TASTE FUNCTIONS IN FISH 221 



gustatory nerve fibres. Such an arrangement would thus be similar to 

 Granit's system of dominators in the retina. Specific taste fibres corres- 

 ponding to Granit's modulators we found only to salt, acid and to human 

 saliva. In addition to these we have the fibre type which responds only to 

 quinine and acid (type V) and type III fibres. From these findings it is 

 possible to picture a mechanism enabling the fish to elaborate a fairly high 

 level of gustatory discrimination. 



A Saliva 



B NaCl 



C Sucrose 



M 



D Quinine 



E Acid 



*^ 



Fig. 6. Response of single palatine nerve fibre classified under the type VI to the 

 application of various solutions to the palatal organ. Time in seconds. 



The question naturally arises as to whether the fish has receptors which 

 respond to water or not. Chemoceptors of the fresh water fish are naturally 

 exposed to water. All of the foregoing experiments, therefore, have been 

 undertaken with fish which were adapted to water. Under this condition 

 no fibre responding to water was observed. However, water sometimes 

 produced a response when applied shortly after a previous application of 

 salt (or even Ringer's solution), sucrose, acid, and especially strongly after 

 saliva. This response to water, however, is rather diff'erent from the water 

 response reported in other animals with respect to the following fact : The 

 response to water in the fish was only seen after the previous application of 



