350 Chapter XII 



itself, but the toxoids (protoxoids and syntoxoids) represent the 

 toxin modified without further aid from the bacillus. The toxoids, 

 though not toxic, retain all their avidity for antitoxin. According to 

 Ehrlich's conception, the molecule of toxin, under the influence of 

 various factors, readily loses its toxic or toxopliore group, capable of 

 poisoning the animal, whilst still retaining its haptophore group, the 

 group that combines with the antitoxin. The toxoids then would 

 represent this haptophore group of the diphtheria toxin. Without 

 being injurious to animals, the toxoids are capable of neutralising 

 the antitoxin and of setting up in the animal the formation of this 

 antibody. In the experiments carried out by the method of Babes 

 and of the Russian authors we have just mentioned, there would be, 

 according to the view held by Ehrlicb and his school, an immuni- 

 sation by the toxoids. 



The toxones, however, are also capable of vaccinating against the 

 toxin and the toxone and of giving rise to the production of a 

 diphtheria antitoxin, active against these two poisons. This is what 

 [368] is affirmed by Madsen^ and by Dreyer^, according to a communication 

 made by the latter to the International Congress of Medicine held 

 at Paris. 



By means of the various methods briefly described above, is 

 obtained a real acquired immunity against the various bacterial 

 and vegetable poisons and the venoms. On the other hand, with 

 the methods of vaccination mentioned in the eighth chapter, which 

 confer a substantial immunity against micro-organisms, we cannot 

 demonstrate, in the vaccinated animals, a resistance against the 

 corresponding toxins greater than in the unvaccinated control 

 animals. The animals, so thoroughly vaccinated against certain 

 micro-organisms that they withstood enormous doses of culture, 

 did not become capable of resisting the minimal lethal dose of 

 the poison. We are led to conclude, therefore, that immunity can 

 only be obtained against certain of the toxins. For this reason we 

 must regard the attempt made by von Behring to obtain a real 

 immunisation against the toxin of cholera as an important forward 

 step. Before von Behring's attempt, various species of animals had 

 been frequently and very substantially vaccinated against the cholera 



^ Compt. rend, du Congres internat. de med. de Paris (Section de bacteriologie 

 et parasitologie), 1901, p. 40. 



2 Compt. rend, du Congres internat. de med, de Paris (Section de bacteriologie 

 et parasitologic), 1901, p. 45 ; Ztschr. f. Hyg., Leipzig, 1901, Bd. xxxvii, S. 250. 



