I954 reacting 'directly' in the van den Bergh test. Their absorption curves are similar, though not identical, and they differ from that of bilirubin. 3. The visible absorption curves of the azo compounds of these three pigments are indistinguishable. 4. The two direct-reacting pigments of serum occur in small amounts in the urine of patients with obstructive jaundice, and in large quantities in gallbladder bile obtained at necropsy, where they are more abundant than bilirubin. 5. The proportion between the two directreacting pigments of serum is variable. 6. There is evidence that other diazo-positive pigments occur in bile and urine.