1. Temperature.—Putrefaction advances most rapidly at a temperature between 70° and 100° F. It may commence at any temperature above 50° F., but it is wholly arrested at 32° F. So one day’s exposure of a body in summer may effect greater changes than one week in winter. After freezing, putrefaction takes place with unusual rapidity upon the thawing out of the body. A temperature of 212° F. stops all putrefactive changes.
2. Moisture.—Putrefaction takes place only in the presence of moisture. An excess of moisture, however, seems to retard the process, possibly by cutting off the excess of air. The viscera according to the amount of water they contain decompose at different times after death—for instance, the brain and eye rapidly, the bones and hair slowly.
3. Air.—Exposure to air favors decomposition by carrying to the body the micro-organisms which bring about putrefaction; absence of air soon arrests the changes: this is seen in bodies hermetically sealed in lead coffins, which remain unchanged for a long period of time. Moist rather than dry air favors putrefaction by lessening evaporation. Air in motion retards while still air favors the change.
It is to be remembered that a body decomposes more rapidly in air than in water or after burial. Given similar temperatures, the amount of putrefaction observed in a body dead one week and exposed to the air will about correspond to one submerged in water for two weeks or buried in a deep grave for eight weeks.
4. Age.—The bodies of children decompose much more rapidly than those of adults; fœtuses still more rapidly. Aged bodies decompose slowly, probably on account of a deficiency of moisture. Fat and flabby bodies decompose quickly for the same reason.
5. Cause of Death.—In cases of sudden death, as from accident or violence, the body decomposes more rapidly than when death results from disease. Putrefaction sets in early in death from the infectious fevers, such as typhus, pyæmia, and typhoid fever, also in death from suffocation by smoke or coal gas, by strangulation or after narcotic poisoning. Those parts of a body which are the seat of bruises, wounds, or fractures, decompose rapidly; this is especially seen in parts after a surgical operation.
6. Manner of Burial.—When a body is buried in low ground in a damp, swampy, clay soil, decomposition advances rapidly, as also when the grave is shallow so the body can be exposed to constant variations of temperature. A porous soil impregnated with animal and vegetable matter favors putrefaction, as also burying a body without clothes or coffin; this is especially seen where infants have been thrown into the ground and loosely covered with earth.
Circumstances Retarding Putrefaction.
1. The Temperature.—Below 32° F. and above 212° F. putrefaction is entirely arrested. The rapidity of the change considerably lessens as the temperature advances above 100° F. A remarkable instance of the preservative power of cold is given by Adolph Erman, who states that the body of Prince Menschikoff, a favorite of Peter the Great, exhumed after ninety-two years’ burial in frozen soil, had undergone hardly any change. Buried in hot sand as is seen in the desert, a body putrefies very slowly and generally becomes mummified.
2. Moisture.—Absence of moisture retards decomposition. In the dry air of the desert bodies have been preserved for a long period of time.