Abstract
Fifty-six rats were used in the studies here summarized. Before the experiment they had been kept on a stock diet of Purina Fox Chow, Miller's Puppy Meal, and oats fed daily, with the addition of meat, cheese, and cabbage once or twice a week. Litter mates of the same sex, and as nearly the same weight as possible, were selected. The animals were divided into 2 age groups, one varying from 25 to 55 days and the other from 91 to 148 days.
The controls, including half the rats in each age group, received diet No. 1, consisting of starch 64%, casein 18%, butter 10%, salts 3% (Osborne and Mendel's mixture as prepared by Harris Laboratories) and yeast 5% (Fleischmann's bakers' yeast, fresh). The yeast is at least 70% water, and the amount given is evidently inadequate for vitamin B requirement, since we have found that rats kept on this diet invariably die within a few weeks. The animals thrive on the diet if it is modified by trebling the yeast content. Diet No. 2, given to the remaining animals, was similar to No. 1 except that the salt mixture was entirely omitted and replaced by additional starch. The rats of both series received food and tap water in excess of the amount consumed.
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