THE effects on mental processes of the exposure of the human central nervous system to irradiation has not been investigated extensively because of the potentially hazardous and irreversible results on living human tissue. The available information on this subject has had to be extrapolated from experimental laboratory studies on infrahuman animals or gleaned from the accidental exposure of man or from the analysis of the symptoms of the survivors irradiated at Nagasaki and Hiroshima.
More recently it has also been possible to obtain some information on this subject from the performance of patients with advanced neoplastic disease who have been treated with whole body radiation. The latter source of data is the only planned type of investigation of radiation effect on human beings that is feasible at present and, hence, any information available by this means cannot fail to add to our inadequate knowledge