4 QUATERCENTENARY STUDIES IN PATHOLOGY 



the London Hospital. Many of the alveolar spaces were filled with 

 blood, and lying amongst the red cells could be seen mononuclear 

 leucocytes closely packed with red blood cells. 



Much interest, too, is lent to this subject by the close relationship it 

 bears to some other phenomena, which are due to the action of certain 

 body fluids, especially to haemolysis and agglutination. Of late a 

 considerable amount of discussion has arisen with regard to the relation- 

 ships of these various phenomena one to another, and in the course of 

 this, much light has been thrown on various questions in connection with 

 the immunity problem. 



The histories of haemolysis and of phagocytosis, especially of red 

 blood cells, are so closely bound together that it may be useful to 

 recount briefly the various stages in the evolution of our knowledge of 

 these phenomena. 



The pioneer in this work was Metchnikoff, and although much of his 

 work on the subject has been controverted, yet there can be no doubt 

 that his ideas and observations acted as a great incentive to research on 

 this problem. His work and that of his pupils will repay examination. 



Metchnikoff's Views on Macrophages and Microphages. 



In the course of his observations on phagocytosis, Metchnikoff was 

 led to the conclusion that various atrophic processes, such as progressive 

 muscular atrophy, senile atrophy, greying of hair, &c., were to be 

 attributed to what he termed the phagocytic action of certain of the 

 body cells. The metamorphosis of various insects and amphibians he 

 considered to be due to the same cause. These processes he attributed 

 almost entirely to the action of macrophages, a term which he employed 

 to designate such cells of the fixed tissues as might take on a phagocytic 

 action for animal cells, and the large mononuclear leucocytes. The 

 polymorphonuclear leucocytes he termed microphages, and to these he 

 attributed the power of engulfing micro-organisms. 



Metchnikoff's Theory of Cytases and their Origin. 



He showed, too, that when one injects blood or other alien cells into 

 the peritoneal cavity or under the skin of animals, phagocytosis of these 

 cells ensues, the phagocytic agents employed being almost exclusively 



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