EFFECTS OF HEAD IRRADIATION IN NEWBORN RATS 



61 



lOOOn 





800- 



600 



400- 



200- 



/ 



t- 



4 6 8 10 



DAYS AFTER BIRTH 



14-17 



Fig. 1. A graph showing a dose-age cur\c with respect to tlie production of neu- 

 rologic signs by head radiation in the neonatal rat. Most of the animals to the left of 

 the cur\e had clinical signs in\ol\ing the ner\ous system, while most of the animals 

 to the right of the cur\e did not. (From CUcmente et a!.. 196(1. p. 670.) 



sexerity of neurologic signs, and radiation on the 15th day resulted in no 

 visible neurolotiic findings. e\en thouy h doses of 1 .000 r were administered 

 (Fi,o-. 1). 



Similar a^e-dose relationship was demonstrated in regard to mortality, 

 retardation of body growth, head growth, and cataract formation. Tremor 

 was the most frecjiiently obser\ed neurologic sign and appeared as early as 

 the 2nd week in animals irradiated with 1.000 r during the first 5 days 

 postnatally. Other neurologic findings were incoordination, paresis, a pe- 

 culiar propulsixe gait, and falling backward when animals attempted to 

 stand on their hind legs. Seizines occurred in a few animals. Small heads 

 were noted in 23 cases. Cataracts dexeloped in 7 rats. 6 of whom had small 

 heads, and the greatest incidence of cataract formation occurred in animals 

 that had received 500 r on the 5th day. It is possible that a higher incidence 



