Abstract
In a recent report 1 it was shown that survival and growth of young rats on diets containing sodium benzoate were possible only if the diets furnished the nutrient materials necessary for growth and especially a supply of glycine, or of a precursor, adequate for the detoxication of the benzoate and for the formation of new tissue proteins. In connection with these experiments, it was noted that certain toxic benzoate diets were less toxic if the rats were kept in cages resting on shavings rather than in raised cages. 2 This fact suggested that glycine or some other dietary factor was obtained by the rats from the excreta or from the shavings. In these experiments the basal diet was supplemented daily with 150 mg. of dried brewer's yeast. Subsequent work showed that this quantity of yeast did not supply the optimum concentration of the vitamin B complex and also demonstrated that the ingestion of the excreta or shavings furnished the needed vitamins rather than glycine.
In the experiments reported in this paper, the basal diet was supplemented with 300 mg. of yeast. On this diet rats grew as well in raised cages as in cages on shavings. This was true in experiments in which the diet was fed ad libitum and also in experiments in which the food intake was restricted (Chart 1). Apparently on this diet the excreta or shavings furnished no additional necessary nutrient substances.
The effect on survival and growth of adding sodium benzoate to the new basal diet is also shown in Chart 1. The toxic concentration of benzoate in these experiments was 3.5%. The toxic concentration of benzoate in the previous experiments was 3%.
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