ACQUIRED IMMUNITY 73 



be produced by introducing into the animal body such chemical 

 products (results of bacterial growth in culture fluids) that have been 

 produced in the laboratory. 41 



Similar attempts to immunize rabbits against certain forms of 

 septicemia by the injection of culture filtrates were made by Cham- 

 berland and Roux 42 in 1888, 43 and the same investigators applied 

 this method to anthrax immunization just prior to the discovery of 

 diphtheria toxin by Roux. However, neither in hog 44 cholera 45 

 nor in the other infections upon which this method was first tried do 

 the bacteria produce a true soluble toxin, and the immunization 

 which was accomplished depended probably upon the injection of 

 bacterial extracts. Nevertheless, these attempts had shown the way 

 in a new direction, and bore immediate fruit in the investigations of 

 Brieger and Fraenkel, 46 and more especially in those of Beh- 

 ring 47 48 49 and his collaborators. Fraenkel, though following the 

 method of injecting filtered diphtheria culture fluids, came to the 

 erroneous conclusion that the toxin and the immunizing substances in 

 the cultures were not identical (loc. cit., p. 1135). 50 The degree of 

 immunity obtained in his experiments, moreover, was a slight one 

 only. 



Behring, in his first work, in collaboration with Kitasato, suc- 

 ceeded in immunizing animals with culture filtrates and with pleural 

 exudates of diphtheritic animals. Similar results were accomplished 

 with tetanus. Since the publication of these results especially in 

 consequence of the epoch-making discovery of passive immunization, 

 to which they were the immediate guides, toxin immunization has 

 been investigated and accomplished in all cases in which a true solu- 

 ble toxin can be demonstrated. It has accordingly been carried 

 out with the exotoxins of pyocyaneus 51 bacilli, the bacilli of 

 symptomatic anthrax 52 and botulinus, 53 the specific leukocidins 54 



41 For a copy of the original paper 'iy Salmon and Smith I am indebted 

 to Professor Theobald Smith. 



42 Chamberland and Roux. Ann. Past., Vol. 1, 1888. 



43 Op. Cit., Vol. 2, 1889. 



44 Joest in "Kolle u. Wassermann ^andbuch, etc.," Vol. 3, p. 632. 



45 Karlinski. Zeitschr. f. Hyg., Vol. 28, 1898. 



46 Brieger and Fraenkel. Berl. kl. Woch., 1890, Nos. 11, 12 and 49. 



47 Behring and Kitasato. Deutsche med. Woch., No. 49, 1890. 



48 Behring. Deutsche med. Woch., No. 50, 1890. 



49 Behring and Wernicke. Zeitschr. f. Hyg., 1892. 



50 De Schweinitz, indeed, who further studied hog cholera immunization 

 (Medic. News, 1892; Centralbl. f. Bakt., Vol. 20, 1896), claimed that in 

 sterilized milk the bacillus produced "enzymes" with which immunization 

 could be accomplished. 



51 Wassermann. Zeitschr. f. Hyq., Vol. 22. 

 52 Kempner. Zeitschr. f. Hyg., Vol. 23, 1897. 



53 Grassberger and Shattenfroh. Deuticke, Wien, 1904. 



54 Denys and Van der Velde. "La Cellule," Vol. 2, 1895. 



