184 Scientific Proceedings, Royal Dublin Society. 



diffusion to take place between the patch and the surrounding 

 culture. Fig. 2, Plate XVIII., is a reproduction of a photograph 

 of a plate obtained in the way just described. The photograph 

 was taken three days after the inoculation of the patch. 



In several of the thicker cultures it was noticed that, while the 

 growth of the culture was inhibited at the surface next to the 

 radium-tube, colonies more deeply embedded in the medium 

 ultimately developed. In order to obtain more precise informa- 

 tion, as to whether this immunity towards the radiations was due 

 to the screening action of the medium, or to the anaerobic condi- 

 tions obtaining in the deeper parts of the cultures, we exposed other 

 cultures to the radiations under completely anaerobic conditions. 



The arrest of growth also takes place in cultures exposed 

 anaerobically. We have found this to be the case with B. anthracis, 

 B. pyocyaneus and B. typhosus. It consequently follows that the 

 inhibition is neither due to the ionisation of the air nor to the 

 production of ozone by the radium. Unfortunately in making this 

 experiment our radium bromide met with a mishap. To fit it 

 conveniently into the hydrogen chamber, it had to be transferred 

 from its tube into a cell, formed by a perforated micro-slip covered 

 above and below by a thin plate of mica sealed on by Canada 

 balsam. For some reason, probably owing to the absorption of 

 the remnants of oxygen in the anaerobic chamber by the alkaline 

 pyrogallol, the pressure inside the little cell burst open its covers, 

 and moisture got in. However, when the culture-plates were 

 examined, after three days' growth in the anaerobic chamber, 

 sterile patches were found in each of the cultures mentioned 

 above. The cultures of B. pyocyaneus and B. typhosus were 

 within 3 mm. of the radium- tube, while the anthrax culture 

 was at a distance of 6 mm. The culture of the B. pyocyaneus and 

 the mica plate which supported it also intervened between the 

 radium-tube and the anthrax. In spite of this, its culture showed 

 perceptible inhibition in its central region. A culture of B. pro- 

 digiosan, also at 6 mm distance, and with the typhoid culture and 

 its mica plate intervening, showed no sterilization effects due to 

 the radiations. It is uncertain in this experiment how long the 

 radiations were allowed to act before the radium salt became 

 moist. 



