Cardiac output, blood pressure, and organ fractions of cardiac output, except the brain, were determined in rats subjected to tourniquet shock and to hemorrhage. Bleeding involved the withdrawal of 23 and 32 ml./Kg. blood, respectively, and determinations were carried out 5 to 20 minutes after bleeding. Sapirstein's "indicator fractionation" method with Rb 86 was used for the determination of the cardiac output fractions. Blood flow and circulatory resistance of the organs were calculated from the experimental data. Cardiac output was not measured after severe (32 ml./Kg.) hemorrhage. In tourniquet shock at 50 mm. Hg blood pressure, the cardiac output and the blood flow in all organs decrease while vascular resistance of the skin and of the "carcass" (skeleton, muscles, endocrine organs) increases. The heart, "lung," and the liver fractions of cardiac output increase, renal and skin fractions decrease. After moderate hemorrhage at 47 mm. Hg blood pressure, cardiac output and the blood flow of the organs are low. Vascular resistance of all organs other than the heart and the "lung" rises. Cardiac output fractions of the heart, "lung," and "carcass" increase; renal and cutaneous fractions decrease. In severe hemorrhage, the redistribution of cardiac output has a similar tendency but is usually more pronounced.

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