OPSONIC ACTION 173 



points at issue. It is now a considerable time since Metchni- 

 koff showed that the establishment of active immunity 

 towards various bacteria was often accompanied by in- 

 creased phagocytic action on the part of leucocytes and 

 other cells, or by the appearance of phagocytic action when 

 this was absent under natural conditions. Denys and Leclef 1 

 showed in the case of rabbits immunized against streptococci 

 that the increased phagocytosis was due not to changes 

 induced in the leucocytes, but to an alteration in the serum, 

 and pointed out that the leucocytes of the immune animal 

 when placed in a normal serum showed no greater phagocytic 

 activity than normal leucocytes did. Wright and Douglas 2 

 were the first to show that phagocytosis by leucocytes in 

 the presence of normal serum depended upon certain thermo- 

 labile substances ' opsonins ' in the serum which became 

 fixed to the bacteria in question and made them a prey to 

 the leucocytes. Their results were confirmed by Bulloch 

 and Atkin, 3 by Hektoen and Ruediger, 4 and by others, and 

 may now be accepted as established beyond question. We 

 have, on the other hand, a large group of observations 

 which show that in immune sera the substance which leads 

 to the phagocytosis of bacteria, or of red corpuscles, as the 

 case may be, is thermostable, i. e. resists a temperature of 

 55 C. for an hour. Among such observations may be men- 

 tioned those of Savtchenko, 5 Neufeld and Rimpau, 6 Dean, 7 

 Leishman, 8 and others. And Wright and Reid 9 have 

 shown that in certain cases the serum of patients suffering 

 from tuberculosis may contain a considerable proportion of 



1 Denys and Leclef, La Cellule, 1895, p. 177. 



* Wright and Douglas, Roy. Soc. Proc., vol. Ixxii, p. 357. 



3 Bulloch and Atkin, Roy. Soc. Proc., vol. Ixxiv, p. 379. 



4 Hektoen and Ruediger, Journ. of Infectious Diseases, 1905, p. 128. 

 6 Savtchenko, Annales de VInst. Pasteur, 1902, p. 106. 



' Neufeld and Rimpau, Deutsch. Med. Wochenschr., 1904, p. 1458. 



T Dean, op. cit. 8 Leishman, Path. Soc. Trans., London, 1905. 



Wright and Reid, Roy. Soc. Proc., vol. Ixxvii, p. 211. 



