Thus in the destruction of that which has lived, all reduces itself to the simultaneous action of these three great natural phenomena--fermentation, putrefaction, and slow combustion. A living organism dies--animal, or plant, or the remains of one or the other. It is exposed to the contact of the air. To the life which has quitted it succeeds life under other forms. In the superficial parts, which the air can reach, the germs of the infinitely small aérobies hatch and multiply themselves. The carbon, the hydrogen, and the nitrogen of the organic matters are transformed by the oxygen of the air, and under the influence of the life of these aérobies, into carbonic acid, vapour of water, and ammonia gas. As long as organic matter and air are present, these combustions will continue. While these superficial combustions are going on, fermentation and putrefaction are doing their work in the interior of the mass by the developed germs of the anaérobies, which not only do not require oxygen for their life, but which oxygen actually kills. Little by little, at length, by this work of fermentation and slow combustion, the phenomenon is accomplished. Whether in the free atmosphere, or under the earth, which is always more or less impregnated with air, all animal and vegetable matters end by disappearing. To arrest these phenomena an extremely low temperature is required. It is thus that in the ice of the Polar regions antediluvian elephants have been found perfectly intact. The microscopic organisms could not live in so cold a temperature. These facts still further strengthen all the new ideas as to the important part performed by these infinitely small organisms, which are, in fact, the masters of the world. If we could suppress their work, which is always going on, the surface of the globe, encumbered with organic matters, would soon become uninhabitable. FOOTNOTE: [8] [A millimeter is 1/25th of an inch.] _ACETIC FERMENTATION._ THE MANUFACTURE OF VINEGAR. Soon afterwards Pasteur came upon a most curious illustration of the 'fixation' of atmospheric oxygen by a microscopic organism--the transformation of wine into vinegar. As its name indicates, vinegar is nothing else than wine turned sour. Everybody has remarked that wine, left to itself, in circumstances which occur daily, is frequently transformed into vinegar. This is noticed more particularly when bottles, having been uncorked, are left in a half-empty condition. Sometimes, however, wine turns sour even in corked bottles. In this case we may be sure that the bottles have been standing upright, and that corks more or less defective have permitted the air to penetrate into the wine. The presence of air, in fact, is indispensable to the chemical act of transforming wine into vinegar. How does this air intervene? And what is the little microscopic creature which, in conjunction with the air, becomes the agent of this fermentation?