1. Historical. The chemistry of the bile acids and their relationship to some other steroids is briefly reviewed. The nature of conjugation, the biological splitting of conjugated bile acids, and the action of bacteria on bile acids is discussed. The physiological importance of bile salts is briefly indicated, and it is suggested that the distribution of the different bile acids in the various animal species has an evolutionary significance. Animal experiments on bile acid metabolism and the effects of oral and intravenous administration of bile salts in animals and man are described. An account of the analytical methods which have been used in the determination of bile salts in body fluids is given.2. Experimental. The colour reaction used here in the estimation of bile salts is described in detail, with recovery of added cholates from blood and the accuracy to be expected. Blood cholate levels in subjects without liver disease, show little diurnal variation, but some alteration over a period of months. Significant differences are found both between the blood cholate levels in subjects with and without liver disease, and in different types of jaundice. There is, however, considerable scatter, so that the estimation is of little diagnostic value. The intravenous cholic acid tolerance test of liver function is compared with other liver function tests, the general biochemical findings, and the histological appearance of the liver. The results of the test in normal subjects, and in obstructive jaundice, active and latent cirrhosis, acute hepatitis, secondary malignant liver disease, and haemolytic jaundice are discussed. The intravenous cholic acid tolerance test has proved insensitive as a liver function test and unsuitable for routine clinical use, but interesting information about the metabolism of bile salts in liver disease has been obtained.<p
