Chapter III

. § 3 we were on our way to a solution of this question. It has been shown that fermentation cannot take place in the juice of crushed grapes if the must has not come into contact and been mixed with

## particles of dust on the surface of the grapes, or of the woody part of

the bunch. It would, however, be sufficient that a vintage vat, of any capacity whatsoever, should receive the particles of dust existing on a single bunch in some cases, on even a single grape, for the whole mass to enter into fermentation.

[Illustration: Plate 8. Fertile Mould-cells from the Outer Surface of Grapes.]

What, then, we must ask ourselves, is the nature of these particles of dust? On September 27th, 1872, we picked from a vine, in the neighbourhood of Arbois, a bunch of grapes, of the variety called _le noirin_. The bunch selected, without any injury to a single grape, was brought to our laboratory in a sheet of paper that had been previously scorched in the flame of a spirit lamp, and the grapes were cut off with a pair of fine scissors, which had also been passed through the flame. By means of a badger-hair brush, thoroughly purified in water, each grape to which a portion of its peduncle remained attached, was washed in a little pure water. The successive washing of a dozen grapes in 3 c.c. of water was sufficient to make the water turbid; we then examined it under the microscope. Each field contained many little organized bodies, accidentally associated, now and again, with some very scarce crystalline spicules. As a rule, the organisms consisted of simple, transparent, colourless cells; some, indeed, of larger size had a yellowish brown colour, and were detached or united in irregular masses; and, lastly, there were club-shaped or bottle-shaped vessels, full of spores ready to germinate. We repeated this experiment with bunches of other varieties of grape, and also submitted to examination water in which the outer surfaces of gooseberries, plums, and pears had been washed; the result was in each case the same, that is, we found a great number of the same colourless cells, and the same irregular masses of darker cells, which latter, however, we must not confound with the masses of dead cells sometimes found covering parts of the epidermis of certain fruits.

As we had purposely left each fruit attached to part of its peduncle, we wished to ascertain if these corpuscles proceeded from the grapes or from the wood of the peduncle. For this purpose we washed separately the surface of the grapes and the woody part of the bunch. The water in which the latter was washed was visibly more charged with the minute organisms than that in which the grapes was washed, although the latter was by no means free from them.

Plate VIII. represents these corpuscles as they exist on the surface of fruits, magnified 500 times. The groups, _b_, _b_, _b_, ..., _c_, _c_, ... are of a brown colour, more or less dark, or of a reddish yellow; the cells _a_, _a_, ... are transparent. Amongst them are some spores of ordinary fungoid growths, and several cells which are probably the issue of a germination that had commenced in certain groups which have a hard, yellowish appearance, and which are provided with what seems to be a double case—_b_, _b_, _b_, ..., _c_, _c_, ..., a result of the moisture of the woody part of the bunch, or of rain that fell just before the commencement of our observations.

It is an easy matter to trace the germination of these different varieties of cells with the microscope. We put a drop of the water in which the woody part of a bunch of grapes has been washed into a small quantity of wort, previously boiled and filtered bright. Plate IX. presents a series of developments observed in the case of simple or grouped cells, A, D, G, and J. The process is as follows: The yellowish-brown cells soften and grow larger in the nutritive medium, and gradually become almost transparent and colourless. At the same time we see some very young buds appear on their margins; these rapidly increase in size, and detaching themselves to make room for others, move off as young cells that after a time bud in their turn. The rapidity with which these cells bud and multiply is often extraordinary. The group A and the cell D produced the groups C and F within twenty-four hours, passing through the intermediate stages represented in groups B, E. The cells A and D did not give rise to any filamentous growths, at least whilst under our observation. Some groups of cells, however, put forth, from the first, long filaments, having cross-partitions and resembling the mycelium in ordinary fungoid growths. Together with these, and along their whole length, was an abundance of cells, often in clusters, as represented by Fig. G, the whole of which growth took place in less than twenty-four hours.[86] But apart from contact with the air, there was a complete absence of life.

[Illustration: Plate 9. Various Examples of the Mode of Growth of Mould-cells from the Outer Surface of Grapes.]

The figures H, I, J, K, represent other aspects of developing cells and filaments. The cells H are spherical; the cells I have numerous buds, as also have those marked K. These different forms were all produced in the course of twenty-four hours by the cell which may be observed in the centre of the group J. In connection with this same group, J, we may remark that on September 30, 1872, at 10 A.M., we witnessed the detachment of three oval cells at the points _a_, _b_, _c_; by 10.45 other buds of the size represented in our engraving had formed in their place; by about five o’clock that same afternoon these buds, _a_, _b_, _c_, having become transformed into cells, fell off in their turn.[87]

It may be asked, what proof have we that amongst the filamentous and cellular growths which spring from the small, dark bodies existing in the particles of dust adhering to the surface of fruits, and which we here see bud and multiply with such marvellous rapidity, the ferment or ferments of vintage do actually exist? A very simple experiment will prove conclusively that this is the case. When in the course of twenty-four or forty-eight hours, by contact with saccharine must, and in presence of excess of air, the revival and development of the cells has taken place on the bottom of the little troughs employed in our observations; if then we fill up the trough with the same must, so that there remains no free air under the cover-glass, within a very short time—an hour, half-an-hour, or often less—we shall see bubbles of gas rise from the bottom, accompanied by an increase in the deposit of cells. This will be the must fermenting after the submersion of the cellular plants. It follows that the cells, or groups of cells, of a dark colour which cover the grapes, or the woody part of the clusters, are actual germs of the cells of yeast; more correctly speaking, that germs of yeast-cells exist amongst these groups, for it would not be consistent with truth to say that the various germinating forms present in the dust on the surface of grapes must all of them give rise to actual corresponding ferments. Thus the flask-shaped spores _c_, _c_, ... in Plate VIII., are reproductive organs of _alternaria tenuis_, which have probably nothing in common with alcoholic ferment or ferments, properly so called, except their outward form. We may repeat, however, and it is a point of great importance to bear in mind, that the cells of yeast originate from some or other of the little, brownish, organized bodies, which the microscope reveals in such numbers amongst the particles of dust existing on the surface of fruits.

The impossibility, which we have already demonstrated (