A Theory of the Action of Rays on Growing Cells. 265 



the morbid cell and yet scarcely affect the normal cell, the latter corre- 

 sponding to a " slow " photo-sensitive film. Increased radiation which only 

 attains the point of accelerating interchange in the normal cell may be 

 attended by a sufficiently dense /3-radiation to inhibit the metabolism in the 

 morbid cell in the manner already suggested. In other words — to revert to 

 the analogy with the photo-sensitive salt — the amount of ionic and electronic 

 stimulus which builds the latent image in the " fast " film is insufficient to 

 affect the " slow " film and as the stimulus is increased the latent image of the 

 first suffers reversal at a point which builds up the latent image in the 

 second. This appears to be just what is observed in the case of radiation 

 treatment, the success of the method depending upon a lag in the effects 

 arising in the normal tissues, as compared with those arising in the morbid 

 tissues. 



It may also be urged for the present view that if the effects of 7-rays on 

 the growth of the cell are not of a photo-electric character, and so productive 

 of ionisation, we must recognise in them some quite new reaction between 

 matter and light. This seems a needless course when there does not appear 

 to be any a priori objection to urge against the unification of our views 

 respecting the photo-stimulation of the sensitive salt and the effects of 7-rays 

 on the molecular systems existing in the cell. 



Assuming a real basis for the approximation of the two processes, the 

 question as to how the peculiar constitution of the morbid cell may arise 

 deserves more careful consideration than I am competent to give to it. Upon 

 the photographic analogy we might reason thus : — If, in the life of the cell, 

 ions are naturally always being formed, the absence of a " restrainer " might 

 lead to morbid ionisation ; or, again, the presence of a " sensitiser " — the 

 former to limit the ionising activity either physically by its inert properties, 

 or chemically ; the latter to accelerate it by removing the products of reaction 

 as fast as they are formed. Dr. Lazarus-Barlow, however, has found notable 

 and excessive quantities of radium in certain tumours. If this was general 

 to all spontaneously arising cancers we might find here a sufficient cause of 

 excessive ionisation. In this connection it is perhaps significant that the 

 study of the distribution of cancer has been found to follow in a notable way 

 the nature of the soil constituents of the district. Thus it is stated that 

 cases of cancer are more frequent in clay-covered areas than in calcareous 

 regions. Now calcareous rocks are almost without radioactive constituents, 

 whether of the uranium-radium series or of the thorium series. The amounts 

 of emanation continually being exhaled from such soils must be very different. 

 It would be interesting to directly examine the several districts for soil- 

 emanation. 



