PATHOLOGIC CHANGES IN BRAIN CAUSED BY ALPHA PARTICLES 403 



band of damage there were minute hemorrhages and extravasates of globu- 

 lar proteinaceous material. Between 5 and 8 days, vascular dilatation was 

 more evident (Fig. 13A), and a fair number of reactive cells had appeared 

 in the sheaths of vessels in the nerve-cell-poor band and somewhat higher. 



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Fig. 13. Radiation. 6.000 rad surface dose. Pickworth-Lepehne preparations. A. (8 

 days) .\lpha particle radiation. \'ascular dilatation is to be seen in the irradiated part 

 of the cerebellum and cerebrum, and in the latter is most apparent in the region cor- 

 responding to the peak and upper slopes of the Bragg cur\e. X6. B. (9 days) Proton 

 radiation, .\neurysmal vascular dilatation and multifocal lack of erythrocyte staining 

 are to be noted. Occasional hemorrhages ha\e occurred. X50. 



