The Effect of Radiation

I . INTRODUCTION SINCE the discovery of the x-ray by Roentgen, medical science has evinced great interest in elucidating its mode of action. Today, the problem is by no means completely solved. Certain facts, pirticularly those relating to the results obtained when tissues are subjected to direct radiation, are well established and widely accepted. For example, the aplasia of bone marrow resulting from direct widespread radiation in large doses must be regarded as beyond dispute. However, there are other observations both of a clinical and experimental nature which are poorly understood and highly controversial. These relate particularly to changes in tissues far removed from the direct site of radiation and have led to the postulation of an ‘ ‘indirect’ ‘ action of x-rays. For example, many roentgenologists have privately observed, and others have publicly reported, marked involution of lymph nodes involved in a lymphomatous or metastatic process when radiation was given to other areas sufficiently remote as to have precluded any direct exposure of the former. Equally well known is the marked reduction in the blood count of leukemias treated by x-ray and the leukopenia which develops infrequently in similarly treated nonleukemic individuals, even when supposedly very small areas of marrow are subjected to the effects of direct radiation. These effects, at least in superficial appearance, are not unlike those well established for direct radiation. The result has been a welter of interesting but confusing literature which will presently be reviewed. It is with this possibility of an ‘indirect’ ‘ action of roentgen radiation that this report is concerned. The concept of ‘ ‘indirect’ ‘ action requires further definition. It is inconceivable in an organism whose every cell is bathed in a continuous, circulating fluid medium, and which is interlaced with an intricate network of nervous tissue, that such an agent as x-ray, known to be capable of creating extensive destruction of certain cells, should be without an indirect effect. It is well established that there are indirect’ ‘ effects from a thermal burn or mechanical crush. Yet in the case of crush injuries, at least, the only action directly attributable to the causative agent ceases at the time the trauma is discontinued. What occurs in the organism after that must be regarded as strictly nonspecific, even though these events may be of a highly serious nature at times. We, therefore,