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W. SCHOLZ, W. SCHLOTE AND W. HIRSCHBERGER 



Fig. 8. Sharply limited total radionccrosis of semicircular shape in the brain of a 

 Syrian hamster, following the application of 30,000 r after 67 hours of survival. 

 Numerous diapedetic hemorrhages, some of them far from the necrotic zone in the 

 thalamus and midbrain. H. and E. 



hours (Fig. 8). It was not possible to identify the different types of cells in 

 the necrotic zone, which included the dorsal part of the thalamus. The 

 perikaryon had disappeared and all nuclei, including numerous polymorpho- 

 nuclear leucocytes, were in a state of pyknosis or rhexis (Fig. 9). A fairly 

 large number of small hemorrhages could be observed at some distance 

 from the necrotic zone. No progressive interstitial reaction of the glial or 

 mesenchymal tissue was seen. 



It does not seem possible to determine the pathogenesis of these necroses, 

 which have been designated as anemic by Russel ct al. (1949) because of 

 their pale appearance. We did not find occlusions of pial vessels or larger 

 arteries, and certainly the necrosis does not involve a particular region of 

 arterial irrigation. Rather, it is restricted to just the irradiated field with a 

 semicircular penetration into the depths of the cerebral tissue. To exclude 

 an ischemic condition as the cause of the necrosis, India ink was injected 

 into the left ventricle of the heart of living anesthetized animals. The freely 

 circulating blood carried the indicator substance throughout the capillary 

 bed of the area that had received 20,000 r 50 hours before (Fig. 10). In 

 some places, where erythrodiapedesis had occurred, the India ink pene- 



