MODE OF ACTION OF CYTOLYTIC SERA. 231 



with the alexin, as Ehrlich and Morgenroth believe, or that this 

 union is necessary in order that the alexin may reach the corpuscle. 



It must be admitted that both of these interpretations are purely 

 hypothetical and have been sanctioned by no well-proved fact. We 

 should then find out how far either of these hypotheses conforms 

 with reality by determining how far deductions from them agree 

 with experimental fact. 



Let us consider a fresh hemolytic serum containing both alexin 

 and sensitizer. According to Ehrlich and Morgenroth, this sen- 

 sitizer is combined with alexin if not with all of it, owing to its 

 possible excess, at least with a more or less considerable amount 

 of it. When corpuscles are added the sensitizer unites with them, 

 dragging after it the alexin fixed by its other pole. The amount 

 of alexin that can affect the corpuscles must be only that portion 

 previously fixed by the sensitizer. If there is more alexin in the 

 serum than is necessary to saturate the sensitizer, the excess could 

 have no effect on the corpuscles and would consequently not be 

 utilized. We may therefore conclude that the added corpuscles 

 are unable to modify in the slightest degree the established relations 

 between alexin and sensitizer; they simply fix the sensitizer and are 

 destroyed by the alexin already united with this intermediary 

 body. 



What will happen if we add to such an active hemolytic serum, 

 specific, let us say, for rabbit corpuscles, another sensitizer, say a 

 heated serum affecting hen corpuscles? The result is, as might be an- 

 ticipated, that the mixture obtained destroys hen or rabbit corpuscles 

 indifferently. In accordance with the theory of Ehrlich and Mor- 

 genroth one must consider the two sensitizers as struggling to share 

 the alexin; part of it unites with sensitizer A and the rest with 

 sensitizer B. If we then add the corpuscles affected by sensitizer 

 A, obviously they will absorb it and be injured by the alexin already 

 united to this intermediary body A. But there is no logical reason 

 to suppose that these corpuscles will be attacked by the rest of the 

 alexin united to the other sensitizer that has no combining influ- 

 ence with them. Consequently, on adding subsequently the other 

 species of corpuscles, we should expect them to be destroyed by the 

 remainder of the alexin attached to sensitizer B which is specific 

 for these corpuscles. 



