing over 70 

 per cent, of the sugar. 



As was pointed out previously, the yeast cell must be 

 permeable to sugars, so is not injured by such concentra- 

 tions. Bokorny found the upper limit for the carrying on 

 of fermentation by the yeast cell to be a 3' 7 normal 

 glucose solution, which possesses an osmotic pressure of 

 about 80 atmospheres. 



Euler and Palm ascertained that with the bottom yeast 

 they employed scarcely any plasmolysis took place inside 

 twenty hours in 15 per cent, mannitol. Glycerol of the 

 same concentration (not the same molecular concentra- 

 tion, however *) produced plasmolysis of the oldest cells 

 within fifteen minutes. .With 25 per cent, glycerol this 

 occurred almost instantaneously. Multiplication of the 

 cells took place in 15 but not in 20 per cent, glycerol. 



They also showed that a certain percentage only of the 

 cells were plasmolyzed after two hours in solutions of vari- 

 ous strengths. Each result is based on ten counts of plas- 

 molyzed and unplasmolyzed cells. The figures so obtained 

 are tabulated below and shown graphically in Fig. 5. 



TABLE XXVI. 



Percentage of Percentage of Yeast Cells 



Glycerol. plasmolyzed after Two Hours. 



10 17-1 



15 25-7 



20 38-4 



25 71-0 



* The molecular concentration of 15 per cent, glycerol is 1-66 per 

 litre; thit of 15 per cent, mannitol is only 0-82 per litre. 



