INTERREACTIONS OF TOXIN AND ANTITOXIN 87 



as an inert one of no further interest ; and this theory of dissocia- 

 tion is open to the objection urged by Nernst, and probably felt 

 by most bacteriologists on the first enunciation of the views of 

 Arrhenius and Madsen. Thus, if the combination of toxin and 

 antitoxin undergoes dissociation in the living animal and the toxin 

 is set free, it will immediately combine with the susceptible cells. 

 The equilibrium will now be disturbed and more toxin-antitoxin 

 molecules will be dissociated, more toxin set free, and more cells 

 poisoned ; and this process will go on until all the toxin has been 

 passed on to the cells and the antitoxin left free. Now this 

 dissociation takes place quickly, so that on this theory it would 

 seem that the antitoxin would only interpose a very temporary 

 barrier between the cells and the toxin, the lethal action of which 

 would be delayed, but in no way inhibited. We will return to 

 this question of dissociation shortly, and meanwhile state briefly 

 Ehrlich's objections to the physical-chemical theory. In the first 

 place, he points out that if we make a mixture of two alkaloids, 

 of which one is haemolytic and the other not, and neutralize them 

 by the addition of a strong acid, the result may be represented by 

 a hyperbolic curve ; this is put forward as a parallel experiment 

 to the neutralization by antitoxin of a substance containing active 

 toxin and inert toxoid. Secondly, some of the curves given by 

 Madsen and Arrhenius do not correspond very closely with the 

 observed results, and this is especially the case at their commence- 

 ment and termination. At the commencement of the curve it is 

 found in many cases that the addition of small amounts of anti- 

 toxin does not influence the toxicity ; this is readily explained on 

 the supposition of the existence of prototoxoid, but hardly on any 

 other hypothesis. The most interesting point, however, is the 

 behaviour of the curves at the termination i.e., in what Erhlich 

 would call the region of the toxons ; here Arrhenius and Madsen 

 usually found figures which were lower than the calculated results. 

 Now Ehrlich holds that traces of toxin do not lead to paralysis, 

 and if the effect of a nearly neutral mixture of toxin and antitoxin 

 were due to dissociation we should expect no paralysis to occur, 

 the toxic action being due to toxin, and not, as Ehrlich thinks, to 

 toxon. Madsen and Arrhenius suggest that the action of this 

 trace of antitoxin may be modified by the presence of antitoxin in 

 excess. Further, Madsen and Dreyer claim to have found a 

 diphtheria poison, of which small quantities would cause paralysis 

 without the addition of antitoxin, so that the question of toxon 



