Using the culcure on a cover slip. I have studied the direct influences of ACTH and cortisone upon the bone marrow obtained from patients with blood diseases. The results are as follows: (1) ACTH shows an excellent effect on the bone marrow of intramedullary blood cell arresting type of hypoplastie anemia but no effect on the other types, especially on panmyelophthisis. (2) For the bone marrow of acute myelogenous leukemia, ACTH and cortisone have a good effect but not for the chronic type. Cortisone has a considerably good effect on monocytic leukemia and lymphocytic leukemia. (3) Cortisone is excellently effective for the bone marrow of Banti's disease. (4) ACTH shows an excellent effect on the bone marrow of agranulocytosis and cortisone shows a good effect.