416 



CLEMENTE AND RICHARDSON 



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Fig. !3. In these 5 pictures are examples of some acute vascular and perivascular 

 reactions in various areas of the brain after head x-irradiation in monkeys. (250 kv, 

 half-value-layer for filtration of 0.5 mm Cu and 1.0 mm Al was 1.4 mm Cu; mid- 

 cranial focal distance 35 cm; Dosage rate 118 r per min.) Thionin, H. and E., 

 and Van Gieson stains. (A.) Petechial hemorrhage in white matter of occipital cortex, 

 8 hours after 4,500 r. X 175. (B.) Perivascular leucocytic reaction in medulla 36 hr 

 after 6,000 r. X 175. (C.) Perivenous reaction in the lateral hypothalamus 8 hr fol- 

 lowing 4,500 r. X 140. (D.) Red and white blood cell diapedesis in the caudate nu- 

 cleus in a monkey 8 hr following 6,000 r. X 85. (E.) A severe perivascular leucocytic 

 infiltration in the parietal cortex 6 hr following 4,500 r. X 85. 



accelerated penetration of Na-* into the brain and cerebrospinal fluid in 

 the radiated animals, even though histologic changes were minimal even 

 at 1,500 r. 



