256 NATURE AND LIFE. 
years by several men of science, among whom in the first 
rank Pasteur is to be cited. 
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 exposed to the air, the 
more or less rapid production of alcohol is always con- 
nected with the production of a microscopic fungus, consist- 
ing 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 ex- 
changes of growth they give rise to, produce decomposi- 
tion of the sugar into alcohol and carbonic, succinic, and 
glyceric acids. These are the four invariable products of 
alcoholic fermentation. Sugar is the food of the yeast-fun- 
gus; these products are its excretions. 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. 
Dumas, who signalized his entrance upon the career of 
studies in natural science half a century ago, by memo- 
rable discoveries in microscopic physiology, has lately re- 
turned to researches of the same kind, precisely, in respect 
to fermentations. In Pasteur’s laboratory at the Normal 
School he has taken up investigations on this subject, the 
results of which, quite lately published, show that the dis- 
tinguished savant in question has lost neither his cautious 
diligence in experimental processes, nor his lucid concep- 
tion in the grasp of principles. He has attempted, among 
other things, to determine the decomposing force, the 
amount of activity, possessed by each cell of the alcoholic 
