Further Studies on the Effects of the Removal of the Chief Lymphoid Organs

1. In a series of the young adult albino rats the chief lymphoid organs (thymus, spleen mesenteric lymph nodes and other small lymph nodes) were extirpated. The total amount of the removed lymph nodes amounted to about 85 pre cent or more of the entire lymph nodes. 2. Such an extensive extirpation of the lymphoid tissue produced a pronounced and persistent lymphopenia. Though the normal blood lymphocyte level was not reestablished until 10 months after operation, the operated animals showed no abnormality in their general body growth.　　　　　　　　　　　　　　　3. There was observed a marked hyperplasia of lymphatic tissue in the remaining lymph nodes, in the Peyer' s patches and of the peribronchial lymphoid tissue in the lung at 6months as well as at 10 months after operation. In addition, there occurred a new formation of lymphocyte aggregations in the periportal spaces of the liver. The regeneration of lymph nodes, however, did no take place at the site of extirpation. 4. The above-mentioned compensatory mechanism foe the ablation of lymphoid tissue was substantiated by chemical determinations of DNA-P content in these tissues, which indicated a significant increase in DNA-P content per organ and per 1 gram fresh tissue, not only in the Payer's patches and lung but also in the liver.