‘A wine ferment ... is not essentially different from a beer ferment, for both consist of membranous cells which are formed out of gum or vegetable mucilage. Both possess albuminous contents, which exude through the walls of the cells, and when brought into contact with sugar, cause it to ferment. These contents are soluble in water, more so in vegetable acids, and peculiarly so in tartaric acid. So much of the albuminous substance as is soluble is decomposed during fermentation, and more or less of its products must be contained in the liquid.’