]88 Prof. Muir and Mr. Martin. On the Combining [Jan. 18, 



found that just as complements in their combining affinities do not possess 

 specific properties, but are absorbed by a great many different substances, 

 so also these thermolabile opsonins show a corresponding community in their 

 combining relationships. We, however, expressly left out of consideration 

 the special opsonins of immune sera, and also the thermostable opsonins 

 of normal sera, of which latter the stable opsonin of human serum for the 

 diphtheria bacillus may be taken as an example. In the present communi- 

 cation we shall consider the thermostable opsonins of immune sera. 



It is unnecessary to enter in detail into the literature of the subject, 

 as this has been already done by Dean.* It is, however, advisable for the 

 sake of clearness to refer to the chief facts which have been established and 

 to the chief points at issue. It is now a considerable time since Metchnikoff 

 showed that the establishment of active immunity towards various bacteria 

 was often accompanied by increased 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 Lecleff showed in the 

 case of rabbits immunised 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 DouglasJ were the first to show that 

 phagocytosis by leucocytes in the presence of normal serum depended upon 

 certain thermolabile 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,§ by Hektoen and 

 EuedigerJI 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 

 mentioned those of Savtchenko,1F Neufield and Rimpau,** Dean,ft 

 Leishman,tJ and others. And Wright and Eeid§§ have shown that in 



* Dean, ' Roy. Soc. Proc.,' vol. 76, p. 515. 



t Denys and Leclef, ' La Cellule,' 1895, p. 177. 



X Wright and Douglas, ' Roy. Soc. Proc.,' vol. 72, p. 357. 



§ Bulloch and Atkin, ' Roy. Soc. Proc.,' vol. 74, p. 379. 



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



1 Savtchenko, ' Annales de l'lnst. Pasteur,' 1902, p. 106. 

 ** Neufield and Rimpau, ' Deutsch. Med. Wochenschr.,' 1904, p. 1458. 

 tt Dean, op. cit. 



H Leishman, 'Path. Soc. Trans.,' 1905^ 

 §§ Wright and Reid, ' Roy. Soc. Proc.,'' vol. 77, p. 211. 



