478 IMMUNITY. 



may afterwards be partially restored, thereby indicating that 

 there has been an actual regeneration of antitoxine though 

 no fresh toxine has been injected. These facts disprove 

 the theory held by some that the antitoxine is a modified 

 toxine a theory which, besides, is scarcely intelligible on 

 biological grounds. According to Ehrlich's theory, the cells 

 of the organism have acquired under the stimulus of the 

 toxine a secretory or regenerating habit which lasts for some 

 time after the stimulus has been removed. It may further 

 be mentioned that after the antitoxic property has dis- 

 appeared from the blood the animal still possesses a degree 

 of immunity to the toxine. Whether or not this is due to 

 the fact that there are still surplus antitoxine molecules in 

 the cells, but not in such excess that they pass into the 

 blood, we cannot definitely say. 



Of the chemical nature of antitoxines we know little. 

 From their experiments C. J. Martin and Cherry deduce 

 that while toxines are probably of the nature of albumoses, 

 the antitoxines probably have a molecule of greater size, and 

 may be allied to the globulines. Such a supposed difference 

 in the sizes of the molecules might explain the following 

 facts, observed by Fraser and also by C. J. Martin. If a 

 certain amount of toxine be injected subcutaneously, and at 

 the same time an amount of antitoxine sufficient to neutralise 

 it in vitro be injected intravenously, the latter will nearly 

 neutralise the former. If, however, the antitoxine also be 

 introduced subcutaneously (into a different part of the 

 body), from ten to twenty times as much is required to 

 effect neutralisation. The explanation of this would be 

 that the large molecule of the antitoxine was absorbed 

 relatively more slowly than that of the toxine ; thus in a 

 given time there was more of the latter free in the circula- 

 tion and ready to produce pathogenic effects. In the case 

 of the intravenous injection of antitoxine, the toxine on 

 reaching the blood stream was neutralised by the antitoxine 

 already circulating there. 



Antitoxine, when present in the serum, leaves the body 

 by the various secretions, and in these it has been found, 



