ANTIBODIES TO PNEUMOCOCCUS 405 



immunity. According to the latter authors, actively immunized 

 mice manifested the same specific phagocytosis as those passively 

 immunized, but scarcely ever had demonstrable protective bodies 

 in the blood. However, after intravenous injection of manganese 

 salts, the protective substances appeared in the blood in large 

 amounts. Neufeld and Meyer concluded that the active immunity 

 depended entirely upon antibodies, that the antibodies were formed 

 in the reticulo-endothelium and that, in a broader sense, the cells 

 of the Gefassbindegewebsapparat were the sole source of anti- 

 bodies. 



The ability of macrophages to dispose of pathogenic bacteria 

 was described by Nakahara (1925). 941 The method of demonstrat- 

 ing the action of these cells was the injection of olive oil into the 

 peritoneal cavity of mice. The injection was followed at first by 

 the appearance of polymorphonuclear leucocytes, which were 

 largely replaced by mononuclear cells. When pneumococci were in- 

 jected into mice during the macrophagic reaction, the organisms 

 were destroyed more rapidly than was the case in normal animals, 

 and the mice survived multiples of the minimal infecting dose. The 

 macrophages were observed to phagocyte the injected cocci ac- 

 tively. 



Meyer (1926), 896 after blocking the reticuloendothelial system 

 by the intravenous injection of ferric saccharate, India ink, trypan 

 blue, and other dyes, along with the removal of the spleen, was 

 unable, as a rule, to immunize mice by the injection of killed pneu- 

 mococci of Type I. When active immunization preceded the re- 

 moval of the spleen and the injection of the blocking agents, the 

 immune condition of the animals was sometimes altered. Meyer 

 was not able to substantiate the earlier observation of Neufeld 

 and Meyer on the necessity of stimulating the endothelia by man- 

 ganese, since protective antibodies were found to be present in the 

 blood of the majority of mice immunized with Type I pneumococci. 

 Inasmuch as splenectomized mice in which the reticulo-endothelial 

 system had been blocked easily acquired passive protection after 



