278 RADIATION BIOLOGY 



conceived in terms of specific chemical reactions. Support for the chem- 

 ical nature of these changes comes from the radiomimetic effect of sulfur 

 and nitrogen mustards which can cause chromosome breakage as well as 

 mutations. Thus the belief that chemical reactions intervene between 

 the absorption of radiation energy and the final biological effect rests on a 

 firmer experimental basis than hitherto. 



How far it is possible to make any one reaction responsible for a given 

 biological effect is one of the great difficulties with which future research is 

 confronted (Zirkle, 1949). The evidence, so far, rather points to a multi- 

 tude of possible reactions which can occur simultaneously, though a con- 

 stant watch will have to be maintained for the possible emergence of a 

 reaction of outstanding significance. 



REFERENCES 



(Information on availability of government reports indicated by an asterisk may be 

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AUsopp, C. B. (1944) Radiochemistry. A review of recent progress. Trans. 

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