DNA AND Effects of Radiation and Peroxides 285 



Dr. C. C. Brinton, illustrates this finding: 7 minutes after 

 infection, B-T2 monocomplexes growing at 37° C in synthetic 

 56 medium, are mixed with 10* cumene peroxide. After 

 5 minutes of contact, the suspension is diluted 1000-fold in 

 buffer. From time to time 0-1 cc. is spread: 



(a) on broth agar supplemented with catalase, in the 

 presence of an excess of bacteria grown in broth ; 



(b) on 56 agar in the presence of the minimum number of 

 bacteria required to give plaques. 



After incubation, the number of plaques gives the number of 

 surviving complexes plus a few free T2. The number of the 

 latter is determined in parallel controls which have been 

 plated after elimination of the complexes by chloroform 

 treatment (Table III). 



One sees that the number of survivors in the (b) series is 

 almost constant and very soon reaches the minimum which, 

 in the (a) series, is obtained only after 100 minutes, during 

 which a constant posteffect shows up. 



It appears likely that this posteffect is similar to that 

 observed after radiation treatment. This conclusion reinforces 

 the idea that the radiation posteffect is mediated by radio- 

 formed organic peroxides. However, the possibility is not 



