This experiment is directed to study the chronic radiation injury of nail. The ridging of nail plate in chronic radiation damage of nail may be caused by the combination of radiation injury to the nail matrix, hyponychium and nail lamellae. Fragility may be resulted from frequent interruption of mitosis in nail matrix. The thickenning of nail plate was not remarkably observed in this experiment. The thickenning of nail plate reported in man associated with chronic radiation damage to nail can be explained by slowing clown of forward movement of nail plate, incompleteness of successive cell differentiation and coarseness of nail plate. In other words, various changes of nail reported as a chronic radiation injury of nail in man2-4) seem to be ones in the fractionated irradiation in the experimental animal
