On the Behavior of the Transfused Cellular Elements of Bone Marrow in X-Irradiated Guinea-Pigs

1. A saline suspension of bone marrow from femur, tibia and humerus of 2 to 7 adult guinea-pigs was injected intravenously into another adult guinea-pig that had been irradiated with a lethal dose of X-rays on the whole body (550r). In order to clarify the pattern of the initial distribution of the injected cells, the bone marrow elements to be transfused were labelled with radioactive phosphorus(P32) by injecting it into the donor guinea-pigs 48 hours previously. 2. The amounts of radioactivity recovered per gram of fresh tissue and per organ indicated that chief accumulation of the transfused marrow cells occurred in the spleen and bone marrow. 3. On the 5th day after the marrow cell transfusion, active proliferation of myeloid cells, erythroblasts in particular, began to take place in the spleen. This was accompanied by a slight degree of regeneration of bone marrow. By the 10th day, the activity of myelopoiesis in the spleen was greatly intensified and extensive regeneration of bone marrow was observed. In control animals irradiated with X-rays without marrow cell transfusion, on the other hand, there was no indication of hematopoietic recovery either in spleen or in the bone marrow until the 10th day