106 THE THEORY OF IONS 



inhibited the depressant effect of K and Ba. In 

 these observations we see the effect of cation and 

 anion. The positive electrical charge of the metallic 

 ion counterbalances the negative electrical charge 

 of the native protein. Many of the cations increase 

 the irritability of both muscle and nerve. The ions 

 of Ba, Ca, and Sr stand between the alkali metals 

 and the heavy metals as regards protein precipita- 

 tion, but they stimulate irritability. The anion 

 effect is seen in the depression which follows the 

 ions of the halogen compounds, unless it is over- 

 balanced by the metallic ion. 



Experiments showing the influence of ions upon 

 growth were made by Moore, Roaf and Whitley on 

 the tadpole of Rana temporaries and other cellular 

 structures.* Living cells are very susceptible to a 

 change in the proportion of H and OH ions, both of 

 which are toxic when the concentration exceeds a 

 certain degree. The toxicity of acid salts is due to 

 the H ion, of alkaline salts to the OH ion. An 

 increase of alkalinity tends to an increased cell 

 division or growth of parts ; but cell division becomes 

 irregular or ceases if the OH ions exceed a certain 

 concentration. Acids and acid-salts, on the other 

 hand, exhibit a retarding influence on growth, cell 

 development being arrested. Neutral salts do not 

 show much toxicity ; they have very little effect 

 until the osmotic pressure rises above that of the 

 body-fluids of the organism. When the isotonic 

 point is reached there is a short range at which 

 these salts are toxic, dependent upon the effects of 

 the metallic ion. Barium and ammonium are toxic 



* Brit. Med. Jour., 1906, ii., 1788. 



