Acquired immunity against micro-organisms 267 



micro-organism ; the rabbits that received the minimal lethal dose 

 of this toxin, mixed with serum from vaccinated rabbits, died, as 

 did the control animals, from rapid poisoning. It was evident then 

 that this serum, which prevented infection without in any way 

 hindering intoxication, could not be classed in the category of anti- 

 toxic serums. We find ourselves, therefore, in the presence of 

 a new property of the fluids of the body to which we have given 

 the name of protective or anti-infective poicer. We are driven to 

 this conclusion the more as the serum in question was neither 

 bactericidal nor agglutinative. 



This discovery was soon confirmed by R. Pfeiffer 1 for the cholera 

 vibrio. Animals vaccinated against this organism furnished Pfeiffer 

 with a serum which, whilst not at all antitoxic, was distinctly pro- 

 tective when injected into normal guinea-pigs. It protected these 

 animals from a fatal infection by the vibrio and, when injected into 

 the peritoneal cavity, it set up the granular transformation of the 

 cholera vibrios, Pfeifler's phenomenon. Pfeiffer, for this reason, 

 gave to the protective anti-vibrio serum the name of bactericidal 

 serum. As the granular transformation was produced, under the [281] 

 influence of this serum, with cholera vibrios only and never with 

 other species of vibrio, Pfeiifer gave to the active substance in 

 the serum the name of specific cholera-antibody. This substance, 

 according to his theory, was formed in the animal body at the 

 expense of an inactive antibody which became transformed into an 

 active substance under the influence of the peritoneal endothelium. 



The possibility of thus vaccinating susceptible animals by means 

 of the serums of immunised animals, quite apart from any anti- 

 toxic power, was easily confirmed and extended to several other 

 infective diseases. Pfeiffer and Kolle 2 , Funck 3 , Chantemesse and 

 Widal 4 demonstrated it in connection with the experimental disease 

 produced in animals by the typhoid bacillus; Loeffler and Abel 5 for 

 the Bacillus coli, etc. The protective or anti-infective power of the 

 serum and other fluids of immunised animals was soon recognised 

 as a general property. 



1 Zischr.f. Hyg., Leipzig, 1894, Bd. am, S. 268 ; 1894, Bd. xvm, S. 1. 



2 Ztschr. f. Hyg., Leipzig, 1896, Bd. xxi, S. 203 ; Deutsche med. Wchnschr n 

 Leipzig, 1896, SS. 185, 735. 



3 " La serotherapie de la fievre typhoide," Bruxelles, 1896. 



4 Bull. Soc. med. d. hop., Paris, 1893, 27 Janvier. 



3 Centralbl. f. Bakteriol. u. Parasitenk.. Jena, 1896, I* Abt, Bd. xix, 8. 51 ; 

 Festschr. z. 100/aAr. Sttftungsfeier d. med. cliir. Friedr. Wilh. Institutg, 1895. 



