NEUTRALISATION OF ILEMOLYSINS 1 8$ 



and we would expect just the phenomenon actually ob- 

 served. In order to avoid unnecessary changes we may, 

 until future experiments decide the question, employ the 

 hypothesis that the poisonous molecules possess two 

 groups, the one toxophorous and rather labile, the other 

 haptophorous and more stable. 



It is not necessary that the compound poison should 

 exist to a sensible degree. We have, for instance (cf. 

 p. 74), seen that the velocity of coagulation of casein is pro- 

 portional as well to the rennet present as to the concentra- 

 tion of the calcium ions. As has been made probable by 

 Fuld and Spiro, the " antirennet " contained in normal 

 horse-serum acts so that it binds the calcium ions ; before 

 this research, however, it was supposed that the serum 

 neutralised (bound) the rennet. In this case it is possible 

 to destroy the rennet by heating to 60 C. At lower tem- 

 peratures (30 or so) it weakens slowly ; but the calcium 

 ions, we may suppose, remain unaltered. The rennet 

 evidently corresponds to the toxophorous group, the cal- 

 cium ions to the haptophorous group of a toxin, and the 

 serum to the antitoxin. Evidently the binding of the cal- 

 cium ions by the serum will be independent of the quantity 

 of rennet present. Therefore we may say of the combina- 

 tion, rennet-calcium-ions, that its antitoxin binding property 

 remains unchanged, while its toxic (coagulating) property 

 diminishes with time. Such a point of view has obviously 

 a great advantage over that of Ehrlich ; but in favour of 

 the continuous development of the science, it seems rea- 

 sonable to retain for this case the nomenclature of Ehrlich, 

 provided that no far-reaching theoretical developments are 

 based upon it at least until the decomposition of toxins 



