1) The author has experienced 25 cases of so-called Banti's diseases and investigated statistically those clinical picture. 2) The author recognized the marked decrease of hemoglobin and erythroeytes of rabbit by injecting patients serum or spleen extracts one times in one groups and 7 times continuously in another groups. 3) The factor that causes the anemia could not be found in the patients serum on the 30th days after the splenectomy. 4) On the intramedullar circulation test of rabbit bone marrow through the V. nutricia femoris using the serum or spleen extracts, I certified the inhibiting action of the delivery of red blood cells, namely the detaining action of bone marrow (Knochenmakssperre). 5) By investigating myelogram of those patients and that of rabbit after the injection of patients serum or spleen extracts, I recognized the increase of basophilic and polychromatic erythroblasts. According to these facts, I presumed that there must be disturbance for synthesizing hemoglobin. 6) Those above mentioned can be understood according to the remarkable decrease of patients serum-iron and large consumption of iron on the iron tolerance test. The splenogenous toxic factor acts inhibiting and directly on bone marrow but on the iron metabolism.