n6 Immunity 



habituated or tolerant to a certain quantity of mercury or ar- 

 senic, and to certain alkaloids, such as morphin, caffein, nico- 

 tin, cocain, etc., but he does not react as to antigens and no 

 antibodies are formed. To these various substances he 

 acquires only a slight degree of tolerance; to the injurious 

 effects of 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 consumed small quantities of poisons become ir- 

 responsive to their action, and it is well known that Mithrid- 

 ates adopted this mode of defending himself from his enemies. 



Chauveau* believed that the immunity conferred by in- 

 oculations of bacteria was due to the presence of their soluble 

 products, but the first direct demonstration was given by 

 Salmon and Smith,! 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 60 C., and containing no living organisms. CharrinJ 

 found it possible to immunize rabbits against Bacillus pyo- 

 cyaneus by injecting them with the filtered products of cul- 

 tures of that organism, and Bonome similarly to immunize 

 animals against Bacillus proteus, B. cholera gallinarum and 

 the pneumococcus. Roux and Chamberland|| and Roux** 

 were able by the use of boiled cultures of the bacilli of malig- 

 nant edema, and of quarter evil, similarly to immunize 

 animals against these respective infections. 



The subject was much further elaborated by Roux and 

 Yersinff in their experiments with diphtheria toxin, by 

 Behringit in his early studies of diphtheria, and by Kita- 

 sato in his experiments with tetanus. 



These early experiments opened a wide field, through the 

 investigation 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 



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



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



t"Compte rendu," cv, p. 756. 



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



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

 ** Ibid., 1888, 2. ft Ibid., n, 1888, p. 629. 



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

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



