THE AMOUNT of blood flowing through the liver may be estimated using the principle of Fick. If sulfobromophthalein is infused at a constant rate in such amount as to keep the blood level constant, the rate of removal of this dye by the liver is assumed to be equal to the infusion rate. The concentration of sulfobromophthalein in the peripheral blood less the concentration in hepatic venous blood simultaneously withdrawn represents the amount of the dye withdrawn by the liver from each unit volume of the blood. The total amount of blood passing through the liver is calculated as the volume necessary for the removal of the amount of sulfobromophthalein being continuously injected. Bradley and his associates1 have used this method for the study of hepatic blood flow in man. In their studies the samples of hepatic blood were removed through a catheter guided from a vein of the