2l6 LECTURES ON IMMUNITY 



power. Biltz finds that on adding increasing quantities of 

 arsenious acid to a given quantity (200 c.c.) of water in 

 which are suspended 10 c.c. of the hydrate, the quantity 

 absorbed increases much more slowly than the concentra- 

 tion of the liquid. The increase of the arsenious acid ab- 

 sorbed by the hydrate is only proportional to the fifth root 

 of the concentration of the liquid. This observation is in 

 good concordance with other experiments on analogous 

 subjects (for absorption by means of charcoal Schmidt 

 found the fourth root, which seems to be the most general 

 case in so-called adsorption processes). 



Biltz finds that there is a very close analogy between 

 this phenomenon and the neutralisation of toxins by means 

 of antitoxins. It is very astonishing that Biltz has not 

 tested his idea on a practical example, for instance on the 

 observations regarding the neutralisation of tetanolysin or 

 diphtheria-toxin published at that time. If I have under- 

 stood Biltz aright, the toxin would be analogous to the 

 arsenious acid in true solution and the antitoxin would be 

 in the colloidal state and correspond to the ferric hydrate. 



From this point of view I have examined the observed 

 figures cited above regarding diphtheria-poison, tetanolysin 

 with antilysin or cholesterin, and saponin with cholesterin 

 or ox-serum. In the two first cases, where the reaction- 

 products enter into the equation of equilibrium to the 

 second power, the formula of Biltz 



Cone, of free poison = A^(conc. of poison in the antitoxin )*, 



gives a value of / which rapidly sinks with increasing 

 concentration of the antitoxin. For the tetanolysin with 

 antilysin, / sinks from the value 4.5 through the values 



