364 



LOUIS PASTEUR 



is capable of bringing about the fermentation of a pure 

 solution of sugar. It is manifest to any one who has 

 studied such fermentation with the microscope, even in 

 those cases where the sweetened water has been absolutely 

 pure, that ferment-cells do multiply, the reason being that 

 the cells carry with them all the food-supplies necessary 

 for the life of the ferment. They may be observed bud- 

 ding, at least many of them, and there can be no doubt 

 that those which do not bud still continue to live; life has 

 othec ways of manifesting itself besides development and 

 cell-proliferation. 



If we refer to the figures on page 81 of our Memoir of 

 1860, Experiments D, E, F, H, I, we shall see that the 

 weight of yeast, in the case of the fermentation of a pure 

 solution of sugar, undergoes a considerable increase, even 

 without taking into account the fact that the sugared 

 water gains from the yeast certain soluble parts, since in 

 the experiments just mentioned, the weights of solid yeast, 

 washed and dried at 100 C. (212 F.), are much greater 

 than those of the raw yeast employed, dried at the same 

 temperature. 



In these experiments we employed the following weights 

 of yeast, expressed in grammes (i gramme= 15.43 grains): 



(O 2.313 



(2) 2.626 



(3) 1-198 



(4) 0.699 

 Cs) 0.326 

 (6) 0.476 



which became, after fermentation, we repeat, without 

 taking into account the matters which the sugared water 

 gained from the yeast: 



grammes. grains. 



(1) 2.486 Increase 0.173 = 2.65 



(2) 2.963 0.337 = 5-i6 



(3) 1-700 0.502 = 7-7 



(4) 0.712 0.013 = 0.2 



(5) 0.335 0.009 = 0.14 



(6) 0.590 0.114 = 1.75 



Have we not in this marked increase in weight a proof 

 of life, or, to adopt an expression which may be preferred, 



