302 Sir James Mackenzie Davidson [Feb. 2, 



substance, and it only remained for the medical profession to find out 

 in what cases such action would prove beneficial, and in what manner 

 radium could be best applied. The effect upon the skin appeared 

 to be very similar to that of the ic-rays. At the time of the radium 

 application no sensation is experienced, nor is anything abnormal 

 observed for a varying period afterwards. In this respect the phe- 

 nomenon which, in the case of the ic-rays, has been referred to as the 

 " latent period," is repeated. A certain amount of redness and 

 discomfort — the latter in the form of a feeling of heat or burning — 

 then make their appearance. This is the radium reaction, and its 

 severity depends upon the duration of the primary dose. One 

 essential difference between the .r-rays and radium is that while the 

 quality of the rays from a Crookes tube varies considerably from 

 time to time, the output from the radium is quite constant, and 

 therefore the duration of the application is the important factor in 

 its use. 



Biological Effects. — The biological effects of radium have been 

 closely studied upon a large variety of organisms. Its influence 

 upon plant development has been observed, among others, by Koer- 

 nicke, who found * that the general result of the exposure of seed- 

 lings was to cause retardation and eventually cessation of growth of 

 stem and root. In some cases the growth was resumed after an 

 interval ; in others, the plants never recovered. The first effect of 

 the radium rays on dry bean and turnip seeds was to accelerate 

 germination, but after a time the beans ceased to develop, although 

 the turnips showed no signs of arrest — doubtless they would have 

 done so had the exposure been prolonged. A tube of radium placed 

 on a leaf will cause the irradiated area to lose its chlorophyll and to 

 assume autumn tints. 



Micro-Organisms. — ^A considerable amount of research has been 

 carried out upon micro-organisms. Anthrax microbes have been 

 found not to develop at all if left for 24 hours in an atmosphere 

 charged with radium emanations. In Metchnikoff"'s laboratory at 

 the Pasteur Institute recently f it has been proved that certain toxins 

 tend to lose their virulence after being made radiferous. When 

 diphtheritic toxin was left for thirty days in contact with minute 

 quantities of radium sulphate, the poisonous effect of the toxin was 

 found to be much less rapid than in the case of the same toxin 

 which had not been treated in this fashion. An interesting exception 

 was noted in the tetanus toxin, upon which radium seemed to have 

 no retarding influence. 



The virus of rabies has been speedily destroyed when exposed 

 directly to radium emanation, and Phisalix % has demonstrated the 



* Himmel und Herde, Oct. 1904. 



t Archives d'dlectricitc mddicale, Sept. 25th, 1911. 



X Academy of Sciences, Paris, February 22nd, 1903. 



