The sketch was made directly after the fermentation had commenced. Probably this is simply one of the earlier forms assumed by the _saccharomyces_, or by one of its varieties. It will be seen that the alcoholic ferment is associated with another little filiform ferment, probably the lactic. The spontaneous ferments are almost always impure, a circumstance that may be readily understood if we bear in mind the results described in Chapters III. and IV. § III.—On “High” and “Low” Ferments. The ferments mentioned in the preceding paragraphs do not belong, properly speaking, to industrial products; that is to say, in actual practice there are no operations in which the ferments of fruits and spontaneous ferments are employed for the purpose. It is quite true that these ferments are the cause of the fermentations from which wine, cider, gin, rum, gentiana, mead, &c., are derived, but these fermentations are spontaneous, they take place without the intervention of man, and without man’s directing their production, or taking any notice of the agent which starts them. In the manufacture of beer, on the other hand, the practice is quite different. We may say that the wort is never left to ferment spontaneously, the fermentation being invariably produced by the addition of yeast formed on the spot in a preceding operation, or procured from some other working brewery, which, again, had at some time been supplied from a third brewery, which itself had derived it from another, and so on, as far back as the oldest brewery that can be imagined. A brewer never prepares his own yeast. We have already had occasion to remark that the interchange of yeasts amongst breweries is a time-honoured custom, which has been observed in all countries at all periods, as far back as we can trace the history of brewing. The yeasts which in the present day produce beer in the brewery of Tourtel, near Nancy, in that of Grüber, at Strasburg, that of Dreher, at Vienna, and others, came originally from breweries, where and when it would be hard to say. In the case of the first working brewery, the yeast was, no doubt, derived from some spontaneous fermentation, which took place in an infusion of barley that had been left to itself, or, from some natural spontaneous ferment, and nothing could be easier than to realize this fact again. In the brewing industry there are two distinct modes of fermentation:—“high” fermentation and “low” fermentation, some of the distinctive characteristics of which we have pointed out in Chapter I. It may be questioned whether the spontaneous yeast employed in the first brewery, or that which a wort left to itself in the present day would yield, would be of the “high” or “low” type. It may be concluded from what we have said on the subject of spontaneous fermentations in wort, that wort, left to itself, would furnish ferments more or less resembling those of wine. We have never obtained in spontaneous