1. Jukes, T. H., and Williams, W. L., Pharmacol. Rev., 5, 381 (1953).
2. Elam, Gee and Couch, Proc. Soc. Exp. Biol., N.Y., 8, 832 (1951).
3. Ministry of Agriculture Advisory Leaflet No. 104, Pig Feeding, p. 2 (H.M.S.O., London, 1953).
4. Fell and Stephenson, Poultry Sci., 32, 1092 (1953).