132 The Lymphocyte and Lymphocytic Tissue 



Unfortunately quantitative data for other species are not available, although 

 such curves are essential to extrapolate data to the human species. 



Vogel and Ballin determined the weight of the rat thymus 24 hours 

 after irradiation with varying dosages. 62 After 400 r the decrease in weight 

 was 59 per cent. After 30,000 r the disease was only 10 per cent. The larger 

 dose produced less effect than the smaller. In addition, they observed that 

 fewer pyknotic nuclei were found in the thymus 24 hours after irradiation 

 with 20,000 r than after 400 r. A similar histologic finding was obtained by 

 Trowell, Corp, and Lush for the thymus but not for lymph nodes. 60 



These interesting and paradoxical findings in vivo may be explained by 

 the in vitro observation that higher doses of x-rays (2,000 r or more) pro- 

 duced death by delayed fixation"' while lower doses such as 400 r produced 

 death by intranuclear vacuolization and pyknosis. 40 The decrease in the 

 weight of the organ depends not on the death of the cells but on the removal 

 or absorption of the dead cells by phagocytosis and autolysis. In the thymus, 

 phagocytosis and removal of pyknotic nuclei are slower than in the spleen. 36 

 The fixed cells produced by the irradiation of the thymus with 20,000 r are 

 probably less readily absorbed than the cells with pyknotic nuclei produced 

 by 400 r. 



Blood Lymphocytes. Associated with the rapid destruction of lympho- 

 cytes in the lymphoid tissue is a rapid decrease in the blood lymphocytes 

 following radiation. In rabbits given total body irradiation, the lymphocyte 

 count decreased rapidly and reached a minimum count in 24 to 48 hours 

 (Fig. 10-8). 46 In men who were accidentally exposed to total or almost total 

 body irradiation, the lymphocyte count decreased more slowly, and it took 

 one to five days for the count to reach a minimum. 16 Accidental total body 

 exposure of 64 individuals to 175 r reduced the lymphocyte count to 

 25 to 55 per cent of the control in three days. 10 



Lymphopenia also developed after therapy of patients for cancer with 

 x-rays or radium. 1 "'' -"' The lymphopenia developed irrespective of which 

 part of the body was irradiated. Surface irradiation, however, with beta rays 

 had no effect on the blood cells. 44 The important factors in the production 

 of lymphopenia after therapy were the dose and the volume or weight of 

 the part of the body irradiated. Therefore some workers advocate the use 

 of the integral dose which is defined as the dose multiplied by the estimated 

 weight of irradiated tissues. A dosage of 7 to 10 megagram roentgens was 

 found to depress the lymphocyte count to 25 per cent of the original. 24 



Price and others analyzed mathematically the rate of fall of lymphocytes 

 in irradiated humans and animals. 4 -' 4G According to Goodfellow, 15 the rate 

 of decrease of lymphocytes varied directly with the dosage of radium. How- 

 ever, treatment with 10,000 mgh. or more produced a maximum 11 per cent 

 daily decrease during the first 7 to 10 days of treatment. 



