1904.] On the Action of Radium on Micro-organisms. 377 



In the case of these micro-organisms, growth was removed from solid 

 media and was exposed to the radium emanations as a film in the 

 depression of a hollow-ground slide, the radium being applied as in 

 the case of vaccine. The vitality of these micro-organisms was tested 

 both before and after exposure to radium by cultivations on media by 

 a similar method to that used in the case of vaccine. 



In some instances metal rings were placed round colonies of bacteria 

 in situ on the surface of nutrient medium, and exposure of bacteria 

 under these conditions made by placing the capsule containing the 

 radium on the rings. 



In the case of each experiment with vaccine and with micro- 

 organisms in pure culture, a control was carried out by making a 

 similar preparation and subjecting it to similar conditions as the 

 experimental preparation with the exception of exposure to radium ; 

 it was also subjected to tests for vitality similar to those used for the 

 experimental preparation, at corresponding intervals of time. All 

 experiments and their controls were made at room temperature. 



The exposure of micro-organisms in liquid media to radium was 

 found unsatisfactory owing to the presence of material of a complex 

 nature between the radium and the micro-organisms, and owing also 

 to the constant variation in the distance between the radium and the 

 micro-organisms suspended in the liquid. 



It was found from the foregoing experiments and their controls that 

 a marked germicidal action was exerted on the specific and extraneous 

 micro-organisms of vaccine and on the other above-mentioned micro- 

 organisms as a result of their exposure to the radium at a distance of 

 1 — 2 mm, for varying lengths of time. 



The following is a summary of the results of these experiments and 

 their controls : — 



Results of Experiments with Vaccine. 



The specific germ in no case survived a longer exposure to radium 

 than 22 hours, at the end of which time it had completely lost its 

 ability to cause vesiculation or any visible irritation at the site of 

 inoculation on a calf. In seventeen out of a total of twenty-five 

 experiments its potency was destroyed after 10 hours' exposure to 

 radium and in four cases after 2 hours. The controls remained fully 

 potent after the experimental vaccines had been rendered inert. 



The extraneous micro-organisms of these vaccines, as has been 

 previously mentioned, consisted of S. pyogenes aureus, S. pyogenes albus, 

 S. cereus flavus, S. cereus albus. In each experiment these bacteria were 

 destroyed after exposure to radium in rather less time than was the 

 potency of the specific germ. In no case did they survive a longer 

 exposure to radium than 15 hours. 



The extraneous micro-organisms of the control vaccines were alive 



