The object of this study was to determine the function of the large intestine as an excretory organ and to consider its probable rôle in absorption under normal conditions. The opportunity for such a study was presented by a young woman who had been subjected to a single barrel permanent ileostomy which had left an isolated large intestine. At operation the ileum, which had been severed close to the ileocecal junction, had been brought out through the abdominal wall. Hereditary polyposis of the colon had constituted the indication for this operation, which had been performed as a preliminary measure to colectomy. This procedure permitted the collection of the excreta of the small intestine, and the products of the isolated colon could be recovered at the same time. In this manner it was possible to determine the composition of the intestinal material that normally is delivered to the large intestine and,