The earlier work on the respiratory metabolism of the blood itself was in large part rendered valueless because of lack of knowledge of the growth of micro-organisms, the effects observed being merely due to bacterial action.1It has been shown, however, by Warburg, and by Morowitz and his pupils, that each of the principal formed elements of the blood, leukocytes, erythrocytes, and platelets, has, under certain circumstances, a measurable oxygen consumption. Studies of the oxidative properties of nucleated and unnucleated erythrocytes were made by Warburg2in 1909. He determined the oxygen capacity of defibrinated blood with the Barcroft-Haldane apparatus, and redetermined the oxygen absorption which had taken place after incubation at body temperature for a period, protected from the air. Normal human blood consumed very little oxygen, the amounts absorbed during short periods of incubation being less than the margin of experimental error, while the changes in blood left for