Roentgen Radiations in Biological Research

The purpose of this paper is to recount briefly the work of those biologists who first studied the effect of roentgen rays on living cells, and to show how the results that they obtained, often under great difficulties, have provided the basis of subsequent investigation. Progress in this field has not been steady. During the first dozen years after Röntgen's discovery, the pioneers carried on exploratory work and saw dearly the fundamental problems which should be solved. But in the next dozen years interest in x-ray research waned, although radiotherapy was advancing rapidly. Biologists turned their attention to radium radiations and with their use made important contributions, especially to experimental embryology. Early in the third decade of the present century x-rays again began to be used in biological research and have been increasingly employed ever since. The literature is now extensive. In this review it is possible to cite only a few examples of research in some of the fields of investigation. The Early Investigators Those who first tested the biological effect of x-rays on small organisms were interested in determining whether they could be used as a bactericidal agent. Handicapped by the low intensity of the beams produced by the static machines then in use, and by the fact that bacteria are relatively resistant, they were unable to find any effect at all. In 1898, however, Rieder (59) demonstrated that growth could be somewhat inhibited. Biologists then turned their attention to plant cells and to Protozoa, whose reactions could be more easily observed. Lopriore in 1897 (46) noted that the circulation of the protoplasm in the cells of certain water plants was accelerated after a moderate exposure to x-rays and that it returned to a normal rate in a short time. A longer exposure terminated in the coagulation of the protoplasm, an observation confirmed a little later by Schaudinn (63), and more recently by others who have used, also, gamma rays and the ultraviolet. The retarding action of the rays on cell division was noted by Koernicke (40), who observed that, if the exposure was not too severe, normal growth might be resumed; the injured cells were capable of recovery. He also demonstrated that seeds exposed after they had taken up water and had started to germinate were more sensitive than dry seeds. In this connection, the observation of Schaudinn is of interest. He found that there was a wide difference in sensitivity among different kinds of Protozoa, and that those with highly fluid protoplasm were more susceptible than those with less fluid protoplasm. Thus the physiological condition of the cells at the time of exposure was shown to be a factor in determining sensitivity. At this time it began to be suspected that x-rays might be the cause of the sterility developing in clinical radiologists.