156 INFECTION AND RESISTANCE 



As a rule, these experiments have been carried out with normally 

 hemolytic serum and unsensitized cells, though in certain cases 

 Ehrlich has employed sensitized cells; but whenever this was done 

 exposure to complement for purposes of absorption has been for 

 much briefer periods than when normal serum was used. This point 

 is significant when we come to consider the objections to the inter- 

 pretation of the preceding experiment in favor of a plurality of com- 

 plement, objections raised chiefly by Wilde 52 and by Bordet. 



Wilde refuted particularly the experiments of Neisser, who 

 claimed that the absorption of fresh rabbit serum with anthrax 

 bacilli deprived this serum only of its bactericidal but not of its 

 hemolytic complement. Wilde showed that, if a sufficient excess of 

 anthrax bacilli (or in given cases of typhoid bacilli or cholera spir- 

 illa) were added, both bactericidal and hemolytic complement could 

 be absorbed from normal serum. He concludes that there is actually 

 only one alexin present, but that the red cells and anthrax bacilli 

 differ in their susceptibility to this alexin (or, in other words, that 

 the sensitization of these cells by the normal serum is unequal, a 

 conclusion which seems rational in view of the fact, now well known, 

 that one and the same complement may differ greatly in the degree 

 of its activity upon different sensitized complexes. 



Bordet has analyzed the conditions in a similar way. He found 

 that absorption of normal serum with unsensitized cells rarely de- 

 prived this serum of all of its alexin, even when these cells were used 

 in considerable amounts. This he attributed to the feeble sensitiza- 

 tion of the cells. If, however, strongly sensitized cells were added 

 to such a normal serum, all the alexin would be taken up. He refers 

 the phenomenon of specific alexin absorption, observed by previous 

 workers, to insufficiency in the perfection of sensitization on the 

 part of the cells used in the preliminary exposure ; and subsequent 

 work with complement fixation seems to bear him out. 



Most of these arguments, though they seem to us perfectly valid 

 in the light of the experimental facts, have been answered by Ehrlich 

 and his school by the assumption of the existence of so-called "poly- 

 ceptors." Ehrlich now admits that the amboceptors cannot be shown 

 to differ from each other. However, he does not believe that differ- 

 ences in the intensity of sensitization explain variation in the 

 functional efficiency of different complements upon sensitized cell 

 complexes, nor does he accept, for proof of this, the fact that comple- 

 ment may be entirely absorbed out of a serum by a complex, even 

 though the complement may be comparatively inefficient as an acti- 

 vator in the given case. He assumes that the sensitizer or "ambo- 

 ceptor" may possess a number of complementophile groups (poly- 

 ceptors), by means of which a number of different complements may 



52 Wilde. Habilitations Schrifft, Munich, 1901. Also Berl kl. WocJi., 

 No. 34, 1901. 



