72 PHYSICAL CHEMISTRY IN BIOLOGY. 



the anti-toxins and the complements of the toxophores. According to 

 BORDET the immune bodies act upon the cells in the way that the latter 

 are sensitive toward the complements (sensibilizators). 



ARRHENIUS arid MADSEN oppose EHRLICH'S theory that the combina- 

 tion between toxin and anti-body is of a chemical nature, but claim that 

 their formation 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 53). 



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 form- 

 ula, must always remain free. 1 According to this theory the toxin is a 

 unit poison, as ARRHENIUS 2 recently admits with EHRLICH, that the poison 

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

 stance which has the same ability to combine with antitoxin as the 

 toxin itself. 



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

 a chemical combination between the antigen and the anti-body. Accord- 

 ing to EHRLICH besides this the substrate (or the cells sensitive to the 

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

 theory of ARRHENIUS-MADSEN. 



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 ). On the 



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. 



