Whole Body Irradiation—Radiobiology or Medicine?

1. Suggested causes of death after single doses of radiation are briefly reviewed. Species differences are prominent. 2. The dose-mortality relation for mammals killed by radiation shows less variability than mammalian responses to other toxic agents. Possible reasons for this are discussed and also its relevance to attempts to find substances which protect in vivo against irradiation. 3. Cell death after whole body irradiation seems to occur in two ways. Delayed death due to interference with cell division is well known, but probably more important in accounting for the immediate histological effects of radiation is some other mechanism responsible for the early death of cells which normally do not divide. 4. General principles of radiobiology are shown to need modification if they are to be applied to whole body irradiation of mammals.