RADIATION IN PRENATAL DEVELOPMENT 



875 



data indicate that the slope of the dose-mortality curve for any given 

 stage is steep around 50 per cent lethality (see also Fig. 13-96). The 

 work of both Kaven and Russell makes it clear that mortality is markedly 

 dependent on the stage irradiated, even when stages are separated by only 

 ioo- 



90- 



80- 



70- 



< 



uj 60 



Q 



_l 

 < 



< 



o 



Ld 



o 



50- 



40 



30- 



20- 



10- 



• 300 r 

 O 200 r 



DAY IRRADIATED (POSTCONCEPTION) 

 Fig. 13-2. Incidence of neonatal death following irradiation with different doses at 

 different stages in the prenatal development of the mouse. {Data of Russell and 

 co-workers.) 



24-hour intervals. For the data presented in Fig. 13-2, the LD 5 o at birth 

 varies as follows according to the stage irradiated: 



For irradiation on days ^-S^ postconception, LD 5 o > 200 r. 

 For irradiation on days 9^ and 10^ postconception, LD 50 < 200 r. 

 For irradiation on day 11^ postconception, 200r < LD 5n < 300r. 

 For irradiation on days 12^-15% postconception, LD 50 >300 r. 



