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Pallor mortis |
Putrefaction is one of seven stages in the decomposition of the body of a dead animal. It can be viewed, in broad terms, as the decomposition of proteins, in a process that results in the eventual breakdown of cohesion between tissues and the liquefaction of most organs.
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In terms of thermodynamics, all organic tissue is a stored source of chemical energy and when not maintained by the constant biochemical efforts of the living organism it will break down into simpler products. The breakdown of proteins in a decomposing carcass is a spontaneous process but one that is accelerated as the anaerobic microorganisms, already present in the animal's digestive tract when it was alive, consume and digest the proteins that comprise the creature's cells. As cells and their proteins are digested, the tissues of the body are left in a weakened state. Proteins are broken down into smaller components and these are excreted by the bacteria. The excreted components, which include gases and amines such as putrescine and cadaverine, give rise to the putrid odor associated with a decomposing body. The gases are initially constrained within the body cavities but diffuse though adjacent tissues and into the circulatory system. Once within the blood vessels, the gases will then spread to other parts of the body. The result is macroscopically visible bloating of the torso and then the limbs. The increased internal pressure due to the increased volume of gas also helps to weaken and separate tissues. In the end some part of the body will rupture, releasing the gas. As the bacteria consume all available proteins, the process of decomposition progresses into the next stage: skeletonization.
The term decomposition is a generalized expression covering the overall process from the death of the individual until skeletonization of the body. Putrefaction is only one stage of that process. Material that is subject to putrefaction is called putrescible.
The exact rate of putrefaction is dependent upon many factors, such as weather, exposure and location. Thus, refrigeration at a morgue or funeral home can retard the process, allowing for burial in three days or so following death without embalming. The rate increases dramatically in tropical climates.
The University of Tennessee's Forensic Anthropology Facility is a body farm established in 1981 to study human putrefaction. Several others have been built in other locations since that time.
In alchemy, putrefaction is the same as fermentation, whereby a substance is allowed to rot or decompose, undisturbed. In some cases, the commencement of the process is facilitated with a small sample of the desired material to act as a "seed".