By irradiatied rabbits with ultra-short waves on the diencephalon under various conditions, observations on the blood picture in the femur nutrient vein were carried out and the condition of the blood circulation in the bone marrow were measured. At the same time obtaining histological findings and performing the tissue culture of the bone marrow, the following results were obtained. 1) Following the 3 minutes' irradiation, the blood cells in the bone marrow were mobili zed by the acceleration of blood flow in the bone marrow, and scarecely no change of the hematopoietic functions could be observed. After 24 hours, however, the function rose remarkably as the secondary phenomenon of the acceleration of blood flow. 2) Though in the cases wtih successive irradiations every 3 minutes, the increase of both blood cells in peripheral blood and hematopoietic functions of the bone marrow increased but not to the degree mentioned previously. The intensity of acceleration of blood flow and the mobilization of blood cells in the bone marrow in every irradiation were left in about the same degree as in the previous cases. 3) By 30 minutes' irradiation, the bone marrow blood flow was slackened and the blood cells were stored in the bone marrow revealing histologically the depot of blood cells, but the hematopoietic functions remained unaffected. 4) The effect of hookworm toxin generally appearing was reduced to a slight and only transient depot of blood cells in the bone marrow after three minutes' irradiation in the case receiving the human serum with hookworm anemia into the bone marrow circulation.