Blood-flow relation between hepatic artery and portal vein

Blood flows in the hepatic artery and portal vein have been measured with a square-wave, electromagnetic flow meter. Hepatic arterial flow increased when portal venous flow was decreased, but, when hepatic arterial flow was decreased, portal venous flow also decreased. The relation between the two blood systems can be explained as the simple mechanical effect of interposing a slower-flowing stream in the path of a faster-flowing stream.