Autografts from spontaneous cancers of mice when replanted into areas previously exposed to an erythema dose of x-rays, failed to grow in the majority of instances (71.4 per cent), while similar grafts inoculated into untreated areas grew in a large proportion of the animals (83.6 per cent).

Autografts of spontaneous cancer, established and growing in the skin, disappeared in 76 per cent of animals after the tumor and surrounding tissues had been exposed to an erythema dose of x-rays, whereas other autografts of similar derivation that had been given a like dose of x-rays outside of the body and had been implanted in the same animals grew progressively in 96 per cent of instances. That this result was not due to a greater susceptibility of the cancer cells x-rayed in situ was shown by the fact that tumors treated in situ with x-rays and then replanted in an unrayed location on the same animal grew actively. Evidently the ray had done no direct damage to the cancer cells.

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