IMMUNITY AND SUSCEPTIBILITY. 117 



which they are susceptible, and then injected with a cult- 

 ure of Bacillus prodigiosus, they will recover. 



c. Intoxication. — The phenomena of immunity are pe- 

 culiar neither to infection by bacteria nor to the influence 

 of their toxins, but are common to many forms of intoxi- 

 cation. In consequence, with the advance of knowledge 

 of the specific diseases, the study of the poisonous prod- 

 ucts of bacteria, and the observation that the effects of 

 many organic and some inorganic poisons bring about 

 similar reactions in the organism, have greatly broad- 

 ened the scope of immunity. 



The metabolic products of bacteria were early noticed 

 and, indeed, as early as 1880, Toussaint and Chauveau \ 

 taught that the protective effect resulting from the in- 

 corporation into the body of attenuated disease germs 

 depended upon the fact that such attenuated cultures 

 contained the metabolic products of the bacteria and thus 

 conferred immunity. This opinion was in direct opposi- 

 tion to the view of Pasteur, who held that infection was 

 essential. It was later discovered that although the bac- 

 teria contained in a culture were killed, it might still 

 confer immunity. Salmon and Smith, 2 as early as 1886, 

 found this true in the case of swine plague. 



Still later it was found that even if the dead bodies of 

 the bacteria were removed by filtration, the metabolic 

 products contained in the filtrate might confer immunity, 

 this being shown by Foa and Bonome 3 to be true of 

 cultures of proteus, Charrin of cultures of Pyocyaneus, 

 Roux and Chamberland 4 of malignant edema, Roux 5 of 

 symptomatic anthrax, Gamaleia of the septicemia of 

 pigeons and cholera, and Carl Fraenkel 6 of diphtheria. 



Hueppe 7 is particular to caution us against supposing 

 that immunity depends entirely upon accustoming the 

 individual to the "specific" poisons of the disease germs, 

 pointing out that in 1887 he had produced immunity by 



1 Compte-rendu de la Soc. Biol, de Paris, 1890, 189 1. 



* Centralbl.f. Bakt. u. Parasitenk., ii., No. 18. 



s Zeitschrift fur Hygiene, v., 415. * Annates de V Inst. Pasteur, 1887, 12. 



6 Ibid., 1888, 8. « Ibid., 1888, 2. * Loc. cit. 



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