The factors which determine the survival of glandular transplants have interested investigators and clinicians for years. It has been generally found that the transplantation of tissue into an individual of the same species—homografting—or into an individual of a different species—heterografting—is unsuccessful, whereas the reimplantation of tissue into the same individual is frequently successful. Transplantation of the latter type, or autografting, is, however, not always successful. To explain the failures, it has been proposed that one of the important factors in determining the survival of autotransplants is the physiologic need of the organism for the tissue in question. Cristiani1 was the first to suggest such a deficiency as a determining factor, for he found that thyroid tissue engrafted into rats survived only after a partial thyroidectomy had been performed. His conclusion does not seem justified, however, since the tissue which was successfully transplanted was an autograft, whereas that which was