224 



INFECTION AND IMMUNITY. 



Two Stages in 

 Agglutina- 

 tion. 



Group Ag- 

 glutination. 



are still present in such quantity that agglutina- 

 tion is brought about. 



The presence of some salt is necessary for the 

 occurrence of agglutination. Bordet found that 

 if the salts were removed from the serum and from 

 the suspension of bacteria by dialysis, and the two 

 were then mixed,, agglutination did not occur; if 

 a small trace of sodium chlorid was added the re- 

 action took place promptly. Furthermore, if the 

 serum was completely removed from the bacteria 

 by repeatedly washing them in distilled water, it 

 was found that the microbes had absorbed the ag- 

 glutinin, but the latter remained inactive until the 

 salt was added. 



This experiment not only suggests a haptophor- 

 ous as distinguished from a zymotoxic group, but 

 also indicates that agglutination consists of two 

 phases. The first phase represents the union of 

 agglutinin with the bacteria, while in the second 

 are included the other changes necessary for the 

 clumping of the organisms, in which the activity 

 of the zymotoxic group is represented. The action 

 of the salt, just cited, is unknown. 



The properties of serums which are of interest 

 in immunity are now being studied by chemists, 

 notably by Arrhenius. The study of mass action, 

 of chemical equilibrium between agglutinin and 

 agglutinogen, for example, and of the dissociation 

 of the compound after it has once formed, are 

 subjects under investigation, but which are too 

 technical to be entered on here. 



"Group agglutination" has been referred to. By 

 this is meant the ability of an antimicrobic serum 

 to agglutinate certain other organisms which mor- 

 phologically, biologically and often pathogeneti- 



