DNA AND Effects of Radiation and Peroxides 291 



leaving 10 per cent or less of active units, the inactivation 

 of which proceeded exponentially also, but at a much 

 lower rate (Fig. 5). This remarkable feature has been 

 constantly observed in the inactivation of the same TP 

 either by u.v. (Latarjet and Cherrier, unpubhshed) or 

 by X-rays. The parallelism between X-radiation and 



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 Fig. 5. Inactivation of TP/sr by succinic peracid. 



peroxide is, here again, so striking that the results 

 obtained with the former acting by direct effect on the 

 same material should now be^ mentioned, with special 

 emphasis on the radiobiological aspect of this work. 



Inactivation of a transforming agent by the direct 



effect of X-radiation 



This work has already disclosed a number of facts which 

 have been or will be published in detail (Ephrussi-Taylor and 



