The author studied what influences might be exerted on the iron and copper metabolisms in rabbits by anemia-inducing, substance found in the patient with the so-called Banti's disease, and obtained the following results. 1. In the rabbits injected with the serum or the spleen extract of Banti's disease patients, there can be recognized a decrease in the number of erythrocytes and in the serum iron content and an increase in the serum copper content. 2. After injecting the serum and the spleen extract of the patient to rabbits, the iron and copper contents in the liver and spleen of the animals were measured. From these results as well as from their bone marrow picture, and the serum iron and copper contents it has became clear that the mobilization of the stored iron is disturbed and that the copper metabolism is involved in it. 3. Even in the non-toxic splenomegaly (Tomoda) it has been recognized that there exists an agent that induces changes in the iron and copper metabolisms.