272 MORRIS M. WELLS 



3. Resistance to sodium salts 



Experiments with the following sodium salts were performed 

 in tap water: bicarbonate, carbonate, chloride, nitrate, and sul- 

 phate. The solutions were O.OIN and the fishes small blue gills 

 (3-5 grams). The results were as follows: 



Salt used Resistance of fishes 



Sodium bicarbonate Normal at end of 15 days; discont. 



Sodium carbonate Dead after 3 days 



Sodium chloride Normal after 19 days; discont. 



Sodium nitrate Dead after 31 days; only 50 cc. water left 



Sodium sulphate Normal after 20 days; discont. 



From the above results we see that the sodium salts are not 

 toxic to blue gills when O.OIN concentrations are used in tap 

 water. The carbonate is an exception as the fish dies in this 

 solution in 3 days. It has already been shown (Wells '15 a) 

 that these fishes cannot live in water that is even faintly alkaline 

 and thus the action of the carbonate is due to its alkalinity. 



It will be remembered that the reactions of the fishes in salt 

 gradients were complicated by the antagonism between the 

 salts and the acid in the water. Loeb was the first to demon- 

 strate that there exists an antagonism between salts and acids, 

 as in 1899 he showed that acid antagonises the effect of NaCl 

 on the swelling of muscle. He suggested that the antagonism 

 depends upon the action of the substances upon the proteins of 

 the tissues. Again, Loeb and Wasteneys ('11 and '12) demon- 

 strated the antagonism between salts and acids, in their effect 

 upon the marine fish Fundulus and explained the effect as due 

 to a direct action on permeability. Osterhout ('14) made in- 

 vestigations which show that similar though less striking antago- 

 nism between acids and NaCl occurs in plants; he further states 

 that the antagonism is not as great as that between NaCl and 

 CaCls. 



To determine the relation of the antagonism between salts and 

 acids to the resistance of fresh water fishes, a series of experiments 

 was run with NaCl and HCl. Table 9 summarizes the results 

 of these experiments. From this table it will be noted that fresh 

 water fishes of the same species and size live much longer in toxic 



