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The Lymphocyte and Lymphocytic Tissue 



Phagocytosis 



Phagocytosis is an important function of exudate cells. No lesser an in- 

 vestigator than Metchnikoff in 1888 1 first demonstrated that blood lympho- 

 cytes in experimental animals migrated to the areas infected with tubercle 

 bacilli, gradually hypertrophied, and formed macrophages and epithelioid 

 cells. Although more positive information has been published to support 

 this thesis, rather than to deny it, many textbooks of pathology have ex- 



Fig. 6-1. Lymphocytic infiltrations in chronic parenchymatous syphilitic encephali- 

 tis (paresis). Nissl's stain. (X 375) 



eluded the hematogenous (lymphocytic) macrophages as part of our general 

 defense system of cells. This can be traced in part to the so-called German 

 school of thought typified by Aschoff. In 1913 he and Kiyono published 

 their work 2 on the "large mononuclears" and did not mention the lympho- 

 cyte because, under the conditions of their experiments, it did not store 

 vital dyes. 



Another objection was the belief that lymphocytes were incapable of 

 ameboid motion and, therefore, could not migrate from the vessels into 



