In 1919, Lyon 1 described a relatively simple clinical method for the diagnosis and treatment of diseases of the gallbladder and biliary ducts. This, in brief, consisted in the drainage of the biliary tract through a duodenal tube after relaxation of the sphincter of Oddi by the local application to the duodenum of a concentrated solution of magnesium sulphate. The method was based on a suggestion from Meltzer 2 that magnesium sulphate might relax the sphincter of the common duct and permit the ejection of bile into the duodenum. By making use of this procedure, Lyon believed that he could collect separately bile from the common duct, the gallbladder and the hepatic ducts, and could study each sample chemically, bacteriologically and cytologically. The potential importance of Lyon's work was immediately recognized, and already a large and somewhat conflicting literature on the so-called Meltzer-Lyon test has accumulated. Certain observers, notably Brown,3 Smithies 4 and Sachs,5 confirm Lyon's observations and believe that the method is of great practical value both in diagnosis and in treatment, while others, such as Dunn and Connell,6 Bassler, Luckett and Lutz,7 Cutler and Newton,8 and Hartman,9 are less enthusias¬ tic concerning its efficacy. Despite the varying results that have been reported, two facts with regard to the method remain outstanding : It affords a means for the clinical study of the excretion of the biliary pas¬ sages, and it allows the study of liver function from a fresh point of view.In a recent review of the origin and significance of the constituents of bile, Whipple 10 has pointed out the need for critical analysis of the data obtained by Lyon's method in order to guard against too free interpreta¬ tion of results. With this warning in mind, it has seemed of interest to compare the reported character¬ istics of bile obtained through the duodenal tube by Lyon's method under various conditions with analyses of specimens of bile which were obtained directly from a known source in the biliary tract under known pathologic conditions.For this purpose we have obtained samples of bile from the gallbladders removed at operation in a series of cases of gallbladder disease at the Mayo Clinic. We have noted the color and turbidity of the bile, estimated its specific gravity and viscosity, determined the con¬ centration in cholesterol, nitrogen and urea nitrogen, examined the sediment microscopically, and finally attempted to correlate the results obtained from such analyses with the clinical and operative findings. These constituents of bile were selected for study because most workers with the Meltzer-Lyon test have drawn conclusions of clinical importance from changes in the specific gravity, viscosity and color of the various bile specimens, and have placed considerable emphasis on the bile sediments and cholesterol content. The urea nitrogen and total nitrogen were estimated, with the hope that the findings might reveal information of interest.The material at our disposal consisted of seventy-two ...