228 INFECTION AND IMMUNITY 



occurred; yet, centrifugalized at this temperature, immune body was 

 found to have become bound to the corpuscles, the complement re- 

 maining free in the supernatant fluid. If the same mixture, however, 

 was exposed to 37 C., hemolysis promptly occurred. 



From this, Ehrlich concluded that complement did not directly 

 combine with the corpuscles, but did so through the intervention of 

 the immune body. This immune body, he reasoned, possessed two dis- 

 tinct atom-groups or haptophores; one, the cytophile haptophore group, 

 with strong affinity for the red blood cell; the other, or complemento- 

 phile haptophore group, with weaker avidity for the complement. Be- 

 cause of this double combining power, Ehrlich speaks of the immune 

 body as "amboceptor." These views are graphically represented in 

 Figs. 57 and 58. 



Thus, according to Ehrlich and his pupils the alexin, or comple- 

 ment, acts upon the antigen indirectly only through the "zwischen- 

 koerper" or "amboceptor." Bordet 1 claims, however, and in our 

 opinion rightly so, that this conception is not justified by observed facts. 

 The only thing that we actually know is that alexin or complement 

 does not go into union with the unsensitized antigen, but that the ac- 

 tivity of the alexin upon the antigen is made possible only by prelim- 

 inary sensitization or by union with the specific antibody. The specific 

 antibody sensitizes to the action of the complement but is not neces- 

 sarily a sort or bridge with an antigenophile group and a complemento- 

 phile group. The difference is a fundamental one, and it would seem 

 to us that Bordet's view is more conservative. For this reason it seems 

 better to refer to the substances involved, alexin or complement, as 

 sensitizer instead of amboceptor, since sensitizer expresses only exactly 

 what happens, whereas amboceptor implies a theory, that is, inter- 

 mediation of this substance between complement and antigen. 



AGGLUTININS 



Although Metchnikoff 2 and Charrin and Roger 3 had noticed pecul- 

 iarities in the growth of bacteria when cultivated in immune sera, which 

 were unquestionably due to agglutination, the first recognition of the 

 agglutination reaction as a separate function of immune sera was the 

 achievement of Gruber and Durham. While investigating the Pfeiffer 

 reaction with B. coli and the cholera vibrio, Gruber and Durham 4 



1 Bordet, A Resume of Immunity in "Studies in Immunity." Transl. by Gay, 

 Wiley & Son, 1909. 2 Metchnikoff, "Etudes sur 1'immuniteV' IV Memoir, 1891. 



3 Charrin et Roger, Compt. rend, de la soc. de biol., 1889. 



4 Gruber und Durham^ Munch, med. Woch., 1896. 



