I. In the month of October, 1873, we procured from a vineyard in the canton of Arbois some of the woody parts of very ripe clusters of grapes, taking the precaution to cut off all the grapes, one by one, with a very clean pair of scissors, whilst still on the vine; we then wrapped up the woody parts of the clusters, thus deprived of their grapes, in thin paper, to convey them to Paris. Our only object at that time was to secure for use in our subsequent studies the ferment-bearing dust found in October on the woody part of the vine, and, more particularly, on the clusters themselves, as already stated. After our return to Paris, and during the course of our experiments in October and November, it sufficed to wash a few scraps of the bunches in a little pure water, in order to obtain the grape-ferment in abundance; but later on in the winter we were astonished to find that the same procedure yielded no ferment, only some moulds. The bunches which, when put into boiled and filtered must, in October, very readily caused that must to ferment, at the end of winter could no longer produce the same effect, however favourable might be the temperature to which we raised the must. The particles of dust on the bunches had, therefore, become sterile, as sources of alcoholic ferments. II. On February 17th, 1875, we purchased of Chevet, a dealer in provisions, two bunches of white grapes, which were perfectly sound, presenting not the slightest trace of injury or bruise. We took an iron pot full of mercury, which had been heated to 200° C. (392° F.), and then covered over its surface with a sheet of paper that had also been subjected to flame. When the mercury had cooled down we placed several of Chevet’s grapes, singly and in small bunches, on the surface of the metal, and, after having enclosed them in a glass cylinder that had been previously heated with and by means of the mercury, we crushed them in this vessel, in contact with air, by means of a strong, crooked iron wire that had been passed through the flame of a spirit lamp. The object of all these precautions was to prevent any cause of error, such as might have resulted from the accession of particles of dust associated with the mercury, or floating about our laboratory. We then placed our cylindrical jar in an oven, at a temperature of 25° C. (77° F.); but though the experiment was continued for several days following, no fermentation manifested itself. At last, to assure ourselves that the pulp and liquid were, notwithstanding this, well adapted to fermentation, we introduced into the test-flask an almost imperceptible quantity of yeast. This readily developed, and promptly produced fermentation.[91] It seems possible, therefore, that the germs of ferment may not exist on bunches of sound grapes during winter, and that the well-known experiment of Gay-Lussac on the influence of air on the fermentation of the must of crushed grapes cannot succeed at all times.