The purpose of this paper is to discuss the significance of cholangiograms obtained during operation which, in association with other circumstantial facts, prove the existence of a physiologic sphincter of the hepatic duct above the point of junction with the cystic duct. PHYSIOLOGIC SPHINCTER Contraction of the hepatic duct may be constantly observed cholangiographically during an operation. It takes place immediately above the crossing of the hepatic and cystic ducts and can be clearly seen when the walls of the ducts are elastic and thin. Neither total nor partial contraction is observable when the excretory passages are either dilated or thickened. In order to prevent artificial dilation of the biliary tract and any possible spasmodic reaction at the level of Oddi's sphincter, iodized poppyseed oil is injected at the rate of 1 cc. a minute to a total dose of 3 cc. in three minutes. Contraction is observable only when