176 CORTEX 



markedly enlarged. The immediate cause of this hyperplasia, 

 like that of the thymus, is unknown. Banting and Gairns 31 

 described an enlargement of the lymph nodes in dogs accom- 

 panied by a proliferation of plasma cells, endothelial leucocytes, 

 enlarged macrocytes, and a great increase in the reticular tissue, 

 with obliteration of the germinal centers. McMahon and 

 Zwemer, 420 on the other hand, describe the change in cats as 

 consisting of an enlargement of the germinal centers which are 

 filled with young lymphocytes and lymphoblasts showing ac- 

 tive mitosis. 



As to the significance of the status lymphaticus observed in 

 adrenal insufficiency several possible explanations may be pre- 

 sented. Kahn 343 suggested that it is a compensatory mechanism 

 to counteract a primary injury to the myelo-erythroblastic 

 system. Marine and Jaffe 335 suggested that the hyperplasia 

 of the thymus is a response to hyperthyroidism induced by 

 adrenal insufficiency. It is true that in hyperthyroidism (as 

 well as in hypothyroidism) one observes hyperplasia of the 

 lymphatic tissues. However, as shall be shown in Chapter 

 XIII, adrenalectomized animals maintained on an inadequate 

 dose of cortical hormone show no signs of hyperthyroidism. 

 In fact, they manifest the symptoms of a depressed thyroid 

 function. It is consequently difficult to accept the hypothesis 

 that the hyperplasia of the thymus is a response to hyperthy- 

 roidism induced by adrenal insufficiency. It would be more 

 logical to ascribe the observed hyperplasia to the thyroid in- 

 sufficiency which is secondary to chronic cortical insufficiency 

 (Chapter XIII). However, until our knowledge of the exact 

 function of the thymus and other lymphatic tissues is eluci- 

 dated, it is futile to speculate concerning the significance of 

 their hyperplasia in adrenal insufficiency. 



PANCREAS 



Congestion of the pancreas is one of the commonest findings 

 at autopsy of animals dead of adrenal cortical insufficiency. 



