222 



GENERAL BIOLOGY OF MICRO-ORGANISMS 



present in normal serum is called complement or cytase and 

 by some authors (Bordet) alexin. ^ 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 illustrate ' 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 complem en tophile groups, 

 and as a result the mixture contains combinations of amboceptor 

 with antigen, and of amboceptor with coinplement, but practically 

 no combinations of the three elements together. There are 

 grave reasons for questioning the accuracy of this assumption, 



' 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. 



