The coloring of animal tissues with Sudan III was known as early as 1896 by an Italian Scientist, Daddi. Dr. Oscar Riddle of Chicago University was one of the first to continue with color work. It was through the incentive of an address by him before the zoological meeting at Chicago, 1907–8, that the feeding of color dyes was begun at Cornell University. Dr. Gage, Professor of Histology and Embryology, with the Department of Poultry Husbandry in co-operation, started several experiments of feeding Sudan III to hens.2 The work has since been continued by the writer, using other dyes in addition to Sudan III. The Nature and Action of the Dyes Sudan III is a common aniline dye, a compound from Amidoazobenzene and B.—Napthol. It is soluble in alcohol, ether, benzene, petroleum, ether, oils and fats. When fed to fowls it apparently colors the fat deposits only. In . . .