Further Observations on the "Animal Protein Factor"

Summary and Addendum1. Fermentation products of Streptomyces aureofaciens were found to promote growth in depleted chicks on various diets which were adequately supplied with vitamin B12.2. Growth responses in chicks on a corn-soybean diet were also produced by crystalline aureomycin hydrochloride and by cultures in which the aureomycin, as measured by antibiotic potency, was destroyed by alkaline hydrolysis.3. Responses were also obtained with succinylsulfathiazole, streptomycin and 3-nitro-4-hydroxyphenylarsonic acid, but these substances appeared less potent than aureomycin. No responses were obtained with dried whey or dried brewer's yeast.Following the submission of this manuscript, Dr. Paul Gyorgy kindly showed us a manuscript (Gyorgy, P., Stokes, J., Jr., Smith, W. H., and Goldblatt, H., Transactions of Conference on Biological Antioxidants, sponsored by the Macy Foundation, November, 1949) which described a beneficial exerted by aureomycin on growth and the prevention of dietary hepatic necrosis in rats. The assumption was made that aureomycin might act through the suppression of the intestinal flora.The assistance of Vincent Stryeski, Alfred Plattner and Joseph Lang in the care of the animals is gratefully acknowledged.