98 Immunity 



injurious antigens he may acquire an almost unlimited degree of 

 immunity through the formation of the antibodies. 



From remote antiquity it has been known that those who regularly 

 consume small quantities of poisons become irresponsive to their 

 action, and it is well known that Mithridates attempted this mode of 

 defending himself from his enemies. 



Chauveau* believed that the immunity conferred by inoculations 

 of bacteria was due to the presence of their soluble products, but the 

 first direct demonstration of the fact was by Salmon and Smith, f who, 

 as early as 1886, showed that it was possible to immunize pigeons 

 against the hog-cholera bacillus by means of repeated injection 

 with cultures exposed to 6oC., and containing no living organisms. 

 CharrinJ found it possible to immunize rabbits against Bacillus 

 pyocyaneus by injecting them with the filtered products of cultures 

 of that organism, and Bonome similarly to immunize animals 

 against Bacillus proteus, B. cholera gallinarum and the pneu- 

 mococcus. Roux and Chamberland|| and Roux** were able by the 

 use of boiled cultures of the bacilli of malignant edema, and of 

 quarter evil, similarly to immunize animals against these respective 

 infections. 



The subject was much further elaborated by Roux and Yersmff 

 in their experiments with diphtheria toxin; by BehringJJ in his 

 early studies of diphtheria, and by Kitasato in his experiments 

 with tetanus. 



These early experiments opened a wide field, through the investiga- 

 tion of which we now know that the products as well as the living or 

 dead bacteria of most of the infectious diseases, when properly 

 introduced into animals, can induce immunity. 



(B) Passive Acquired Immunity. Passive immunity is always 

 acquired, never natural. It depends upon defensive factors not 

 originating in the animal protected, but artificially or experimentally 

 supplied to it. The fundamental principle is simple and has become 

 the basis of serum therapeutics. If the immunized animal generates 

 factors by which the infecting bacteria can be destroyed or the 

 activity of their products overcome in its body, cannot these factors 

 be removed and the benefit they confer transferred to another 

 animal ? 



The first experiments in this direction seem to have been made 

 by Babes and Lepp,|||| who found that the blood-serum of animals 



*"Ann. de 1'Inst. Pasteur," 1888, 2. 



t"Centralbl. f. Bakt.," etc., 1887, n, No. 18, p. 543. 



J "Compte rendu," de la Soc. de Biol., cv, p. 756. 



"Zeitschrift f. Hyg.," v, p. 415. 



j| "Ann. de 1'Inst. Pasteur," 1887, 12. 

 >*Ibid., 1888, 2. 

 ft Ibid., 1888, n, p. 269. 

 "| "Deutsche med. Wochenschrift," 1890, No. 50. 



" "Zeitschrift fur Hygiene," 1891, x, p. 267. 

 "Annales de 1'Inst. Pasteur," 1889, vol. in. 



