Putrefaction

The first signs of putrefaction are signified by a greenish discoloration on the outside of the skin, on the abdominal wall corresponding to where the large intestine begins, as well as under the surface of the liver.

Certain substances, such as carbolic acid, arsenic, strychnine, and zinc chloride, can be used to delay the process of putrefaction in various ways based on their chemical make up.

As the proteins are continuously broken down to smaller components, the bacteria excrete gases and organic compounds, such as the functional-group amines putrescine (from ornithine) and cadaverine (from lysine), which carry the noxious odor of rotten flesh.

Initially, the gases of putrefaction are constrained within the body cavities, but eventually diffuse through the adjacent tissues, and then into the circulatory system.

As the anaerobic bacteria continue consuming, digesting, and excreting the tissue proteins, the body's decomposition progresses to the stage of skeletonization.

This continued consumption also results in the production of ethanol by the bacteria, which can make it difficult to determine the blood alcohol content (BAC) in autopsies, particularly in bodies recovered from water.

[1] Generally, the term decomposition encompasses the biochemical processes that occur from the physical death of the person (or animal) until the skeletonization of the body.

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 first external sign of putrefaction in a body lying in air is usually a greenish discoloration of the skin over the region of the cecum, which appears in 12–24 hours.

Tight-fitting clothing can delay the process by cutting off blood supply to tissues and eliminating nutrients for bacteria to feed on.

The most common reasons to preserve the body are for viewing purposes at a funeral, for above-ground interment or distant transportation of the deceased, and for medical or religious practices.

Body farms subject donated cadavers to various environmental conditions to study the process of human decomposition.