Boyden's1 observation that a meal of egg-yolk and cream caused the gallbladder of the cat to empty has formed the basis for the most important of the recent advances made in the study of the physiology of the biliary tract. Boyden's observation has been corroborated by several investigators using many species of animals. It has also been shown that the evacuation of the contents of the gallbladder is due to the contraction of its intrinsic musculature. A complete review of the recent data with regard to the emptying of the gallbladder has been presented by Whitaker.2 The mechanism involved in causing the gallbladder to contract and the reason why fat should be so potent in this respect have not been determined; nor is the relation of the sphincteric mechanism of the common bile duct to the emptying of the gallbladder definitely established. Work on the latter problem was