Faeces, the excrementitious matters discharged by animals from the lower bowel. The average amount of faeces eliminated by the human adult in the course of twenty-four hours is six or eight ounces. The composition of the faeces is about three parts of water and one part of solids. The latter consist of the more insoluble parts of the food which have resisted the action of the digestive juices (e.g. particles of cartilage, woody tissue, muscular fibre, etc.); of mucus and epithelial scales: of mineral salts; of various substances derived from the bile; and of certain specially named constituents (excretin, stercorin, etc.).