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HARRY F. HARLOW 



Harlow and Settlage noticed that monkeys subjected to multiple cortical 

 lesions produced by Co^° implantations frequently died from an indetermi- 

 nate cause some months afer the last implantation, without additional CNS 

 damage apparent at autopsy. Settlage also observed that monkeys, following 

 amygdaloid and periamygdaloid lesions produced by a Co*^° source, fre- 

 quently showed an exaggeration of symptoms some months after implanta- 

 tion, and frequently this terminated in death. The delayed appearance of 

 both petit mal and grand mal seizures is common in monkeys after localized 

 cerebral Co^° irradiation. 



At Wisconsin we are interested in long term effects of radiation produced 

 by both single doses and fractionated doses. We are building groups of 

 macaques that have been given 500, 600, and 700 r, if they survive it, and 

 will study biochemical, physiologic, and behavioral effects. We are tracing 

 the effects of cumulative doses of 25, 50, 100, and 200 r given to groups of 

 15 monkeys every 2 weeks. All animals are being carried to lethality with 

 the exception of the 25 r group, to which we plan to give a dose within 80- 

 90% of lethality, as determined by hematologic and physiologic measures 

 (and also behavioral measures if we can obtain adequately sensitive ones). 

 Data obtained from our 100 r group indicate that hematocrit is a sensitive 

 predictor of lethality (Fig. 1). 



The 25 r group has at present received only 550 r, and we predict that the 

 lethal radiation dose given at this rate will lie between 2,000 r and 4,000 r, 

 and that this will be the approximate range for individual monkeys within 

 the group. 



Of the 15 monkeys forming the 50 r group, we have at present 10 sur- 

 vivors. The first subject died at 900 r, and at present the surviving monkeys 

 have received 1,550 r. Twelve have been tested for retention of discrimina- 

 tion learning sets and acquisition of an oddity learning set. Six started train- 



CONTROL D-200r D-lOOr D 



Fig. 1. Hematocrit as lethal radiation dose is approached. D:= death. 



