Cooked pork kidney is the richest source investigated, of the factor or factors which cure or prevent the dermatitis due to egg white, as it is necessary to include only one-sixth of the weight of the egg white present in a ration, for a cure. Cooked beef liver, pork liver and beef kidney are good sources, being effective if present in the ration in a concentration about onefourth that of the egg white. One to three times the weight of the egg white, of dried yeast, dried egg yolk, wheat embryo or dried milk must be incorporated to be curative. There is relatively little or no potency in spleen, heart, ovary, adrenal, blood or hemoglobin. The activity resides in the solid liver residue left from the preparation of Eli Lilly & Co. liver extract no. 343, not in the extract itself. The potency of liver does not depend on its nucleoprotein fraction. Cooking increases the activity of raw liver or kidney; autolysis or extensive bacterial action does not decrease it. Prolonged heating, i.e., 6 days at 100°C. is destructive, especially if the material is dry. Boiling with hydrochloric acid for 1 hour at 5 or more per cent decreases the potency appreciably. A low hemoglobin concentration is not a feature of the syndrome due to dietary egg white. The injurious action of egg white apparently does not depend on the destruction of some dietary factor within the ration mixture.