Artificial immunity against toxins 343 



To Pliny we are indebted for the now well-known story, that 

 Mithridates of Pontus possessed the means of protecting himself 

 against various poisons by a process of adaptation, and, amongst [360] 

 others, by the use of the blood of Pontine ducks to which he had 

 given poisons by the mouth. 



The adaptation of horses and of the highlanders of Styria to arsenic, 

 as well as that of the many morphinomaniacs to morphia, is known 

 to everybody. A man, habituated to morphia, is able to consume 

 daily a dose several times the fatal one ; indeed, cases have been 

 known of people acquiring the power of consuming two, and even 

 three, grammes of morphia per diem. Man may acquire an adapta- 

 tion to toxic substances of the most diverse character, such as 

 arsenic, alcohol, morphia, nicotine, etc. 



Even when we had obtained much information concerning acquired 

 immunity against micro-organisms we still knew nothing of the 

 mechanism of such adaptation, or as to the possibility of acquiring a 

 special immunity against bacterial poisons. Charrin and Gamaleia's 

 discovery that animals vaccinated against a micro-organism are just 

 as susceptible to its toxic products as normal animals, led Bouchard \ 

 in whose laboratory it was made, to say that the idea of the adapta- 

 tion of cells to bacterial poisons must be dropped. He developed 

 this thesis at the International Congress at Berlin in 1890, and 

 formulated it as follows : " When we inject a healthy animal and 

 a vaccinated one with the soluble products of the micro-organism 

 which has been used for the vaccination, the dose required to kill 

 each animal is exactly the same. Let us not speak, then, of the 

 training of the leucocytes, and of the adaptation of the nerve cells 

 to bacterial poisons : it is pure rhetoric." At this time we had only 

 just commenced to acquire exact knowledge concerning the toxins 

 of micro-organisms. For a considerable period they were sought 

 for amongst the ptomains, very stable substances allied to the 

 alkaloids ; here, however, we were working in a wrong direction. It was 

 not until the classic researches of Roux and Yersin^ on diphtheria 

 toxin, published in 1888 and 1889, that the true nature of bacterial 

 poisons was revealed. It was found that we were not dealing with 

 ptomains, but with soluble ferments, substances of indeterminate 

 chemical composition, allied to the albuminoids, and, like them, 



1 "Essai d'une theorie de rinfection," Berlin, 1890 j "Les microbes pathog^nes," 

 Paris 1892 t) 33 



2 Ann. de Vlnst. Pasteur, Paris, 1888, t. n, p. 629 ; 1899, t. in, p. 273. 



