PROPERTIES OF ANTIBACTERIAL SERUM 477 



it has come into extensive practical use. This observer found that he 

 could intensify the virulence of a streptococcus by growing it alternately 

 in the peritoneal cavity of a guinea-pig and in a mixture of human blood 

 serum and bouillon (vide p. 41). The virulence became so enormously 

 increased by this method, that when only one or two organisms were 

 introduced into the tissues of a rabbit a rapidly fatal septicaemia was 

 produced. Streptococci of this high degree of virulence were used first 

 by subcutaneous, afterwards by intravenous injection, to develop a high 

 degree of resistance in the horse. Injections were continued over a con- 

 siderable period of time, and the protective power of the serum was 

 tested by mixing it with a certain dose of the virulent organisms, and 

 then injecting into a rabbit. The serum of a horse highly immunised in 

 this way constitutes the anti-streptococcic serum which has been 

 extensively used with success in many cases of streptococcic invasion in 

 the human subject. Marmorek, however, found that this serum had 

 little antitoxic power, that is, could only protect from a comparatively 

 small dose of toxin obtained by filtration of cultures. 



Anti-typhoid, anti-cholera, 1 anti-pneumococcic, anti-plague, 

 and other sera are all prepared in an analogous manner. 



Properties of Antibacterial Serum. We have here to 

 consider the three main actions mentioned above, viz. (a) 

 bactericidal and lysogenic action, (6) opsonic action, and (c) 

 agglutinative action. 



(a) Bactericidal and Lysogenic Action. Pfeiffer found that 

 if certain organisms, e.g. the cholera spirillum, were injected 

 into the peritoneal cavity of a guinea-pig highly immunised 

 against these organisms they lost their motility almost immedi- 

 ately, gradually became granular, swollen, and then disappeared 

 in the fluid these changes constitute " PfeifFer's phenomenon." 

 Further, he found that the same phenomenon was witnessed if 

 a minute quantity of the anti-serum was added to a certain 

 quantity of the corresponding organisms, and the mixture 

 injected into the peritoneal cavity of a non-treated animal. 

 Pfeiffer found that the serum of convalescent cholera patients 

 gave the same reaction as that of immunised animals. He 

 obtained the same reaction also in the case of the typhoid 

 bacillus and other organisms. From his observations he con- 

 cluded that the reaction was specific, and could be used as a 

 means of distinguishing organisms which resemble one another. 

 He accordingly considered that a specific substance was developed 

 in the process of immunisation and that this was rendered 

 actively bactericidal by the aid of the living cells of the body. 

 It was subsequently shown, however, by Metchnikoff and by 

 Bordet that lysogenesis might occur outside the body by the 



1 A true antitoxic cholera serum has been prepared by Metchnikoff, E. 

 Roux, and Taurelli-Salimbeni. 



