504 BROWN, SASMORE, AND JONES 



In the first study at the Nevada Test Site in 1957, which was reported 

 in detail (Kuhn and Kyner, 1958), 88 burros were exposed to prompt 

 neutron-gamma radiation from a nuclear detonation. They were divided 

 into groups of eight and placed in steel culvert shelters, 5 feet in diameter 

 and 13 feet in length, designed to hold 2 animals placed nose-to-nose and 

 broadside to the nuclear device. Four shelters each were placed in 11 regu- 

 larly spaced rows at a distance from ground zero calculated to bracket the 

 median lethal dose of prompt radiation. The dose range (air) was 250 to 

 780 rep with a neutron/gamma ratio of approximately 1. 



In the second study (Kuhn and Brown, 1960) on head irradiation, 25 

 male burros were exposed to a single Co*"' source with the brain as the 

 principal target. The dose rate was approximately 100 r per minute. The 

 animals were lightly anesthetized and placed in a lateral recumbency with 

 the head positioned so that the midpoint of the brain was 9 cm from the 

 source, as determined by topical reference points. The animals were exposed 

 in groups of five in a sequential dose pattern (dose range 150-1,200 r) 

 described by Mewissen (1958). 



In the third study (Thomas and Brown, 1960), which was designed to 

 study sodium activation in the blood, 7 male burros were exjxjsed unilater- 

 ally to Godiva II (bare reactor) at the Los Alamos Scientific Laboratory. 

 The animals were positioned with their right side 3 meters from the center 

 of the reactor. Each animal was restrained in a crate to maintain constant 

 position. The dose of 180 rad was delivered at 6 rad per minute. 



All tissues were fixed in 10% buffered formalin, imbedded in paraffin, 

 sectioned at 5 jx, and stained with hematoxylin-eosin. Sections from the 

 central nervous system included cerebral hemispheres, pituitary, hypothala- 

 mus, thalamus, p>ortions of the ventricles, corpora quadrigemina, medulla, 

 cerebellum, and hippocampus. 



Results 



Mortality 



Burros in each experiment died early. All deaths occurring within 120 

 hours after exposure were associated with pronounced neurologic symptoms. 

 Forty-five of the 55 acute deaths in the Nevada study and all deaths in 

 the head-irradiation and Godiva studies occurred within 120 hours after 

 irradiation. 



Neurologic Symptoms 



Following irradiation the animals appeared normal for 2-10 hours; then 

 an abnormal behavior pattern ensued. 



