XXI. ALEXIN ABSORPTION AND THE ANTAGONISTIC 

 PROPERTY OF NORMAL SERA* 



By JULES BORDET AND FREDERICK P. GAY. 



The alexin fixation method has been used for many purposes. 

 The method depends on the factf that bacteria or red blood cells 

 when treated with a suitable sensitizer acquire the property of fixing 

 alexin, and of removing it from the surrounding fluid. By this 

 method it was shown seven years ago J that: 



(a) Animals vaccinated against bacteria usually produce specific 

 sensitizers, whatever be the organism employed. 



(6) And, consequently, although many bacteria resist bacterioly- 

 sis by specific immune serum it is not owing to a lack of active 

 substances in the serum, but on account of resistance on the part 

 of the bacteria. 



(c) Fixation of alexin in the presence of immune serum may be 

 used as a means of diagnosing bacteria and is of even more general 

 applicability than is agglutination, for a sensitizing action is 

 often present when agglutination is absent. 



A year later Gengou§ demonstrated that sensitizers appear after 

 immunization with substances other than bacteria and corpuscles; 

 he found that the serum of an animal immunized against an amor- 

 phous albuminous substance (casein, fibrinogen, alien serum, etc.) 

 sensitizes the specific substance in question, and so endows it with 

 the property of absorbing alexin. 



The subsequent applications of this method and the technic 

 employed are too well known to require mention. The results 

 obtained, however, may be considerably affected by certain factors 



* L'absorption de l'alexine et le pouvoir antagoniste des serums normaux. 



Annales de l'Institut Pasteur, XXII, 1908, 625. 



f Bordet, Hemolytic sera, etc., p. 186. 



X Bordet and Gengou, The existence of sensitizers etc., p. 217. 



§ Gengou, On the sensitizers of sera active against albuminous substances, 



p 241. 



398 



