Passive Acquired Immunity 95 



early as 1886, showed that it was possible to immunize 

 pigeons against hog-cholera by means of repeated injection 

 with cultures exposed to 60 C., and containing no living 

 organisms. Charrin* found it possible to immunize rabbits 

 against Bacillus pyocyaneus by injecting them with the 

 filtered products of cultures of that organism, and Bonomef 

 similarly to immunize animals against Bacillus proteus, B. 

 cholera gallinarum and the pneumococcus. Roux and Cham- 

 berland J and Roux were able by the use of boiled cultures 

 of the bacilli of malignant edema, and of quarter evil, simi- 

 larly to immunize animals against these respective infections. 

 These early experiments opened a wide field of investigation, 

 which was subsequently continued by many others until 

 it was found that the dead as well as the living micro- 

 organisms, and the products as well as the dead bacteria of 

 most of the infectious diseases when properly introduced into 

 animals, could occasion increased resisting power. 



The subject was much further elaborated by Roux and 

 Yersin|| in their experiments with diphtheria toxin, by 

 Behring** in his early studies of diphtheria, and by Kita- 

 satoff in his experiments with tetanus. 



(B) Passive Acquired Immunity. Passive immunity is 

 always acquired, never natural. It depends upon defensive 

 factors not originating in the animal protected, but arti- 

 ficially 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 acti- 

 vity of their products overcome, why cannot these factors be 

 removed from that animal and transferred to another? 



The first experiments seem in this direction to have 

 been made by Babes and Lepp,JJ who found that the 

 blood-serum of animals immunized to rabies possessed a 

 defensive power when injected into other animals. Ogata 

 and Jasuhara found that the subcutaneous injection of 



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



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



t " Ann. de 1'Inst. Pasteur," 1887, 12. Ibid., 1888, 2. 



|| " Ann. de 1'Inst. Pasteur," n, 1888, p. 629. 

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

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

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

 "Centralbl. f. Bakt.," etc., ix, p. 25, 1890. 



