42 PHYSICAL CHEMISTRY IN MEDICINE. 



kind of dissolved crystalloids (PAULI). The poisonous 

 effects of water poor in ions upon the human organism 

 (KOPPE) may also belong under this heading.* Differ- 

 ences in the concentration of ions brought about through 

 differences in their migration velocities constitute the 

 source of differences in electrical potential. LOEB was 

 probably the first who recognized in such " concentration 

 chains" the cause of the majority of the electrical phe- 

 nomena observed in animal organs. 



We are far from a satisfactory insight into the nature 

 of the effects of ions the elements of which may be 

 electrical in character. Nevertheless, we know enough 

 to be able to say definitely that a certain effect is quan- 

 titatively determined by ions, if it follows the general 

 principles outlined below: 



"Since very dilute solutions of electrolytes are almost 

 completely dissociated, the effects brought about by such 

 solutions may, as a rule, be looked upon as ion effects,, 

 and the electrically neutral molecules may be neglected 

 because of their exceedingly small number. A pure ion 

 effect must parallel the concentration of the ions and not 

 the concentration of the substance itself; and at the same 

 concentration of substance be dependent upon the degree 

 of dissociation, which can be varied, without a change in 

 volume, through the addition of an electrolyte having a 

 common or a different ion. When anion and cation 



* A specific ion effect is not, strictly speaking, proved by this experi- 

 ment, because the attempt to do away with the poisonous effects of the 

 water through the addition of non -ionized substances such as sugar 

 was not made. Moreover, NANSEN and his followers in his polar expe- 

 dition drank for months without harm the almost ion-free water ob- 

 tained by melting natural ice. 



