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Fig. 2. Alpha particle radiation, 6,000 rad surface dose; sacrifice at 64 days. A. A 

 narrow band poor in granule cells lies just above an intact granular layer. Above the 

 band is a wide zone in which practically all granule cells are shrunken. Not only is 

 there cellular shrinkage, but there is also gross atrophy of the granular and molecular 

 layers in the irradiated region. Many Purkinje cells have disappeared. Glia in the 

 molecular layer have multiplied, and at the level of the band near the middle of the 

 photograph the cells of the molecular layer have disappeared. The white matter in the 

 irradiated area is pallid, and its glia ha\e increased somewhat in number. B. A nerve- 

 cell-poor band, which contains an excess of glia, stretches across the cerebral cortex. 

 The overlying cortex is greatly shrimken when comparison is made with that in Figs. 

 1 and 3 of the same magnification. Below the hand are the white matter, ventricle, 

 and hippocampus. C. From a field in the cerebral cortex, showing an atrophic band in 

 which vessels are greatly dilated. The dark structures are vessels which have under- 

 gone advanced hyalinosis. All stained by Van Gieson-hematoxylin. A and B, X 70; C, 

 X 265. 



388 



