SERUM THERAPY 499 



the cure of human cholera, for Metchnikoff and Klemperer have shown that 

 the serum of persons who have never suffered from cholera is sometimes 

 prophylactic, that the prophylactic property of the blood may be very highly 

 developed in the blood of persons who have just died of cholera, and that it 

 is on the other hand often absent in persons convalescent from the disease 

 (Metchnikoff). 



I. Antibacterial serum. Pfeiffer vaccinated guinea-pigs with cholera 

 vibrios (p. 498) and obtained a serum active in -^ mg. that is to say a serum 

 of which T \ mg. was sufficient to vaccinate a guinea-pig against choleraic 

 peritonitis if injected either before, or at the same time as, or within 

 5 minutes of the vibrios. The serum is bactericidal and agglutinates the 

 cholera vibrio (vide infra). 



Metchnikoff has shown that Pfeiffer's serum has no antitoxic properties : 

 it is very efficient in protecting the blood and organs against infection because 

 it stimulates phagocytosis and allows the leucocytes to ingest the organisms, 

 but it is absolutely useless against intestinal cholera which is an intoxication. 



Reaction of immunity. Pfeiffer has suggested using the immunizing pro- 

 perty of the serum of vaccinated animals as a means of differentiating the 

 cholera vibrio from allied species : according to Pfeiffer, the serum of an 

 animal vaccinated against cholera protects guinea-pigs against infection with 

 the cholera vibrio but not against closely related organisms. To determine 

 the nature of a vibrio then it is sufficient to inoculate the organism under 

 investigation into a guinea-pig treated with anticholera serum : it is said 

 that the animal will only resist infection when the vibrio inoculated belongs 

 to the choleragenic group. 1 Metchnikoff has shown that this test is of but 

 little value : the reaction of immunity may fail in the case of vibrios isolated 

 from the stools of cholera patients and be present in the case of saprophytic 

 vibrios. 



II. Metchnikoff, Roux and Taurelli-Salimbeni's serum. The serum of 

 horses immunized with toxin according to the directions of these observers 

 (vide ante} is bactericidal and agglutinating : it is also prophylactic against 

 choleraic peritonitis in guinea-pigs, the prophylactic dose lying between 0*01 

 and O'OOS c.c. It is antitoxic and protects against intestinal cholera. 



This serum, if inoculated sub-cutaneously into small rabbits in doses of 

 48 c.c. before feeding them with cholera vibrios, will protect them against 

 intestinal cholera. Out of 100 rabbits treated with the serum 56 escaped 

 infection while only 16 per cent, of the controls survived. The serum is 

 efficient if administered at the same time as the animals are fed with the 

 virus but it has no effect at all if the animals be fed 24 hours before the 

 administration of the serum. The value of this serum in human cholera 

 has yet to be proved. 



6. Bactericidal properties. Agglutination. 



1. Pfeiffer was the first to demonstrate the bactericidal and agglutinating 

 properties of the serum of immunized animals in vivo. 



Pfeiffer's phenomenon. If an emulsion of cholera vibrios be inoculated 

 into the peritoneal cavity of a guinea-pig immunized against the vibrio, the 

 peritoneal fluid will in a short time 10-30 minutes be found on microscopical 

 examination to contain only non-motile small more or less granular spherical 

 micro-organisms. 



Experiment. Inject into the peritoneal cavity of an immunized guinea-pig 2 c.c. 

 of sterile broth in which one- half of an agar culture of the vibrio to be examined 



1 A control guinea-pig which has not been treated with the cholera serum must of 

 course be inoculated at the same time with the vibrio under investigation. 



