FERMENTS. FERMENTATIONS. AND LIFE. 543 



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ale. In the first few years of this century Turpin, and afterward Cagni- 

 ard-Latour, attempted in vain to prove that such a relation existed; 

 it was always denied that any thing else could be observed in alcoholic 

 fermentation than an operation resembling all those slow decomposi- 

 tions that were classed among fermentations. We have admitted, in 

 our time, that alcoholic fermentation, instead of being an exception, is 

 on the contrary the very type of the phenomena we are treating of; that 

 the yeast-cells, far from being unimportant, take an essential part in 

 it, and that in all fermentations whatever there occur low organiza- 

 tions, microscopic corpuscles, more or less analogous to those of yeast. 

 At least this is the first result of investigations carried on in the past fif- 

 teen years by several men of science, among whom in the first rank 

 M. Pasteur is to be cited. 



M. Pasteur began the course of his labors in 1858, by the study of 

 alcoholic fermentation. He placed it beyond a doubt that, in the case 

 of grape-juice or beer-wort, as in that of any other saccharine liquid ex- 

 posed to the air, the more or less rapid production of alcohol is always 

 connected with the production of a microscopic fungus, consisting of 

 rounded globules, a few thousandths of a millimetre in diameter. 

 These globules, known under the name of brewer's yeast, multiply in 

 the fermenting liquid at the expense of the organic matters it contains, 

 and, by the exchanges of growth they give rise to, produce decompo- 

 sition of the sugar into alcohol and carbonic, succinic, and glyceric 

 acids. These are the four invariable products of alcoholic fermenta- 

 tion. Sugar is the food of the yeast-fungus ; these products are its ex- 

 cretions. The laws of the inner mechanism that elaborates them are 

 yet unknown. But every thing leads us to believe that the yeast-cells 

 secrete a substance more or less resembling those that work out the 

 phenomena of digestion in the higher animals. Alcoholic fermentation 

 would thus be a kind of digestion of sugar within the globule. 



M. Dumas, who signalized his entrance upon the career of studies 

 in natural science half a century ago, by memorable discoveries in 

 microscopic physiology, has lately returned to researches of the same 

 kind, precisely, in respect to fermentations. In M. Pasteur's labora- 

 tory at the Xormal School he has taken up investigations on this sub- 

 ject, the results of which, quite lately published, show that the distin- 

 guished savant in question has lost neither his cautious diligence in 

 experimental processes, nor his lucid conception in the grasp of princi- 

 ples. He has attempted among other things to determine the decom- 

 posing force, the amount of activity, possessed by each cell of the alco- 

 holic ferment. To ascertain this, he measured the quantity of sugar 

 decomposed in a given time by a fixed weight of yeast, and he found 

 — after first establishing that a cubic millimetre of yeast contains about 

 2,772,000 cells — that the power of a million of cells represents the force 

 capable of decomposing four grains of sugar in an hour. If we attempt- 

 ed according to this estimate to express in figures the number of cells 



