Putrefaction

Putrefaction is the term given to the decomposition of organic substances when accompanied by an offensive smell. It was long supposed to be ordinary chemical change due to the complexity, resulting instability, and affinity for oxygen of organic matter. It is now known to be the result of the living activity of certain minute plants called Bacteria (q.v.), which also cause Fermentation (q.v.) and many diseases (see GERM). The spores of these plants are present in great numbers in the lower levels of the air, in water, and on the surface of the earth; and, as they are only about .001 mm. in diameter and two to four times as long, it is not surprising that they were not seen, and that putrefaction was supposed to be spontaneous. But, if we boil an infusion of organic stuff and so kill the bacteria in it, and, while the steam is coming freely off, close it up with a plug of cotton wool, which, while allowing free access to air, prevents any germs or spores from reaching the fluid, it will remain without any change for years, but will begin to putrefy in a day or two if the plug be removed. A low temperature, although it will not kill the bacteria, will stop their growth and the resulting destructive changes; hence the use of freezing food on shipboard. Salicylic, carbolic, and other acids also check growth, but there seem to be only a few poisons, such as corrosive sublimate, chlorine, and bromine, that actually kill. Drying stops growth and kills the developed plant, in a few days, but the spores will live for a long time in a dried condition. The effect of oxygen is various: some species require it, while others are hindered in their growth by it; and a high pressure of oxygen will kill even those kinds that need a certain amount in a few days. Of the precise chemical changes that take place as a result of the life of bacteria we are still largely ignorant; the chief final results of these changes are described under FERMENTATION. For an investigation in the causes of putrefaction, see Tyndall's Floating Matter of the Air (1881).