264 



H. HAGER, VV. HIRSCHBERGER AND A. BREIT 



Fig. 3. Cerebral cortex, 48 hr after exposure to 45,000 r. A diapedetic erythrocyte 

 (E) lies between completely intact cell processes in the neighborhood of a capillary. 

 EC, swollen endothelial cytoplasm; EN, endothelial nucleus; O, outpouching in the 

 capillary lumen; B, basement membrane of capillary. X 10,800. 



thelium. Occasional outpouchings and irregularities in the capillary lumen 

 can also be seen. Cytoplasmic organelles and vascular basement membranes 

 show no significant alterations. 



Similar changes in the blood vessels and remarkable edematous astrocytes 

 are also noted in irradiated cerebellar tissue (Fig. 4). Here, however, nerve 

 cells are also involved, though there is a striking difference in the appearance 

 of granular cells and Purkinje cells. The latter are relatively unchanged, 

 while the granular cells are shrunken and hyperchromatic with clumping of 

 the nuclear material. A higher magnification of such changes is seen in 

 Fig. 5, where normal and abnormal granular cell nuclei can be contrasted. 

 These pyknotic changes in granular cells following radiation have been 

 recognized by several investigators (Alvord and Brace, 1957; Briinner, 1920; 

 Haymaker ct ai, 1954, 1958; Schummelfeder, 1957: Vogel et al., 1958), and 

 similar electron micrographs have been published by Vogel (1959). 



In Fig. 6 the extensive plasma exudation following radiation is apparent. 

 The perivascular space bounded by the glial and vascular basement mem- 

 branes (Nelson <7 ai, 1961 ) is filled with structureless material, which has 

 a density similar to that of plasma and contains inflammatory cells. Neither 

 leucocytes nor erythrocytes have so far been seen penetrating the glial base- 

 ment membrane that constitutes the external margin of the perivascular space, 



