444 



IMMUNITY. 



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. Pfeiffer's Pheno- 

 menon and its Modifications. Within the last two or 

 three years a number of important 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. 



Pfeiffer found that if cholera organisms were injected 

 into the peritoneal cavity of a guinea-pig highly immunised 

 against the organism, these lost their motility almost im- 

 mediately, gradually became granular and swollen up in 

 places into droplets, and then disappeared in the fluid, all 

 these changes sometimes occurring within half an hour. 

 Further, he found that the same phenomenon was wit- 

 nessed if a minute quantity of anti-cholera serum (that 

 is, the serum of an animal highly immunised against the 

 cholera organism) was added to a certain quantity of 

 cholera microbes, and then injected into the peritoneal 



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

 E. Roux, and Taurelli-Salimbini. 



