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RADIATION BIOLOGY 



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Fig. 17-2. Three stages in the degeneration and beginning regeneration of lymphatic 

 tissue of mesenteric lymph node of rabbits after total-body irradiation with 800 r of 

 200-kv X rays. (A), untreated rabbit, shows an active germinal center with the shell 

 of small lymphocytes extending into the dense diffuse lymphatic tissue. (B) 17 hours 

 after irradiation, all the lymphocytes in the nodule have been destroyed and many of 

 those at its periphery are also degenerating. Most of the debris is within macrophages, 

 especially in the center of the nodule. (C) 24 hours after irradiation; except for a few 

 scattered lymphocytes, the nodule consists mainly of reticular cells and a few lympho- 

 cytes, both large and small. (D) 31 days after irradiation; there is a focus of intense 

 formation of lymphocytes (a new nodule) and beginning repopulation of the diffuse 

 tissue with lymphocytes. (After De Bruyn.) 220 X. 



