82 THE THEORY OF IONS 



must be due to the ions. A pure ion effect parallels 

 the ionic concentration, and not the concentration 

 of the salt in the solution. Cations and anions in 

 many instances antagonise one another ; and the 

 effect of a salt upon various substances, e.g. protein, 

 is the sum of the effects of different ions. 



We are far from a satisfactory insight into the 

 nature of the effect of ions, which may be chiefly 

 electrical in character and brought about by the 

 polarity of matter. Nevertheless examples of such 

 ion effects are to be found in pharmacology of the 

 iodides, cocaine and other drugs, in the absorption 

 of water by muscle, in the sense of taste, changes 

 in the state of the proteins, etc. In the living 

 organism we have to deal with complex mixtures 

 of crystalloids and colloids, between which there 

 exist relations so intimate and varied that some of 

 them are still incapable of elucidation. " Connected 

 with the uninterrupted vital activity of the cell, the 

 anabolism and catabolism of its substance, is the 

 conversion of crystalloids into colloids, and colloids 

 into crystalloids ; and this at present unexplained 

 transformation serves at one time to protect a sub- 

 stance from oxidation, as in the conversion of 

 crystalloidal sugar into colloidal glycogen ; at 

 another time it protects the protoplasm against 

 the poisons of its own products."* These changes 

 are brought about by the addition or abstraction 

 of ions from the molecule, by addition or subtrac- 

 tion of side-chains, and by intra-molecular changes 

 dependent upon the electrical condition of the 



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

 p. 43. 



