Small areas of the skin in the groin of mice were subjected to an erythema dose of x-rays and a week later a cancer graft was inoculated intracutaneously into the area and at the same time a like graft was inoculated in the same manner in the opposite groin protected from x-rays. The graft in the x-rayed area showed a low percentage of takes, while that in the normal skin gave the usual high percentage When the graft was introduced into the subcutaneous tissues it grew equally as well in the x-rayed area as in the protected area.
Histological examination shows the skin layers, a few days after x-ray treatment, to be markedly infiltrated with round cells of the lymphoid type. The reaction did not extend deeper than the skin layers. It is suggested that this local lymphoid reaction induced by the x-rays controls the graft made into the skin, while its absence in deeper tissues accounts for the growth of the grafts more deeply implanted.