Ii8 PATHOGENIC BACTERIA. 



the use of entirely attenuated bacteria that were purely 

 saprophytic. His results were also confirmed by Chau- 

 veau in 1889. 



The success of Behring 1 and Roux 2 in immunizing 

 animals to the toxins of diphtheria and tetanus is well 

 known, and close upon their researches with these toxins 

 came Calmette's 3 studies of serpents' venom, which 

 showed that gradual progressive intoxication produced 

 immunity, and Ehrlich's 4 experiments with ricin and 

 abrin and the production of immunity to these alkaloids. 

 Still later Wassermann produced immunity to poisonous 

 eel's blood, and Klemperer and Scheplewski to the 

 " Botulism us-gift " (meat-poison). Immunity to a min- 

 eral poison is seen among the arsenic eaters, and Bes- 

 redka 5 has recently found it possible to produce immu- 

 nity to arsenic in rabbits, accompanied by the occurrence 

 of an antitoxic substance (antiarsenine) in the blood. 



The immunity thus induced is active and probably 

 cytogenic, and does not seem to differ perceptibly from 

 that produced by the bacteria themselves. 



It is interesting to observe that the activity of the fil- 

 tered culture depends upon the solubility of the metabolic 

 products, and that in cases where these are with difficulty 

 extracted from the germs the filtrates are very feebly active. 



Passive Immunity. — Passive immunities, not depend- 

 ing upon the activity of the organism, can be developed 

 experimentally. 



d. Antitoxins, derived from immunized animals, confer 

 a perfect immunity upon the animal into whose blood 

 they are introduced. As this subject is one of great im- 

 portance to which much space must be devoted, it will 

 be discussed in a subsequent part of the chapter. 



e. Tissue suspensions sometimes produce a protective 

 reaction upon toxins when introduced into the body 



1 Zeitschrift filr Hygiene, 1892, xii., I. 



2 Annales de V Inst. Pasteur, 1888, ii., p. 629; 1898, p. 640 

 s Ibid., 1894, viii., p. 275. 



4 Deutsche med. Wochenschrift, 1891, Nos. 32 and 44. 



5 Ann. de V Inst. Pasteur, June, 1899, p. 30. 



