We have remarked elsewhere that the pains devoted to the rearing of vines, and to the ordinary operations of vinification, such as _ouillage_,[3] sulphuring, and repeated rackings, as well as the use of cellars and vessels hermetically closed, are entailed by the necessity of counteracting and preventing the diseases to which wine is liable. The same may be said, _a fortiori_, of beer, inasmuch as it is more liable to change than wine. Manufacturers and retailers of this beverage have to strive constantly with the difficulty of preserving it, or the wort used in its manufacture. We may readily be convinced of this by reviewing the usual processes of the art of brewing. When the infusion of malt and hops, which is termed wort, is completed, it is left to cool. It is next put into one or more casks or vats, in which it is made to undergo alcoholic fermentation—the most important of all the processes in brewing. The cooling must be as rapid as possible. This is a condition of success; otherwise, the wort may deteriorate, which will necessarily lead to deterioration in the quality of the beer. As long as the wort is at a high temperature it will remain sound; when under 70° C. (158° F.), and particularly when at a temperature of from 25° C. to 35° C. (77° F. to 95° F), it will be quickly invaded by lactic and butyric ferments. Rapidity in cooling is so essential that to secure it recourse is had to special apparatus.[4] Even in the preparation of wort, especially when it is effected by successive mashings, in summer, deterioration is imminent: in fact, it is not rare to see the wort becoming acid during the _mashes_, if these are not accomplished with all possible celerity. After the wort has been cooled, it is mixed with yeast. This is obtained from a previous fermentation, and, after being thoroughly pressed, is added at the rate of from one to two thousandth parts of the weight of the wort, that is, from 100 to 200 grammes per hectolitre (about 4 oz. to 8 oz. average for every 25 gallons). At first sight, this yeast seems free from the possible diseases of the wort and beer; but this is by no means the case. Now, why do we add yeast to our wort? This practice is unknown in the art of vinification. The must is always left to spontaneous fermentation. Why should we not leave the wort to operate in the same manner?