100 THE THEORY OF IONS 



protein precipitation is markedly increased."* In 

 the case of living animals only the former possibility, 

 that of the presence of a low concentration of ions, 

 comes into consideration. The iodides and still 

 more sulphocyanates "act under these circumstances 

 as substances which favour the formation of readily 

 soluble ion-protein compounds through which the 

 elimination of the heavy metals is greatly aided, "f 

 The relationship between the salts and esters was 

 studied by Pauli through the sulphocyanates. 

 Esters are combinations of an alcohol and an acid ; 

 they are scarcely dissociable into ions in aqueous 

 solutions, and there is a wide difference between 

 their power of entering the cells of an organism and 

 that of the ionisable salts. Overton has shown that 

 esters readily enter the cells because they are soluble 

 in the lipoids lecithin, cerebrin, cholesterin of the 

 cells. Salts on the other hand enter the protoplasm 

 with difficulty because of its comparative impermea- 

 bility to them. The ester enters the cell and be- 

 comes saponified by union with the lipoids, whereby 

 the anion of the acid is set free, and a physiological 

 anion effect follows. Pauli found for instance that 

 if an experiment be made with sodium sulphocyanate 

 and the amyl-ester of sulphocyanic acid, a character- 

 istic sulphocyanate effect will follow in both cases, 

 but while 2 or 3 drops of the ester will cause a fatal 

 intoxication in an animal, from 8 to 10 grains of the 

 salt must be injected subcutaneously to produce the 

 same effect. The ester enters the cell readily, and 

 the anion is not set free until it is within it ; but the 



* Pauli's " Physical Chemistry in the Service of Medicine," 

 p. 85. f Loc. cit. 



