Gardikas, Kench and Wilkinson1 have found that treatment of human erythrocytes with acetic acid in an oxygen-free atmosphere, in the absence of ascorbic acid, did not yield any biliverdin when the ether solution was extracted with 5 per cent hydrochloric acid. They claim that the bile pigments isolated by Lemberg and co-workers2,3 from human and sheep erythrocytes, and from horse oxyhaemoglobin, may have arisen as an artefact from choleglobin, the latter being formed from oxyhaemoglobin by the action of ascorbic acid ; ascorbic acid had been added in these experiments to prevent the oxidation of biliverdin to bilipurpurin. They have overlooked, however, that bile pigments had been obtained in an even somewhat higher yield without the addition of ascorbic acid, and also from horse carboxyhaemoglobin2. The yield is also unaltered if ascorbic acid is added together with the acetic acid, instead of being added immediately before acidification.