488 JOHN W. G O W E N 



the observed results different from those expected from direct X-ray 

 absorption. Careful purification may sometimes avoid these diffi- 

 culties or at least trace them do\Mi to substances in the solution ir- 

 radiated other than those of the biological material under investigation. 

 It was pointed out earlier that one of the important effects of 

 radiation is that of altering the inheritance substances, the genes. 

 These changes occur at low doses and are impossible to detect micro- 

 scopically when cells are viewed as the}^ are irradiated. It is well to 

 have these facts in mind when interpreting microscopic investigations, 

 for the microscopic symptoms of irradiation effects may be secondary, 

 induced by the genes and their changed chemical reactions within 

 the cells rather than as a direct effect of the X rays. The effect of 

 the gathering of fat droplets, the denaturization of the protein, etc. 

 may be a secondary reaction instead of the sought-for primary effect 

 of the radiation. 



The particulate nature of the irradiation effects seems quite clear 

 when one examines the genetic chromosome data. These changes 

 are either visible or not, as the case may be. However, the inter- 

 pretation of just what these changes are and how they are caused is 

 not very clear. As mentioned earlier, it has been known for some 

 time that some disinfectants will give the simple exponential curve 

 for the inactivation of bacteria with an increasing dose of the dis- 

 infectant. This is presumably a chemical process. So, too, is the 

 action of radiant energy in the last analj^sis. The importance of 

 these chemical changes to the observed effects is becoming clearer with 

 the demonstration that certain chemicals may also produce gene 

 changes and chromosome breaks and have these gene changes and 

 breaks follow the exponential trend with increasing dosage of the 

 reacting agent (6). Mustard gas and dibenzanthracene (12) just 

 recently have been shown to produce mutations and to cause chromo- 

 some breaks and deficiencies. The biochemical specificity of these 

 changes makes for even greater interest in the relation of X-ray 

 irradiation to the biological effects and their interpretation. 



References 



GENEEAL 



1 . Clark, G. L., Applied X-Rays, 3rd ed. McGraw-Hill, New York, 1940. 



2. Duggar, B. M., ed.. Biological Effects of Radintion, 1st ed. Vols. I and 



II, McGraw-Hill, New York, 1936. 



