CHEMICAL EQUILIBRIA 139 



immunity because they carry down with them the 

 complements, as was at first demonstrated by 

 Bordet and his pupil Gay. This effect is called 

 diversion of complements, and has been of a very 

 great use for diagnostic purposes, as in the Wasser- 

 mann reaction and similar cases. 



The formation of precipitates and their redissolu- 

 tion by addition of greater quantities of the precipi- 

 tating substance is very common in general chemistry. 

 Thus for instance salts of aluminium are at first 

 precipitated and then redissolved by alkalies, and the 

 same is the case with the salts of a great number of 

 other metals. In this case the precipitate is the 

 hydrate of the metal, and the dissolution depends 

 on the formation of an aluminate or an analogous 

 salt. 



I hope that this short exposition has been sufficient 

 to prove that the very same laws are valid for the 

 equilibria in which the antibodies and antigens enter 

 as for the equilibria studied in general chemistry. 

 The quantitative determination of these equilibria 

 leads to the conclusion that the antibodies are 

 not analogous to enzymes or katalyzers, as was 

 often maintained before, but really take part in the 

 equilibrium. 



