IN his address to the Seventh Congress of Biological Chemistry in Liege on October 3–6, 1946, Dr. H. D. Kay summarized some experiments on feeding pigs with yeast, carried out during the War at the National Institute for Research in Dairying in Reading1. It was found that when the total food ration contained 8 percent dried yeast, some of the animals developed stiffness and lameness, and were finally unable to stand. If the diet contained 20 percent yeast, this condition developed rather rapidly in all pigs. X-ray examination of the bones indicated that the pigs were, in fact, suffering from rickets. The rachitic symptoms could be prevented by a sufficient supply of vitamin D, and could be almost completely prevented by increasing the calcium carbonate content of the diet from 1.5 to 4 percent. When the yeast phosphorus was replaced by the corresponding amount of sodium phosphate phosphorus, no symptoms were produced.