HEMOLYTIC SERA AND THEIR ANTITOXINS. 213 



tive form, as it is stored up against possible necessity in the body. 

 In this latter form the antibody is incapable of destroying vibrios. 

 To be sure, Pfeiffer does not deny that a granular transformation 

 may occur in vitro with fresh cholera serum, but he thinks this 

 effect is due to a small amount of the ferment substance in the 

 serum that renders the antibody bactericidal. It is evident that 

 Pfeiffer has been obliged to agree essentially with our point of 

 view in order to explain bacteriolysis in vitro, at least to the extent 

 of admitting that two substances are necessary. The resemblance 

 between the two theories, however, is only superficial. 



According to Pfeiffer and his pupils the substance present in 

 fresh normal serum, that has been named alexin, would not be in the 

 strict sense a bactericidal substance, but rather the ferment which 

 transforms the inactive antibody into its active form. The trans- 

 formation of vibrios in vitro by fresh cholera serum would be due to 

 the effect of the active antibody and not to a direct action of the 

 alexin, the one function of which is to produce the active antibody. 

 Consequently the real cellulicidal substance would always be specific ; 

 instead of being the same in various immune sera, as we think of 

 it, it would vary in each one, since the antibodies in immune sera 

 are essentially different. 



But if the alexin bears no direct causal relation to alterations 

 shown by vibrios and corpuscles, why do normal sera, which have 

 no specific antibodies, show a distinct if inferior bactericidal effect 

 on vibrios? How, as Buchner has emphasized in his valuable 

 researches,* can these normal sera produce a certain amount of 

 hemolysis? 



This hemolysis, by normal serum, although less, is nevertheless 

 quite comparable to that produced by hemolytic sera. Artificial 

 immunization, as indicated by the production of specific antibodies, 

 does not produce cytolytic power, but renders it specifically more 

 intense by forming a sensitizer or specific antibody. All this tends 

 to invalidate Pfeiffer's theory. 



This theory, to be sure, would seem more reasonable if cytolytic 

 phenomena in vitro were much less intense than those in the animal 

 body (peritoneal cavity). There is, however, no difference in inten- 



* Buchner, as we know, brought out the fundamental fact that normal serum 

 heated to 55 degrees loses both its bactericidal and globulicidal properties. 



