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Feces (also spelt faeces) is the excrement from the digestive tract expelled from the anus of animals by defecation. It consists of water, undigested food residues, digestive secretions, and bacteria. The reddish-brown color of human feces is derived from stercobilin, created by bacterial action on bilirubin and subsequent oxidation. Feces are also known as scat and scatology is the study of feces.

Feces are generally a taboo subject (see toilet humour). This is probably because of the need to keep feces well away from food, for health reasons.

Coprophilia is a sexual attraction to feces. Coprophagia is the extremely hazardous practice of eating feces.

Laboratory testing of feces As well as being a chair[?] without a back support, a stool is a term used for a feces sample that requires medical testing.

Faeces will usually be required for microbiological testing, looking for an intestinal pathogen[?].

Biochemical tests done on faeces include faecal elastase[?] and faecal fat[?] measurements, as well as tests for faecal occult blood[?].

It is recommanded that the clinician correlateds the symptoms and submit specimen according to laboratory guidelines to obtain results that is clinically significant. Formed stools often do not give satisfactory results and suggest little of actual pathologic conditions.

Three main types of microbiological tests are commonly done on faeces:

Antibody-antigen type tests, that look for a specific virus (e.g. rotavirus).
Microscopic examination for intestinal parasites and their ova (eggs).
Routine culture.

Routine culture involves streaking the sample onto agar plates containing special additives, such as MacConkey's Agar[?], that will inhibit the growth of Gram positive organisms and will selectively allow enteric pathogens to grow, and incubating them for a period, and observing the bacterial colonies that have grown.

The main pathogens that are commonly looked for in faeces include:

Salmonella and Shigella
Yersinia (this tends to be incubated at 30°C, which is cooler than usual.)
Campylobacter (incubated at 42°C, in a special environment.)
Aeromonas[?]
Candida (if the person is immunosupressed e.g. cancer treatment.)
E. coli O157 (if blood is visible in the stool sample.)