Washed chicken red blood cells (CRBC) were injected into the popliteal lymph nodes of the rabbit by way of the efferent lymphaties and the fate of nucleated CRBC in the nodes was studied, together with immune cellular proliferation in the lymphnodes provoked by the injection of CRBC. The chief results obtained are as follows: 1. In normal rabbits that had not been sensitized with CRBC, the injected CRBC underwent hemolysis and their nuclei were found diffusely scattered over the wide area of the popliteal nodes, particularly in the lumen of lymphatic sinuses until 2 hours after the injection 2. At 6 hours after the injection the nuclei of the injected CRBC were mostly phagocytized by the reticular cells in the lumen of lymphatic sinuses or other parts of the nodes. Thereafter, the nuclei of CRBC had been digested nearly complitely by the reticular cells and disappeared by the 12th hours after the injection. 3. In the sensitized rabbits that had been intravenously injected with CRBC two weeks ago, phogocytosis of the injected CRBC by the reticular cells occurred at 2 hours after the injection and CRBC disappeared nearly completely by the 6th hours, after having been digested by the reticular cells. 4. In the sensitized rabbits, the immune cellular responses in the lymph nodes, proliferative reaction of pyroninophilic blast cells and plasmocytes in particular, occurred more
rapidly and to a greater extent than in the normal rabbits that had not been previously injected with CRBC.