1. The effect of diets, varying in quantity or quality of protein, on hemopoiesis was studied in protein depleted and anemic adult rats.
2. In experiments with diets containing different amounts of casein (0, 3, 9 and 18 per cent, respectively), and fed ad libitum, it was found that with a protein-free diet a further decrease of hemoglobin occurred, whereas the other three diets initiated a regeneration of hemoglobin; its degree being more or less proportional to the casein content.
3. In experiments, in which diets with 9 and 18 per cent of casein, respectively, were given in restricted amounts, it was found that the degree of hemoglobin formation was similar to that with the same diets when given ad libitum, whereas the weight gain was considerably less. It is concluded, therefore, that in caloric deficiency hemoglobin formation has a priority over weight recovery.
4. A diet containing 30 per cent casein and given in restricted amounts induced a further weight loss, whereas the concentration of hemoglobin showed a marked increase. Comparing the results obtained by this diet with those observed with 18 per cent casein diets, given either ad libitum or in controlled amounts, it was evident that restriction of the quantity of food protein interferes more seriously with hemopoiesis than restriction of calories.
5. Diets containing nutritionally inferior proteins fed at 9 per cent level, also impaired normal hemopoiesis. Hemoglobin regeneration induced by the proteins investigated was found to decrease in the following order: eggs, meat, processed soya, casein, peanut, maize, wheat, gelatin.
6. Comparing the nutritive value of various proteins for regeneration of hemoglobin and of granulocytes it was found, that casein and soya and maize proteins are considerably more efficient for hemoglobin formation than for production of granulocytes, whereas wheat protein and gelatin have a higher granulocytopoietic capacity.