Page:Popular Science Monthly Volume 7.djvu/737

This page has been validated.
PASTEUR ON FERMENTATION.
717

gen, all the oxygen of the original sugar, are now in suspension in the air in the gaseous state, ready to be borne away by the winds-and again to enter into the cycle of life under the influence of the beneficent heat of the sun. It is here that I would place the providential idea, not sentimentally only, this time, but by a real and serious scientific deduction, and because it seems to me that we have seized one of the great laws of Nature.

Let us return a little upon our steps and see where we are. What is the condition of our liquid mass? It is now only water holding in solution a very small quantity of mineral or organic substances. Evaporation would promptly reduce the whole mass to the deposit of which I spoke a moment ago, and which is lying at the bottom of the vessel, the wine-yeast, the vinegar-yeast in two portions, that which formed the vinegar and that which destroyed it, together with the stems and skins of the grapes.

What is going to take place in this liquid mass, no longer acid, but neutral now, in which there is held in solution only a little mineral and nitrogenized matter, which, it is true, is always ready to be renewed, at least for a long time, by the help of the materials at the bottom, which, thus far, have undergone nothing but simple maceration?

Pressed for time, I was only able at our last meeting to begin my answer to M. Bouillaud, and to do that even in terms so far removed from the subject that you must have found it difficult to understand the connection of the phenomena then described with the real object of the question. This connection, prepared by what has preceded, will now seem very clear.

Have we not reached a point in the succession of the grand natural phenomena which I am passing in review, at which we have to deal with a liquid of absolutely the same kind as that which I showed you at our last meeting, and one which is even more suitable for the phenomena of putrefaction of which I then spoke? If the liquid of our great reservoir is now formed of distilled water, phosphates, chlorides, and sulphates, there is at the bottom, to replace the lactate of lime of last Tuesday's experiment, a collection of carbonized or nitrogenized substances much better fitted than lactic acid to supply the carbonic food suitable for the development of the vibrios.

And, in fact, scarcely has the last mycodermic pellicle fallen to the bottom, scarcely have a new death and a new quiet fallen upon our liquid, scarcely has it lost all acidity, when, little by little, it becomes cloudy throughout; germs floating in the air have brought to it a new life, not one like those which you have seen precede it, but another, one rendered possible by the neutral character of the new liquid. The whole surface becomes covered by a layer of fatty, mucilaginous aspect. In the deeper portions, throughout the whole mass, as I said, we see a milky cloudiness; at the same time an infectious and very deleterious odor announces, even at a distance, the putrefaction and