A correspondent asks us to state in the Journal what is the so-called " Pasteur theory of fermentation." According to M. Pasteur, fermentation is a very common phenomenon; it is life without air, without free oxygen; and ferments, properly so-called, are organisms which easily accommodate themselves to this mode of life, - organisms independent of air, which grow at the expense of oxygen in combination with sugar. But moulds, generally living in the air, can themselves become ferments if they are compelled to vegetate without air. It also suffices to immerse saccharine fruits in carbonic acid gas to produde a spontaneous alcholic fermentation, by a kind of perversion of the chemical process of nutrition, which is afterwards kept up by means of oxygen of the sugar. The vegetable cellule, instead of elaborating sugar, lives upon that which exists in the fruit, and transforms it into alcohol. Grapes, Melons, Oranges, if confined under a bell-glass filled with carbonic acid, ferment at once, though no trace of yeast can be discovered in the pulp of these fruits. While Plums exposed to the air become very soft and sugary, the same Plums in carbonic acid gas become firm, hard, lose much sugar, and, if distilled, yield alcohol.

Hence there is every reason to believe that fermentation is nothing more than an example of nutrition by means of combined oxygen; but it must be added that free oxygen is necessary for commencing the fermentation by awakening the vital activity of the ferment. - Journal of Chemistry.