56 LOUIS PASTEUR. 



more extraordinary than it did in the deep vats. The 

 life of the ferment is itself singularly enhanced, but 

 the proportion of the weight of the decomposed sugar 

 to that of the yeast formed is absolutely different in 

 the two cases. While, for example, in the deep vats, 

 a kilogram of ferment sometimes decomposes seventy, 

 eighty, one hundred, or even one hundred and fifty 

 kilograms of sugar, in the shallow troughs one kilo- 

 gram of the ferment will be found to correspond to 

 only five or six kilograms of decomposed sugar. These 

 proportions between the weight of the sugar which 

 ferments and the weight of the ferment produced, 

 constitute the measure of what one might call the 

 ferment's character of that character which distin- 

 guishes its mode of life from that of all other existences, 

 great or small, in which the weight of the organising 

 matter and the assimilated alimentary matter are about 

 equal. In other words, the more free oxygen the yeast 

 ferment consumes, the less is its power as a ferment. 

 Such is the case in the shallow troughs where the 

 extended surface is exposed to the contact of the 

 oxygen of the air. The more, on the contrary, the 

 life of the ferment is carried on without the presence of 

 free oxygen, the greater is its power of decomposing and 

 of fermenting the saccharine matter. This is the case 

 in deep casks. The intimate co-relation then between 

 life without air and fermentation appears complete. 

 The unexpected light which' these facts threw upon 



