Ill 



JIHEI KONISHI AND YNGVE ZOTTERMAN 



salt or non-electrolytes. Figure 7 illustrates the integrated responses to 

 varying concentrations of NaCl and sodium acetate of fishes adapted to 

 water or to isotonic saHne solution for more than one week. No response 

 to distilled water was observed in the fish adapted to isotonic saline. The 



Na -Acetate 



Cone. (/©/ 



Fig. 7. Response of the entire palatine nerve of the carp to varying concentra- 

 tions of NaCl (open circles) and sodium acetate (solid circles). Upper two 

 curves, responses from the carp adapted to water ; Lower two curves, responses 

 from the carp adapted to isotonic saline more than one week. 



mechanism involved in the positive response caused by a water stimulus 

 after a previous application of salt is not yet clear. From our experiments 

 it seems unlikely that it is the outflow of ions through the receptor mem- 

 brane which aff'ects the receptor excitability in the fish. The excitation pro- 

 duced by water must be mediated by a rather different mechanism than that 

 involved in the so-called water response in other animals. The fact that a 

 previous application of non-electrolytes, which hardly can diffuse into the 

 receptor cell, also eHcited large responses to water, even much larger than 

 that after salt, seems to support such a view. 



As is seen from Fig. 7, the fibres in the fish adapted to isotonic saline show 

 responses to dilute NaCl solutions that are rather smaller than the res- 

 ponses to distilled water, indicating a depression of the effect of NaCl, 

 while sodium acetate almost has no depressing action. In this respect the 



