Artificial immunity against toxins 379 



refractory condition. According to von Behring the great difference 

 in the duration of the isopathic and antitoxic immunities is only an 

 apparent one. It is due to the fact that antitoxins are usually 

 introduced along with the serum of different species which sets up 

 a strong reaction and is rapidly eliminated from the animal. Thus 

 the antitoxic serum of the horse is usually injected into small 

 animals such as guinea-pigs, rabbits, and mice. When, however, 

 von Behring injected horses with antitoxic serums from other horses, [398] 

 the antitoxic immunity lasted almost as long as in animals vaccinated 

 with toxins. Ransom^ has developed this thesis in a work carried out 

 in von Behring's Institute at Marburg, and supports it by compara- 

 tive researches which demonstrate the more rapid disappearance of 

 the antitoxin when introduced with the serum of a different species 

 than when introduced with that of the same species. 



Even should we accept the current view on the greater duration 

 of the antitoxic power of the blood in isopathic immunity, the hypo- 

 thesis of the transformation of toxin by the cells of the animal is 

 not necessarily invalidated. If a part of the toxin introduced into 

 the animal remains stored for some time in an organ it is evident 

 that only gradually can it be subjected to the transforming action 

 of the cells. It is impossible, in the present state of our knowledge, 

 to demonstrate this proposition, but we may invoke in its favour the 

 prolonged persistence of red blood corpuscles when introduced into 

 the body of a different species of animal (see Chapter IV). These 

 corpuscles are in the end always completely digested but the process 

 is of long duration. 



The same hypothesis will also explain a fact, first demonstrated 

 by Roux and Vaillardl They have shown that after repeated bleed- 

 ings of rabbits immunised against tetanus, the antitoxic property 

 of the blood was soon raised to almost the same value as before. 

 Salomonsen and ^ladsen^ have confirmed the fact of the regene- 

 ration of antitoxin after the bleeding of their animals (horses and 

 goats) immunised against diphtheria. Those authors who do not 

 accept the possibility of the transformation of toxins in the production 

 of antitoxins, regard these facts as absolutely incompatible with the 

 hypothesis which they attack. Thus, Weigert* considers that the 



1 Journ. Path, and Bacteriol, Edin. and London, 1900, Vol vi, p. 180. 



2 Ann. de I'lnst. Pasteur, Paris, 1893, t. vii, p. 82. 



3 Ann. de VInst. Pasteur, Paris, 1898, t. xii, p. 763. 



4 Op. cit. supra, p. 363, iv Jahrg., S. 122. 



