REACTIONS OF FISHES TO SALTS 255 



4. Conclusions from reaction experiments 



We note from the data which have been given that fishes 

 are markedly sensitive to salts in solution and that they react 

 to them in a definite manner. They are negative to O.OIN 

 concentrations of most of the salts used, if in water which is 

 moderately acid; this is the normal condition in most natural 

 bodies of water. When the water becomes strongly acid, the 

 reactions of the fishes are modified and may be reversed by the 

 mutual antagonism which exists between salts and acids. So 

 far as these experiments show, this antagonism exists only be- 

 tween the salts of K and Na and carbonic acid. From the gen- 

 eral work upon the antagonism of salts, to be discussed later, 

 one would not expect the antagonism to extend to the salts of 

 Ca and Mg. In the reaction experiments it was seen that the 

 fishes are, in nearly all cases, positive to some concentration of 

 the salt in question. This positiveness is most noticeable in the 

 case of NaCl. Table 1 is introduced to summarize the reactions 

 of the fishes to O.OIN salt concentrations in the different kinds 

 of water used. 



B. ANTAGONIZING SALTS AND THE REACTIONS OF FISHES 



To determine whether or not fishes detect and react to com- 

 binations of salts in gradients, a number of experiments was 

 performed, based upon the phenomena of the antagonistic 

 reaction of salts, which are familiar to all biologists. These phe- 

 nomena in their simplest form are expressed in the antagonism 

 which exists between the salts of Na and K, on the one hand, 

 and Ca and Mg, on the other. There has also been found a 

 certain degree of antagonism between Ca and Mg in some cases 

 (Meltzer and Auer '08). Most of the work on the antagonism 

 of salts has been done either upon single organs as the heart, 

 or other muscle tissue, or upon developing eggs and embryos. 

 Certain combinations have also been shown to be best for pre- 

 serving the life of fishes and other fresh water animals in dis- 

 tilled water (Ringer, etc.). So far as I am aware, no attempt 

 has ever been made to determine the reactions of fishes to com- 



