The author obtained the following results by the injection of serum and organ extracts of hypoplastic anemia to rabbits. 1) By the injection of serum, the red blood cell count decreased 14% to 35%, Hb 6% to 35%, on the other hand reticulocytes increased remarkably. In the examination of the function of R. E. S., the author observed that there was no change after one time's injection, but slightly after repeated injection of 8 time’s. 2) By the injection of organ extracts (2cc per kg) In the case of the injection of bone marrow extracts, the red blood cell count decreased 25%, Hb, 13%, by the injection of the spleen extracts, the red blood cells 20%, Hb 16%, by the injection of the liver extracts, the red cells 14%, Hb 8% respectively. 3) By the injection of serum or organ extracts, the quantity of sernm iron decreased in the biginning (within a few days), then, gradually increased with an advancing anemia. A rise of P(11) and P(111) fraction of depot iron, especially the latter, in the bone marrow indicated the existence of anemia producing substance which disturbed the hematopoietic function in bone marrow, in the serum and organs of patients with hypoplastic anemia as stated in previous parts Ⅰ and Ⅱ.