INFECTION AND IMMUNITY. 573 



learn the blood serum contains normally a small amount 

 of antitoxic, agglutinative, and bactericidal action against 

 a great variety of pathogenic bacteria. 



To those ill-defined substances whose affinities are 

 restricted to the soluble toxins elaborated by the inva- 

 ding bacteria the name " antitoxins " is now generally 

 applied. Contrary to what we have seen in the case of 

 the " alexins " normally present, antitoxins are to be de- 

 tected in the normal animal organism in very small 

 amounts. When they do exist under such conditions v 

 they are of but comparatively feeble potency. 1 In the 

 great majority of instances antitoxic activities are acquired 

 peculiarities ; acquired in some cases in a more or less nat- 

 ural manner, as in the course of a non-fatal attack of a 

 specific malady ; induced in others by purely artificial 

 means, as we have seen to be possible in the case of diph- 

 theria, tetanus, etc. Our acquaintance with these bodies 

 extends little further than their physiological functions 

 and some of the means that induce their generation. 

 We have no satisfactory knowledge of their intimate 

 nature or of the primary sources of their production. 

 They are believed by some (Buchner 2 and Metchnikoff' 3 ) 

 to represent, when artificially induced, bacterial toxins 

 that have been modified by the vital action of the inte- 

 gral cells of the body ; and Roux 4 and Buchner 5 main- 



1 See Bolton : Transactions of Association of American Physicians, 

 1896, vol. xi. p. 62. Pfeiffer : Deutsche ined. Wochenschrift, 1896, 

 No. 8. Fisehl and v. Wiinschheim: Centralhlatt fur Bakteriologie, 

 Parasitcnkunde, und InfektionskranklH'iten, 1896, Abt. i. Bd. xix. S. 

 (i.">2. Wasscrmann : Berliner klin. Wochenschrift, 1898, No. 1. 



2 Buchner: Munchener med. Wochenschrift, 1893, Nos. 24 and 25. 



'Metschnikoff: Weil's Handlmch der Hygiene, Bd. ix. Lieferung 1, 

 8.48. 



*Roux : Annales de PInstitut Pasteur, 1894. p. 722. 



'Buchner: Berliner klin. Wochenschrift, 1894, No. 4. 



