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SCIENCE 



[N. S. Vol. XLII. No. 1079 



method which has now an established place 

 in therapeutics, in the treatment of skin 

 diseases, warts, tumors, cancers, etc. An 

 imposing list of literature from the clinical 

 standpoint bears witness to the practical 

 importance of radioactivity, and many 

 contributions show the interest of medical 

 men. Now all physicians must be familiar 

 with the results of work in this line, and, in 

 addition, every city boasts its experts and 

 specialists in radiography and radiotherapy. 



Thus far, however, clinicians have been 

 chiefly concerned with the formulation of 

 effective methods of treatment, and it has 

 been left for the biologists rather than the 

 physicians to analyze the effects of radio- 

 activity upon living matter. 



The attack on the problem of the effect of 

 radioactivity on tissues and organisms and 

 the use of radioactivity as an experimental 

 means of studying questions of more funda- 

 mental biological importance was at first 

 insignificant. Even yet our knowledge of 

 the effects is very meager; and to our igno- 

 rance of the deeper-ljdng basic principles 

 which govern the action of radium and of 

 X-rays is due the uncertainty with which 

 the extension of the methods to new fields 

 and new problems is viewed by many med- 

 ical men. The analysis of the effects has 

 been taken up only recently and progress 

 in the investigation has not been rapid, with 

 the result that very little constructive worlc 

 has been done. 



In studying the effects of radioactivity, 

 both radium and X-rays have been used as 

 a means of experiment, and the literature of 

 both may be considered together on the 

 basis of the current working hypothesis 

 that the effects of both are comparable, 

 especially in the case of the gamma rays of 

 radium. Radium rays are of three kinds, 

 alpha, beta and gamma ; of these the gamma 

 rays are the most penetrating, and to them 

 are probably due most of the effects on 



living forms. Prom comparative studies of 

 the physicists it is well known that the 

 gamma rays of radium are quite similar in 

 many particulars to the X-rays, and it is 

 stated by Rutherford that they are, in fact, 

 the more penetrating X-rays. Some recent 

 experiments seemed to indicate that the 

 effect of the other rays is by no means 

 negligible, for with the preparation used, 

 when the rays were deflected by a magnet 

 the effect of the beta rays was stronger 

 than that of either of the others. Even in 

 this case, however, the effects seem to differ 

 in degree rather than in the kind of their 

 action, and the results are not in conflict 

 with the hypothesis which is now serving 

 as a working basis for experiment. 



In general, it may be said that when liv- 

 ing cells are exposed to action of radio- 

 activity, the vital functions are retarded or 

 depressed and a permanent injury may 

 result; this depends on three factors, the 

 strength of the radiating substance, the 

 duration of the exposure, and the distance 

 of the object from the source of the radia- 

 tion. When the intensity of the radiation 

 is great, owing to exposure at short range to 

 a strong preparation (or strong current in 

 the case of X-rays) for a long time, the 

 effects are much more injurious than when 

 the intensity is less. Indeed, numerous 

 cases have been reported where a qualita- 

 tive difference results from a slight radia- 

 tion as contrasted with one of great inten- 

 sity, for frequently stimuli which will re- 

 tard growth if of high degree, will be found 

 to accelerate it if weak enough. Exposure 

 to rays of great intensity has been shown 

 to retard or stop growth, differentiation and 

 regeneration, and to interfere with the 

 processes of cell division, sometimes caus- 

 ing degenerative changes to take place in the 

 nuclei, and in one case at least to induce 

 amitosis where indirect cell division had 

 normally been the method of multiplication. 



