In the observations carried on the bone-marrow tissue culture in the following three experimental anemias and the results mentioned below were obtained. 1) Saponin-induced anemia: Histologically bone marrow changes to hyperplastic and the number of marrow-fat cells decrease. In the bone marrow culture the tissue growth is better than that in the control, and the cell function tends to be accelerated. This seems to be caused by the inability to attaine the saponin concentration in blood over a certain limit due to the paucity of its absorption and by changes in the sensitivity of bone marrow to saponin after injection. 2) Phenylhydrazine-induced anemia: Histologically fat cells of bone marrow decrease and disappear, and bone marrow itself uniformly turns hyperplastic, but in tissue culture of such bone marrow the tissue growth is either better or poor, and the cell function is either accelerated or diminished. Consequently, even though histological picture is the same, the bone marrow function is not the same, these indicate that the bone marrow function in stimulated state changes to an inhibited state. 3) Anemia induced by prolonged blood depletion: Fat cells of bone marrow decrease in number and the bone marrow becomes hyperplastic, and in bone-marrow tissue culture the tissue growth is better and the cell function is accelerated. In addition, it seems that the plasm of this anemia containes the factor which stimulates the bone-marrow tissue growth.