Cortisone and Homologous Transplantations of Tumors *

The first evidence of reaction to the graft was a rapid aggregation of polymorphonuclear leucocytes in the surrounding tissues of the host, beginning about two hours after the introduction of the tumor fragment and of short duration only. The leucocytes collected about any necrotic material present and even penetrated between the tumor cells. About fifteen hours after the introduction of the graft there occurred proliferative changes in surrounding areolar connective tissue of the host, the cells of which became shorter and thicker, while their nuclei divided by amitosis. The proliferating cells migrated into the cleft which originally separated the connective tissue of the host from the newly introduced fragment, and applied themselves to the surface of the graft. The stroma had already become hyaline after twenty-four hours, and commencing degeneration could often be detected in its cells. Such changes were even more distinct after thirty-six hours.... The capillaries of the graft with their blood corpuscles were still recognizable, although the endothelium showed degenerative changes. Outside of the graft fibrin filaments had appeared in the exudate and amitotic division of the connective tissue cells was still in progress, while spindle-shaped wandering cells had begun to penetrate the transplanted tumor. Three days after inoculation the cleft between the tumor and the host's tissues was almost obliterated, and wandering cells could be distinguished in the interstices of the graft, where they were dividing by mitosis. Mitotic division was in evidence, also, in the fibroblasts of the host nearest the tumor. . . . No development of new blood vessels had yet occurred and the whole mass of transplanted tissue remained without vascular supply. Four days after transplantation, however, an ingrowth of capillaries had taken place and vascularization was in such rapid progress that all stages of new capillary