THE PHYSIOLOGICAL EFFECTS OF IONS 479 



NO 3 and the SO 4 ion does not come into consideration. I 

 shall return to this point as soon as I have made further 

 experiments. 



It is self-evident, of course, that so close a relation as 

 proportionality between the velocity of migration and the 

 relative toxicity of the ions is to be expected only in those 

 ions which belong to the same narrow group; a group in 

 which the remaining characteristics of the ions are almost 

 identical and in which important differences exist only with 

 reference to atomic weight and velocity of migration. "What 

 has been said thus far holds only for the members of the Li 

 series or the Be series among themselves ; it would be wrong 

 to judge the relative toxicity of K and Ca on the basis of 

 the velocities of migration of their ions, because in doing 

 this new differences come into consideration; for example, 

 the difference in their valencies. It would be entirely 

 absurd to judge the toxicity of the alkaloids by the velocity 

 of the ions. 



This further fact is to be considered in judging toxicity, 

 that all our evidence is of a negative character the cessa- 

 tion of life or of individual functions, especially irritability. 

 The most widely differing circumstances may, however, 

 bring about this result. One poison may act by rendering 

 impossible processes of oxidation (for example, HCN, 

 according to Geppert) ; another may bring about molecular 

 changes which influence the transformations of energy in 

 the cell, etc. It is to be expected that different groups of 

 poisons bring about their toxic effects in different ways. 

 This is a further warning against a too sweeping generaliza- 

 tion of the relation between velocity of migration and 

 toxicity. We must finally not overlook the apparent ine- 

 quality in the permeability of the protoplasm for different 

 ions, a subject concerning which special experiments are yet 

 to be made. 



