TASTE FUNCTIONS IN FISH 227 



selective adaptation was also found in the response to the pupa fluid follow- 

 ing previous application of the saliva (Fig. 1 1 — ^11). These findings strongly 

 suggest that the receptors responding to saliva are commonly stimulated 

 by the sapid substances mentioned above and, in addition, the main 

 gustatory active component in all these substances probably belongs to the 

 same or a similar group. However, the fractionation of the residue of the 



Fig. 10. Electrical response from the carp's palatine nerve to the application 



of the human saliva which contains specific blood group substance. A, saliva 



with blood group substance of type A ; O, saliva with that of type O ; B, saliva 



with that of type B. Time in 0.5 sec. 



ethanol soluble fraction of the pupa by ether revealed that the gustatory 

 active substance occurs in both the ether soluble and insoluble fractions, 

 suggesting the presence of at least two main active components in the pupa, 

 and that one of them might belong to a group similar or related to that in 

 saliva (Fig. 9). Both fractions had a potency similar to the original pupa 

 extract. Molisch' reaction and BiaFs orcin reaction were strongly positive 

 in the ether insoluble fraction, and very weak positive in the soluble 

 fraction. 



