RESULTS

MATERIALS AND METHODS White Wistar rats (Carworth Farms) of both sexes, weighing from 140 to 180 gm., were used. In the first experiment, 80 animals were divided into three groups of ten each, five of each sex. One group was fed a basal 16 per cent casein diet alone, modeled after that used by Popper et al.(34) and composed of: casein (vitamin-free, General Biochemicals), 16 per cent; corn oil, 5 per cent; sucrose, 75 per cent; USP XIII# 2 salt mixture, 4 per cent; with the following vitamins/kg diet: thiamine HC1, 10 mg.; riboflavin, 3.75 rag.; pyridoxine HC1, 10 rag.; nicotinic acid, 37.5.; Ca pantothenate,~ 6 mg.;~ methyl-4-naphthoquinone, 5 mg.; folic acid, 1 mg.; vitamin Bm 0.1 rag.; biotin, 0.~ mg.; choline chloride, 0.8 gm., and oleum percomorphum, 1 ml. The second group was fed the basal ration containing 0.~ 5 per cent DL-ethionine (California Research Foundation) in place of a corresponding