In an earlier paper (1) we discussed the anion-cation concentration of normal hepatic bile when subjected to the activity of the dog's normal gallbladder. Under these conditions the chloride and bicarbonate concentrations and the pH of hepatic bile decrease, while the base, bile salt and calcium concentrations increase. In every instance fluid is absorbed. In a very limited number of observations we have found the depression of the freezing point of hepatic and gallbladder bile approximately the same, although the total anion-cation concentration was increased considerably in the latter.As a prelude to the anion-cation studies we had studied the effect of gallbladder activity on certain of the individual constituents of hepatic bile when placed in the normal bile-free gallbladder of the unanaesthetized dog (2) (3) (4). It was observed that when the gallbladder became infected the activity of the membrane on the constituents studied was altered considerably. In such instances, water was only slowly absorbed; or, in the more severely damaged organ, fluid actually poured into its lumen, the latter action being a complete reversal of the normal mechanism. Under these circumstances chloride and bicarbonate entered the gallbladder lumen with the inflowing fluid, the chloride concentration of the secreted fluid being about plasma level while the total CO2 concentration was often several times the normal plasma level. Calcium, introduced as calcium lactate, was precipitated, partly in the gallbladder lumen, and partly in the gallbladder wall. Cholesterol in either a colloidal suspension, or in hepatic bile, increased in concentration, but not in total amount when placed in the normal gallbladder. The same was true of bile pigment. When, however, the gallbladder was infected the total amount of cholesterol increased, while the total amount of bile pigment decreased (5).These isolated observations made at a time when we were chiefly concerned with normal function convinced us that a study of the anioncation changes in hepatic bile subjected to the activity of an abnormal 1 Harriet M. Frazier Fellow in Research Surgery. 67