68 . GENERAL AND PHYSICO-CHEMICAL. 



ARRHENIUS opposes EHRLICH'S theory that the combination between 

 toxin and anti-body is of a chemical nature, but claims, that their for- 

 mation does not proceed until one of the components has been used up. 

 An equilibrium is established between the free toxin and the free anti- 

 body on one side and the combination of the two on the other, which 

 the law of mass action requires according to the formula: 



C . C = K . C N (page 32). 



toxin anti-body toxin +anti-body 



For tetanolysin (a substance obtained from tetanus cultures, which dissolves 

 red-blood corpuscles) and its anti-body, as well as for diphtheria toxin and the 

 corresponding anti-body, n=2 was found, i.e., in the combination of a molecule 

 of toxin with a molecule anti-body two molecules toxin-antitoxin combination 

 was formed. 



The toxic action which a mixture of toxin and anti-body exerts 

 depends upon the quantity of toxin which, according to the above 

 formula, must always remain free. 1 According to this theory the toxin 

 is a unit poison, as ARRHENIUS 2 now admits with EHRLICH, that the 

 poison is gradually transformed into a non-toxic or only slightly toxic 

 substance whichjhas the same ability to combine with antitoxin as the 

 toxin itself. 



EHRLICH'S theory, as well as that of ARRHENIUS admits of a chem- 

 ical combination between the antigen and the anti-body. According 

 to EHRLICH besides this the substrate (or the cells sensitive to the anti- 

 gen) combines with the antigen, which is not conformable with the theory 

 of ARRHENIUS. 



The combination toxin-anti-body is first gradually produced, and 

 then it is taken up from all sides so that the toxin is fastened to the 

 anti-body by a secondary process (exception, cobra poison). The com- 

 bination toxin-antitoxin is not reversible in the ordinary sense. This 

 is most easily shown by the fact that to- a certain limit more toxin is 

 neutralized according to the time allowed to elapse before the quantity 

 of toxin remaining free is determined by injection into an animal or in 

 other ways. 3 In certain cases it is possible to obtain the toxin again in 

 an active form from the toxin-antitoxin combination, and indeed by 

 treatment with very dilute hydrochloric acid (MORGENROTH 4 ) . See 

 also page 64 on the setting free of rennin from its combination with 

 normal serum and with egg-white. HEDiN 5 has also been able to obtain 



1 Zeitschr. f. physik. Chem., 44, 7 (1903). 



2 Immunochemie, Leipzig, 1907, 132. 



3 Martin and Cherry, Proc. Roy. Soc., 1898, 420. 



4 ]Berl. klin. Wochenschr., 1905, No. 5; Festschr. z. Eroffnung d. pathol. Instit. 

 Berlin, 1906; Virchow's Arch., 190, 371 (1907). 

 6 Zeitschr. f. physiol. Chem., 77, 229 (1912). 



