MODE OF ACTION OF CYTOLYTIC SERA. 235 



tizer would seem to affect a corpuscle differently, according to the 

 alexin used. In different instances the sensitizer may be the same, 

 but the dose would vary with the alexin employed. 



From this easily explicable fact, that the amount of sensitizer 

 necessary varies with the alexin employed, Ehrlich and Morgenroth 

 feel justified in concluding that the serum contains several sen- 

 sitizers, all of which affect rabbit corpuscles, but which differ from 

 one another. One of these sensitizers renders the corpuscle suscep- 

 tible to guinea-pig alexin, and another to rabbit alexin. This com- 

 plicates unnecessarily the already sufficiently complicated question 

 of hemolytic sera.* 



II. On the Unity of the Alexin in a Given Serum. 



We know that the alexins from different animal species are not 

 identical. But does a given alexic serum, say from the guinea-pig, 

 contain a single alexin or several of them that differ in chemical 

 constitution? It is rather difficult to reply to the question put in 

 this way, as our knowledge of the chemical nature of the alexin 

 is practically nil. We may question, however, whether the alexin is 

 functionally simple, that is to say, whether the alexin (or alexins, 

 if there are several) can attack various cells such as corpuscles and 

 bacteria indifferently, particularly when these cells are sensitized. 

 In this form the question is of lively interest in studies on immunity 

 and may be more easily answered. 



We know that Buchner in his first studies on the alexins of normal 

 sera,f that have by now become classical, considered the substance 

 that destroys bacteria as identical with the one that produces 

 hemolysis. We offered facts a year ago that seemed to corroborate 

 this opinion. 



We have just recalled these facts in the preceding article! When 

 a serum is deprived of its alexin by the addition of a sensitized 

 bacterium or corpuscle, the fluid becomes incapable of destroying 

 another sensitized cell, even when it is different from the one that 

 has taken up the alexin in the first place. It must then be always 



* By the same process of reasoning Ehrlich and Morgenroth think that in a 

 given normal serum there are several intermediary bodies (sensitizers), all active 

 against the same corpuscles, but each requiring a different alexin. 



t See, for example, Verhandlungen der Congresses fur innere Medicin, 1892. 



