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The process of fermentation, which has for its object either the manufacture of bread, or of an alcoholic product in a more or less concentrated form, is very similar in action during its earlier stages. It commences with the growth and multiplication of the fermenting germs contained in the minute organisms floating in the air, the inorganic constituents of the water, and the protoplasm (essence of life) of the yeast; and all the changes brought about are accompanied by heat. Fermentation is caused by the decomposition of the starch and gluten of a solution of either potatoes, flour, or malted barley, which decomposition is accompanied by an evolution of gas. There is also a peculiar vibration given to the various bodies in contact, which agitates the whole. This agitation is increased by the bursting of the starch-cells and the formation therefrom of maltose, and also by the changing of the maltose sugar into carbonic acid gas. Substances in a state of decomposition are capable of bringing about a change in the chemical composition of bodies with which they are in contact. Most of the vegetable substances used in fermentation have a constituent part—sugar, starch, or some other substance—which is easily converted into a fermentable sugar by the action of yeast, or of diluted mineral acids, or by a constituent of malted barley, called diastase. The sugar produced by these means is resolved into carbonic acid gas and alcohol by vinous fermentation. It will be seen, therefore, that fermentation is started by the saccharine element in the ferment, which is termed maltose; the process is then kept up by the gluten, which, becoming decomposed, aids the sugar and starch in the work of providing food for the yeast as soon as the latter is brought in contact with it. The fermentation then takes place very rapidly, and carbonic acid gas is generated and given off in proportion to the amount of the products contained in the ferment, or sponge, and also to the strength and freshness of the yeast: especially is this so with gluten, which is the great agent of fermentation, when in a state of decomposition and when in contact with yeast.