2. This preparation has been satisfactorily reproducible in this laboratory in more than 90 separate sequential perfusions. Absence of a sensitive hepatic venous smooth musculature contributes to the ability to maintain satisfactory perfusion for as long as 24 hours.

3. The perfusate was usually maintained bacterially free for at least the first 12 hours of perfusion without the use of antibiotics. The perfusate was maintained at normal body temperature and, by varying the CO₂ content of the oxygenating gas, within a physiological pH range. The importance of these features when studying problems of intermediary biochemistry and ultrastructure is emphasized.

4. The liver of the bovine calf is sufficiently large to permit (a) simultaneous and independent perfusion through the hepatic artery and portal vein, and (b) repeated sampling of hepatic tissue without interruption of the circulation.

5. Excellent, viable condition of the isolated liver, throughout many hours of perfusion, was demonstrated by steady state of oxygen consumption, efficient clearance of bromsulphalein dye, continuous secretion of bile, constancy of blood flows and pressures, and very minimal alterations from normal in histologic and ultrastructural detail.