264 



Dr. J. Joly. 



moderate light stirrmli is parallel with the stimulation of growth by feeble X- 

 or 7-radiation. The photographic reversal by greatly increased illumination 

 compares with the inhibition of growth by the heavy doses of 7-radiation now 

 employed in the treatment of cancer. 



The analogy when further pursued must take account of intrinsic differences 

 prevailing in the two cases. In the living cell there are continuous molecular 

 movements and chemical interchanges accompanied by and attending the 

 ionisation. The static conditions reached in the latent image can only prevail 

 for a brief period which terminates when the ions and electrons find fresh 

 combinations. The image-forming and reversing activities of the plate 

 become respectively represented in the cell by the following events : — 

 (a) Increased liberation of electrons (/3-rays) and attendant formation of ions 

 under the 7- or X-rays. This increases the metabolism, and, in the case of 

 morbid growths, promotes the evil it is intended to cure. (6) With increasing 

 radiation sudden and excessive electrostatic stress (or over-ionisation) brings 

 about immediate reversion to the original molecular state so that molecular 

 changes and reactions are stopped and metabolism ceases. The maintenance 

 of this condition may lead to complete modification of the cell and ultimately 

 to its absorption by the more stable normal cells which are not so readily 

 influenced by the radiation. An alternative view, less in line with the photo- 

 graphic analogy, is to suppose that, with increased density of electronic 

 radiation emanating from all parts of the tissues, an ion freshly formed in the 

 metabolic substance of the cell is almost instantly neutralised by a /3-ray, so 

 that the time required for the molecular movements attending metabolism is 

 not given and growth ceases. 



In another particular we find the cell behaving in a similar manner to the 

 photo-sensitive plate. Physicians ascribe the origin of malignant growth in 

 certain cases to continued local irritation. Here we have a parallel with the 

 photographic plate ; for the latent image, i.e. the ionisation and electronisation 

 of the film, may be obtained by various mechanical stimuli, such as pressure, 

 friction, etc. The inhibition of the growth so produced in the tissues by 

 7-rays compares with the reversal of the pressure or friction marks of the 

 film by light shock. 



The selective action exhibited by the morbid cell towards the radiation, so 

 that these cells are soonest affected by the rays, is significant. The thera- 

 peutic value of the rays depends on this action. To what may it be due ? 



Let us suppose the morbid cell characterised by less stable molecular 

 systems than occur in the normal cell. In other words that the conditions 

 obtaining in it are abnormally favourable to ionisation like a highly " ripened " 

 photo-sensitive emulsion. A feeble radiation will accelerate the activity of 



