Rabbits with splenectomy, liver disturbance, reticuloendotherial blocking and the section of the splanchnic nerve were irradiated with ultra-short waves on the Diencephalon for 3 minutes and the behavior of the blood flow and the mobilization of blood cells in the bone marrow were observed. The following are the results. 1) The acceleration of blood flow and the mobilization of blood cells in the bone marrow caused by 3 minutes' irradiation showed no difference between the normal rabbits and the rabbits with such procedures as splenectomy, liver disturvance or the section both of the splanchnic nerve in liver and in spleen branch and the lesser splanchnic nerve in suprarenal branch. 2) In the rabbits with reticuloendotherial blocking by carbon particles, blood flow in the bone marrow was likewise accelerated but the mobilization of blood cells in the bone marrow was not enhanced.