THIS investigation was stimulated by the observation that surgeons differ concerning the advisability of removal of fluid blood and clots from the peritoneal cavity after intraperitoneal hemorrhage or operative procedures. The purpose of the experiments was to determine the fate of blood introduced into the peritoneal cavity, its possible usefulness as a substitute for transfusion on occasions when the usual methods are inapplicable or too difficult and its effect on the blood volume, hematocrit reading and hemoglobin and total protein levels. Additional observations were made to determine if the clinical leukocytosis so frequently observed after intraperitoneal hemorrhage is due to the hemorrhage alone or to the mere presence of blood within the peritoneal cavity. The response of the peritoneum itself to repeated intraperitoneal injections of autogenous blood was also determined. A review of the literature concerning peritoneal absorption prior to 1923 was written by Cunningham.1 The method of administering