For several years, it has been known that extracts from the liver have a depressor action when injected intravenously. Vincent and Sheen1 showed this in 1903. They also demonstrated that the presence of choline in the extracts was insufficient to explain the effects obtained after intravenous injection, since in atropinized cats a marked depressor action was still obtained. It was not until the publication of the work of Best, Dale, Dudley and Thorpe2 that the vasodepressor action of liver extracts could be definitely attributed to histamine and choline. These workers obtained histamine and choline as pure salts and chemically identified and physiologically assayed them.
Ever since operation was first resorted to for the relief of obstruction of the common bile duct, a certain percentage of the patients have died from a vasomotor collapse occurring some hours after the operation. Clinically, this condition has been known as "liver shock."