448 



BIOLOGICAL EFFECTS OF RADIATION 



exposures that markedly inhibited growth of the chorda and even after 

 exposures that brought the growth of the chorda to a complete standstill 



13 

 12 



I I 

 10 



9 



. 8 



17 



6 



5 



4 



3 



2 





//y/y yy y 

 ■^^/ / ^y y 



# 



L 



-i5- 



YI Vll 



Fig. 22. — Mean growth curves for the regeneration of nonirradiated limbs in Triton 

 cristatus, following exposure of the opposite limbs to X-rays ranging from 25 to 15,000 r. 

 A'', controls. {From Brunst and Scheremetjewa, 6.) 



(Fig. 26). The optimum for showing this difference between chorda and 

 spinal cord was 2250 r. None of the exposures showed a directly stimu- 

 lating effect upon the regeneration. With 3750 r there seemed to be an 

 indirect stimulation of regeneration in the epithelium, in which it was 



75 r 

 25r 

 I50r 

 300 r 



71 MI 



Fig. 23. — Mean growth curves for the regeneration of irradiated limbs in Triton cristatus, 

 following exposure of same to X-rays ranging from 25 to 15,000 r. N, controls. (From 

 Brunst and Scheremetjewa, 6.) 



thought the degeneration products, resulting from the necrotic changes 

 in the irradiated parts, exercised the stimulating influence. 



