386 



JANSSEN ET AL. 



TABLE I 



Number of Rat Brains Studied at Different Time Intervals Following 

 Irradiation with Alpha Particles and Protons " 



Time of Dosage to brain surface (in rad) 



sacrifice 50 250 750 1,500 3,000 6,000 Totals 



after A AAA A A P 

 irradiation 



Hours 1-6 — — — — — 8 2 10 



14-18 _____ 7_ 7 



20-28 _____ 13 4 17 



36-48 _____ 12 4 16 



Days 2.5-5 " _ _ _ 3 3 38 12 56 



6-11 _____ 35 25 60 



12-18 3 3 3 — — 17 5 31 



20-46 ____ 5 3 6 14 



64 43 3 3 3 9 — 25 



120 _____ 1 _ 1 



150 _____ 1 _ 1 



216 3 2 3 3 3 2 — 16 



10 8 9 9 14 153 58 261 



" Key: A, alpha paitirle radiation; P, pioton radiation. 



TABLE II 



Width of Region of Damage in the Cerebellu.m and Cerebrum Following 

 Exposure to Alpha Particles and Protons at 6,000 Rad Surface Dose 



Site of irradiation 



Alpha particles 



Protons 



Zone (fji) Band (^) Zone (fj.) Band (^) 



Cerebellum 



average width 

 Cerebrum 



average width 



6 hr-5 days 7-216 days 6 hr-6 days 7-30 days 

 110 41 123 45 



24 hr-7 days 8-216 days 60 hr-6 days 7-30 days 

 236 110 291 119 



On the other hand, the width of the zone and of the band was less for the 

 cerebelkim than for the cerebrum by a factor of around 2/2- Due to the 

 factor of tissue shrinkage as a consecjuence of irradiation, the width of the 

 zone or band decreased with time. With respect to alpha particles, for ex- 

 ample, the average width of the zone in the cerebellum during the 6 hour- 

 5 day period was 110 /m. and at the 7-216 day period, 41 /x, at which time 

 the "zone" had shrunk to form a "band."" In the brains exposed to a 3,000 

 rad surface dose, the series was too small to obtain dependable averages. 

 However, the width of the band was substantially less (Fig. 1 -4 ) . 



