160 JOHN N. LOWE 



The more negative the value for the ionic potential the greater 

 the solvent power of the salt for edestin. The negative value in 

 potassium is much greater than that in the sodium. In the table 

 we observe that it takes like amounts of the iodides and less of 

 the other sodium solutions to dissolve the edestin. However, we 

 should expect it to take less of the potassium salts than it does 

 of the sodium. I find this to be true for the pigment cells of 

 trout, where the potassium salts cause the contraction of the 

 pigment cells more rapidly than do the salts of sodium.^ Un- 

 fortunately the solutions tensions for sodium and potassium are 

 more or less indefinite which makes the results obtained for the 

 salts of these metals incomparable. The ionic potential is not 

 ■ determined directly, but calculated only, thus making the ex- 

 planation more difficult. 



The results obtained in experiments on the action of salts on 

 the pigment cells of trout are explicable on three assumptions; 



(1) that it is the antagonistic action between anion and cation, 



(2) that it is the independent action of the cation, (3) that the 

 reaction is modified by the residual undissociated molecule. 



The antagonistic action between anions and cations has been 

 postulated by Mathews ('06), Benedict ('05, '08), and W. Koch 

 ('09). The increased action of different salts having the same 

 cation have been observed in different tissues. Loeb ('99) pro- 

 duced a better rhythmical contraction in striped muscle with 

 Nal than he did with NaCl. Zoethout ('04) confirmed this ob- 

 servation, and extended it to KI which increased the muscle 

 tone more than KCl. Benedict ('08) concluded that "the direct 

 production of rhythmic activity by means of a salt's action upon 

 heart muscle is due to the anion of the salt, while the chief 

 function of the cation is apparently to maintain such a tone of the 

 heart muscle that it will respond to the stimulus furnished by 

 the anion." Mathews ('02) has shown that the presence of 

 iodine, bromine anions stimulated the motor nerve more power- 

 fully than the chlorine anion. Speath ('13) observed that the 

 cytolytic expansion of the melanophores in potassium solutions, 

 varied with the anions, but he did not note a difference in the 

 rate of the primary contraction of the melanophores in the 



