446 



BIOLOGICAL EFFECTS OF RADIATION 



inhibitive effect, but the results were so diversified in all the experiments 

 that differences in the reactions of the individuals to the same exposure 

 became apparent. For this reason the authors concluded that a larger 



a 





m 



If Da 



15,000 r 

 I 11 



3,750 r 

 1 II 



l,500r 

 I II 



750 r 

 I II 



300r 

 I II 



150r 

 I II 



75 r 

 I II 



25 r 

 I II 



^4 



^3U4 



9 



-rv^ 



6; 



51 



w* 



4-^ 



12 



10 



6 



4 29 T\ 



31 21 



10 10 



30 21 22 18 25 20 9 8 



Fig. 18. — Graphic representation of the effects of various X-ray exposures upon regen- 

 eration of the limbs of the irradiated side of Triton cristatus. Each pair of columns repre- 

 sents an exposure, the number above the pair representing the roentgen units. Column I 

 represents the first regeneration; Column II, the second. The numbers below the columns 

 show the total number of individuals at conclusion of any experiment. The numbers 

 within the columns show the number of individuals giving the reactions designated a to g. 

 The shading indicates these reactions as follows: a, no regeneration; h, reduction; c, regen- 

 eration and reduction; d, insignificant regenerative growth; e, significant delay of 

 regeneration; /, insignificant delay of regeneration; g, normal regeneration. (From Brunst 

 and Scheremetjewa, 6.) 



number of specimens than were used in each experiment by Litschko (40) 

 is necessary for trustworthy conclusions (Figs. 22 and 23). They 

 .explained this difference of reactions in terms of the capacity of individual 

 organisms to react differently to the same external factor and the com- 

 plex effect of irradiation involving primary and secondary factors as it 



does in an animal with such 

 a degree of organization as the 

 salamander. In studying the 

 persistent effects of the irra- 

 diation, it was observed in 

 cases of stronger exposure 

 that where the first regenera- 

 tion of any appendage showed 

 a conspicuous effect its second regeneration usually showed an even 

 stronger effect; and that where the first regeneration was not conspicu- 

 ously affected its second regeneration was affected to an even smaller 

 degree (Figs. 18, 20, and 21). 



Fig. 19. — Effect of X-rays (1500 r) upon regen- 

 eration of hind limbs of Triton cristatus. a, ventral 

 view 17 days after exposure of the right and amputa- 

 tion of both these limbs; b, dorsal view of same 

 specimen 34 days after; c, dorsal view of same 51 

 days after. (From Brunst and Scheremetjewa, 6.) 



