Dixon & Wigham — Radiations from Radium Bromide. 185 



In considering which of the radiations emitted by the radium 

 bromide were responsible for the inhibitory effects observed in 

 these experiments, it is evident that we may leave out of account 

 the a radiations. It has been shown that they are stopped by the 

 glass of the containing tube, and consequently do not act on 

 either the organisms or on the matter. Neither is the feeble 

 phosphorescent light emitted by the radium bromide responsible 

 for the inhibition ; for we found that the radiations from the 

 tube were effective in arresting growth after passing through a 

 screen of platinum foil 0'04 mm. thick. 



It follows that in our experiments it must have been the /3 or 

 Y radiations, or both, which produced the effects observed. It 

 does not seem probable that the y radiations by themselves were 

 very effective, since, being very penetrating, they can scarcely 

 be supposed to have been absorbed by a thickness of 30 mm. of 

 air ; beyond this distance from the radium, the radiations were 

 apparently ineffective. 



Physicists have shown that the /3 radiations are electric charges 

 of negative sign moving at an immense velocity. It appears 

 undecided whether they are associated with matter or not. If 

 they are, the mass of each corpuscle carrying the negative charge 

 cannot be greater than the one-thousandth part of an atom of 

 hydrogen. The charge carried by the electrons, or corpuscles, as 

 they are called, is equal to the available charge on a monad ion. 

 The y radiations are not themselves negative electrons, but may 

 cause bodies exposed to them to give off electrons. 



In our experiments the negative electrons emitted directly 

 from, or produced indirectly by, the radium bromide were in part 

 absorbed by the bacterial cultures. In this process it seems 

 natural to assume that they attach themselves to the positive ions 

 of the cultures, and amongst others to the H' of the water within 

 the bacteria. In this way OH' ions would be set free. In other 

 words, the water in the protoplasm would become alkaline. The 

 alkalinity would check the action of the enzymes, on which the 

 metabolism of the cells depends ; for it is known that the action of 

 all enzymes, with the exception of trypsin, is inhibited in an alka- 

 line solution. This working hypothesis seems to fall in with the 

 observations we have been able to make up to the present. While 

 exposed to the vigorous bombardment of the electrons, it would be 



