876 



RADIATION BIOLOGY 



2. BODY SIZE 



Although only a few investigators report observations on weight or 

 length of their material, the information available is sufficient to demon- 

 strate an effect on body size of irradiation during the period of major 

 organogenesis. Kosaka (1928b, c, d) mentions generalized hypoplasia 

 from prenatally lethal doses in several rodents. Wilson and Karr (1951) 

 present data on prenatally observable growth retardation in rat embryos. 

 Raynaud and Frilley (1949a) and Russell (1950), both working on mice, 



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DAY IRRADIATED ( POSTCONCEPTION) 



• 200 r O 300r A 400 r 

 Fig. 13-3. Mean birth weights following irradiation with different doses at different 

 stages in the prenatal development of the mouse. (Russell, 1950.) 



have measured size at term. Finally, there are two rather vague reports 

 of reduced body size in later life, in the rat (Hanson, 1923), and the 

 rabbit (Cohn, 1907). 



Wilson and Karr (1951) found no effect on body weight 2-11 days after 

 irradiation with 50 r on day 10. With 100 r, however, there was a 

 marked growth retardation one day after irradiation, treated embryos 

 weighing 37 per cent less than controls. This high initial retardation 

 may have been due mostly to moribund embryos since the percentage 

 weight reduction in survivors decreased to between 6 and 15 per cent in 

 the succeeding period up to term. With 200 r, weight reduction 

 decreased to 20 per cent in survivors after an initial high of 39 per cent. 

 Finally, embryos irradiated with 400 r, all of which were already dead at 

 the time of first observation, appeared to have undergone at least some 



