480 IMMUNITY. 



injected along with them. Here again is presented the 

 remarkable potency of the antagonising substances in the 

 serum, which in this case lead to the destruction of the 

 corresponding microbe. 



The anti-streptococric serum of Marmorek may be briefly 

 described, as 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. 53). 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. Strepto- 

 cocci 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 considerable 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 toxine 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 Antimicrobic Serum. Within the last 

 two or three years important objective reactions presented 

 by antimicrobic serum against the corresponding organism 

 have been discovered, and these are of high importance, as 

 they afford valuable aid in the study of the nature of the 

 preventive power. Of such actions the two chief are the 

 lysogenic and the agglutinative. 



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

 Roux, and Taurelli-Salimbini. 



