50 



ROBERT H. BROWNSON 



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10 



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Fig. 8. Cerebral cortical arteriole demonstrating hypertrophy and hyperplasia of ad- 

 vcntitia with large hyperchroniatic nuclei 228 days following 1.820 r. VerhoeflP: 

 X 64. 



Fig. 9. Normal rat hypothalamus and third \entricle. VerhoefF; X 130. 



Fig. 10. Hypothalamus with increased vascularity and perivascular connective tissue. 

 Increased numbers of nuclei 228 days following 2,000 r. VerhoeflF; X 130. 



Fig. 11. Hypothalamus with increased vascularity and perivascular connective tis- 

 sue. Numbers of nuclei present less than demonstrated in Fig. 9 228 days following 

 5,000 r. VerhoeflP: X 130. 



nearly all cases there was a favorable increase in the \veia;hts approximately 

 one week followino; the last exposure administered to that group. One 

 notable exception was in oioup G after reaching the 5,000 r level. This 

 group failed to show any tendency to increase weight imtil after 120 days. 



