186 Scientific Proceedings, Royal Dublin Society. 



impossible for the cells to secure suitable conditions for the 

 efficiency of their enzymes ; whereas, when transferred outside 

 their range, the alkalinity might be neutralized and metabolism 

 recommenced. Where the intensity of the bombardment was 

 feeble, diminution of the activity of the enzymes would ensue, 

 causing retardation of growth, as has been observed on the margin 

 of the sterile patches. 



If, as this speculation demands, there is a production of OH' 

 ions in the media exposed to the action of the radiations coming 

 from the radium-tube, we ought to be able, by the use of indi- 

 cators, to detect their presence. It might be thought that, the 

 mass of the electrons being so hopelessly small, it would be 

 impossible to detect their presence by chemical means. But it 

 must be remembered that, according to theory, each electron 

 is capable of neutralizing a positive ion, and at the same time 

 of setting free a negative one. 



As might be expected, all indicators are not equally suitable 

 for this detection. Thus no indication of the presence of OH' 

 ions could be detected when litmus or methyl orange was 

 exposed to the radiations. This is probably owing to the fact 

 that these indicators are themselves strongly ionized in aqueous 

 solution. With phenolphthalein, which is scarcely ionized at all, 

 the case is different ; and we might expect the colour change when 

 the OH' ions were liberated by the neutralization of the H' ions 

 by the negative electrons. 



With this indicator our expectations appear to have been 

 realized ; and in several instances we have found, after exposure 

 to the radiations for one or two days, the development of a feeble 

 pink colour in an agar medium, through which previously colour- 

 less phenolphthalein was diffused. This is the more satisfactory 

 as the amount of radium bromide available for these experiments 

 was very small, much of the original quantity being lost in the 

 accident before alluded to. The agar in these experiments was 

 spread on mica plates, which were enclosed in a space deprived of 

 C0 2 by the presence of a strong solution of caustic potash. 

 Control experiments on the same plates, in the same chamber, but 

 not exposed to the radium radiations, did not give any coloration. 



We must remember, however, that the coloration may be due 

 to the direct ionization of the indicator, as well as that of the water. 



