160 



INFECTION AND RESISTANCE 



either chemical affinity by means of a definite atom group or a mere 

 physical change of molecular equilibrium permitting a specific com- 

 plement absorption. 56 



It will be seen from the preceding that the controversy between 

 Ehrlich's "amboceptor" conception and the "sensitization" idea of 

 Bordet turns largely upon the existence of a so-called complemen- 

 tophile group of the thermostable antibody. For if it were the case 

 that this antibody possessed an atom group which permitted it to 

 unite with alexin, independent of previous union with antigen, it 

 would go far to support Ehrlich's view. One of the strongest argu- 

 ments brought into the field in favor of such an occurrence by Ehr- 

 lich's followers is the phenomenon of Neisser and Wechsberg, which 

 is usually spoken of as "complement deviation" (Komplement Ablen- 

 kung). 



In order to make the conditions underlying this phenomenon 

 clear, it will be of advantage to consider for a moment the methods 

 of determining quantitatively the amount of bactericidal antibody 

 (sensitizer amboceptor) in any given immune serum, since it was in 

 working with such titrations that Neisser and Wechsberg made their 

 observations. 



In carrying out such measurements, -it is customary to add in 

 series, to constant amounts of bacteria, varying amounts of inacti- 

 vated antiserum and constant amounts of complement or alexin. 

 These mixtures are set away in the thermostat for 3 to 4 hours, are 

 then mixed with agar and plates are poured. The colonies which 

 develop will give an indication of the number of bacteria killed in 

 each mixture when compared with similar plates poured from tubes 

 in which the same original amounts of bacteria had been mixed with 

 alexin alone. The following table will exemplify such a test : 



56 The diagram on page 159, though possibly not expressing with absolute 

 accuracy the idea of sensitization, was devised because it will remove what 

 seem to the writer frequent misconceptions of Bordet's views. Statements are 

 found in the literature which imply (Ehrlich, "Kraus und Levaditi Hand- 

 buch," Vol. 1, p. 8) that Bordet assumes "dass das Komplement direkt an 

 die Zelle angreift," and deny that there is experimental evidence to support 

 this. It is perfectly true that there is no evidence to show such "direktes 



