62 THE DEFENSIVE FORCES OF THE MACROORGANISM 



immune serum, as contrasted with the instability of the opsonins of 

 normal serum when exposed to a temperature of only 56 C. for 

 thirty minutes. Subsequent investigations by numerous observers 

 have furnished additional support to Neufeld's view, the non- 

 specificity of the normal opsonins (established by myself and Lamar 

 as well as by Neufeld, Levaditi and Inman, Ritchie, Russell, and 

 others) being one of the most weighty arguments in its favor. 



This is also shown by the observation that the normal opsonins 

 are complex substances, phagocytic action depending upon the 

 joined action of two bodies, viz., a thermolabile component (opsonic 

 complement) and a second component (opsonic amboceptor) which 

 unites with the first mentioned, on the one hand, and the bacterium, 

 on the other, whereas the bacteriotropins of immune sera can act 

 independently (of complement). This difference is shown still 

 further by the different effect which normal and immune sera exercise 

 upon phagocytosis, when virulent as compared with non-virulent 

 organisms are studied in this direction; for, whereas non-virulent 

 strains of staphylococci, streptococci, pneumococci and anthrax 

 bacilli for example, readily succumb to phagocytosis in the presence 

 of fresh normal serum, highly virulent forms do so only in the 

 presence of immune serum. 



Susceptibility to Opsonification. In this connection it is interesting 

 to note that even aside from the degree of virulence, marked differ- 

 ences exist in the susceptibility to opsonification on the part of 

 different organisms. Gruber and Futaki have thus established three 

 groups in reference to their behavior toward active and inactive 

 normal serum. 



GROUP I. Bacteria which are readily taken up by leukocytes in 

 the presence of fresh serum, but not in the presence of inactivated 

 (heated) serum. 



Staphylococcus pyogenes aureus. 



Streptococcus pyogenes. 



Diplococcus pneumonise. 



Bacterium coli. 



Bacillus prodigiosus suum. 



Bacillus subtilis. 



Bacillus erysipelatosus. 



Vibrio proteus. 



Bacillus diphtherise. 



