THEORIES OF IMMUNITY. 



the International Congress of that year that Behr- 

 ing attempted to argue that antitoxine forma- 

 tion occurred in all forms of acquired immunity, 

 and that bacteria introduced into the bodies of 

 animals containing this principle were incapable 

 of producing any hurtful results. 



Taking up this point, Metchnikoff undertook 

 to investigate the acquired immunity occurring 

 in pneumo-enteritis of hogs (hog-cholera?). 

 He demonstrated (Ann. de l'lnst. Pasteur, 1892, 

 T. "VI., p. 289 ) that the resistance of the animal 

 to the bacterium in this case does not depend 

 upon the formation of an antitoxine — which is 

 entirely wanting in this form of acquired im- 

 munity. (He demonstrated this in the paper 

 spoken of, as follows : he first tested the serum of 

 animals immunized to pneumo-enteritis, and 

 found that it made a favorable medium for the 

 cultivation of the bacillus; there was, therefore, 

 no bactericidal action in the serum. He injected 

 mixtures of the serum of animals dead of pneu- 

 mo-enteritis (hog-cholera?) with the serum of 

 immune animals and with the serum of non- 

 immune animals, and in both cases found that 



26 



