The exact mechanism involved in the metabolism of the blood pigments, and the precise relation of the liver to these processes, are still but imperfectly understood. Certain theories, however, concerning blood pigment metabolism are very generally accepted. The pigments of the bile have long been believed to be derivatives, in part at least, of hemoglobin. The work of Eppinger and Charnas,1 Wilbur and Addis,2 Robertson,3 Schneider,4 Hansmann and Howard,5 Giffin, Sanford and Szlapka,6 and others has shown that excessive degrees of red cell destruction are accompanied by an increased elimination of bile pigments. Most observers agree that the liver is the main agent concerned in these metabolic changes. However, the lower bile pigments, principally urobilin and urobilinogen, have been supposed to be formed independently of the liver, by the action of bacteria in the lower intestine, on the bilirubin of the bile. The recent work of Hooper and Whipple7 on