REACTION OF THE HOST TO INFECTION 



215 



points. It is also called intermediary body, immune body and 

 sensitizer. The other component of the lytic complex, which 

 is thermolabile and which is present in normal serum, is called 

 complement or cytase, and by some authors (Bordet) alexin. 1 

 It will be noted that only a part of the cytolysin is produced 

 by the body in its reaction to invasion, namely, the immune body. 

 Deviation of Complement. Neisser and Wechsberg observed 

 that the bactericidal power of a given immune serum (bacteriolytic 

 amboceptor), when combined with a constant amount of normal 

 serum (complement) and a constant amount of a bacterial sus- 

 pension (antigen), increased progressively with progressive 

 dilution of the immune serum to a certain point, after which it 

 diminished again. The following data taken from Citron illus- 

 trate the experiment: 



Neisser and Wechsberg have undertaken to explain this 

 result by supposing that the excessive number of amboceptors 

 present in the more concentrated solutions of immune serum 

 hinders cytolysis because some of them combine with the antigen 

 by means of their cytophile groups while others are combining 

 with the complement by means of their complementophile 

 groups, and as a result the mixture contains combinations of 

 amboceptor with antigen, and of amboceptor with complement, 

 but practically no combinations of the three elements together. 

 There are grave reasons for questioning the accuracy of this 



1 This use of the term alexin would seem to be undesirable, for Buchner employed 

 the term to designate the whole bactericidal or cytolytic complex before the possi- 

 bility of recognizing two separate elements was clearly recognized. 



