Rats fed on a synthetic diet for 17 days declined rapidly during this time and failed to make any appreciable gains in weight when fed, as supplements, moisture-free livers that had been dried at 100° C in air, whereas rats receiving equivalent amounts of raw liver, in connection with the synthetic ration, made rapid gains. Other rats receiving raw potatoes and tomatoes as supplements to the synthetic diet and dry liver, made appreciable gains, whereas rats fed equivalent amounts of cooked potatoes and tomatoes made little or no gains in weight.