HEMOLYTIC SERA AND THEIR ANTITOXINS. 207 



with hen blood, on injection into a normal rabbit, confers on the 

 serum of the latter an intense hemolytic power for hen corpuscles.* 

 For the sake of completeness we may add that the serum of the 

 normal animal that has received the immune serum has a cellu- 

 licidal property quite as specific as that of the immune serum 

 employed. We demonstrated in 1895 that, when a guinea-pig is 

 injected with an immume serum specific for the vibrio Metchnikovi, 

 its serum acquires a bactericidal property only against the vibrio 

 Metchnikovi and not against such vibrios as the V. choleras. 



How may the destructive effect of a cytolytic serum be detected 

 in the affected cell? What lesion is produced when this cell is 

 acted on by the serum which indicates the destructive effect? It 

 varies naturally with the nature of the cell in question. In vibrios 

 it consists in a granular transformation; in red blood cells, in hemol- 

 ysis. As is well known, the granular metamorphosis of the cholera 

 vibrio was first noted by Pfeiffer in the peritoneal cavity of actively 

 or passively immunized animals. This investigator thought that 

 this modification of the vibrio could be brought about only in the 

 animal body and never in vitro; according to him this transforma- 

 tion is indicative of an essentially vital action, and is distinct from 

 the bactericidal effect of cholera serum in vitro. According to this 

 author there would be two distinct varieties of bactericidal action, 

 the one occurring exclusively in vivo, and indicated by a granular 

 transformation, and the other produced in vitro, similar in effect 

 but less marked and of less significance. If this conception had 

 proved correct the subject would have been excessively complicated. 

 We know now, however, that it does not agree with the facts: 

 Metchnikoff, in a classical experiment that inaugurated the more 

 comprehensive study of these phenomena, was able to obtain the 

 granular transformation of vibrios in vitro by mixing the organisms 

 with cholera serum plus the peritoneal exudate from a normal 

 guinea-pig. We subsequently demonstrated that fresh cholera 

 serum alone is able to produce this metamorphosis, even when quite 

 limpid and free from cells. 



The important point to be emphasized is that the bactericidal 

 action of a fluid or serum on the cholera vibrio is evidenced both in 

 vivo and in vitro by a granular transformation of the organism. The 



" See p. 170. 



