NEUTRON EFFECTS ON ANIMALS 



183 



(Fig. 19). The centers of these masses of lymphocytes contained a small 

 amount of cellular debris. The amount of blood pigment present was 

 slightly increased. PohTnorphonuclear leukocytes were present at the 

 periphery of the lymphoid masses. The greatly reduced amount of h-ropho- 

 cytic tissue after 2 days corresponded to the small size of the spleen after 

 the same length of time. 



r5Pti=^s 



' % Ft -t: X- ' ~' * -' : ■■ ^ 









Fig. 

 Fig. 



17. 



IS. 





(left) (X 86) Spleen, normal. 



(right) (X 86) Spleen, 2-1 hours after irradiation with 56.4 n. 



3rd Day. The zones of lymphocytes and follicles wei-e slightl>- larger 

 than at 2 days and contained some foci of necrosis with polymorphonuclear 

 leukocytic infiltration. 



4th Day. ]Most of the cellular debris had been removed except for small 

 amounts of blood pigment. A few small scattered areas of hematopoiesis 

 were present. 



8th Day. The follicles were slightly larger than on the -1th day, but the 

 sinuses were collapsed (Fig. 20). 



16th Day. The follicles for the first time showed signs of regeneration. 

 A few small areas of blood formation were present. 



24th Day. There was active regeneration in the germinal centers of the 

 follicles. The sinuses were filled with blood (Fig. 21). 



32nd Day. The germinal centers were normal (Fig. 22) but the sur- 

 rounding zones of lymphocytes were narrower than normal. 



