The effect of haemorrhage on hepatic artery and portal vein flows in the anesthetized cat.

1. In cats anaesthetized with pentobarbitone, the hepatic artery and portal vein flows and pressures were recorded simultaneously.2. Removal of blood from the animal did not cause a decrease in the hepatic artery flow unless the arterial pressure fell below 80 mm Hg. In contrast, the portal vein flow fell markedly.3. After restoration of the blood, the hepatic artery flow increased to above the pre-haemorrhage level, while portal vein flow returned only partly towards the control level.4. It is concluded that haemorrhage causes a vasodilation in the hepatic artery vascular bed and a vasoconstriction in the vascular beds drained by the portal vein. By this means, the oxygen supply to the liver is maintained as far as possible.