232 JIHEI KONISHI AND YNGVE ZOTTERMAN 



The application of water to the palatal organ had no stimulating effect, 

 after a previous rinse with water. Swedish carp displayed a high gustatory 

 sensitivity to sugar and acid, and low sensitivity to quinine, while Japanese 

 carp had low sensitivity to sugar, but showed a high sensitivity to bitter 

 substances. The nerve preparations also responded very strongly to human 

 saHva. Earthworm, milk and silkworm pupa extract very strongly stimu- 

 lated the chemoceptors of the fish. 



2. A study of single fibre responses revealed that the fibres could be 

 divided into seven groups according to their response pattern. Besides the 

 fibres displaying a broad gustatory spectrum, saliva always stimulated 

 fibres which responded positively to sugar. Fibres which responded to 

 NaCl, acid, or quinine, did not respond to saliva ; those that responded to 

 sugar did respond to sahva. 



3. From experiments on selective adaptation, it was suggested that the 

 receptors responding to sahva are commonly stimulated by the sapid 

 substances which may attract fish, such as silkworm pupa extract. The 

 existence of specific receptors highly differentiated in order to respond to 

 specific components of powerful sapid substances such as the saliva is 

 discussed. 



4. Experiments were undertaken in order to find the gustatory active 

 component in human sahva. Various substances which are already known 

 to be present in the sahva could be eliminated. The final gustatory active 

 component in the saliva could not be identified, but it is an alcohol soluble 

 and ether and acetone insoluble substance which may contain mono- 

 substituted amide groups, carbohydrates and probably also long chain 

 hydrocarbons in its molecular structure. The active substance is not 

 destroyed by boiling. 



5. Fractionations with organic solvents revealed that silkworm pupa 

 extract has at least two main gustatory active components. From infrared 

 analyses, one of them might be a substance related to glycerophospholipid, 

 and another probably a substance related to sphingolipid. 



6. The effect of lytic agents on the chemoceptor activity in the fish were 

 investigated. It was found that receptors responding to sugar and sahva 

 are paralysed most quickly by treatment with sodium cholate, and that salt 

 and acid receptors are more resistant to this lytic agent. Prior to the 

 paralysing of the receptors, temporal enhancements of the sensitivity to 

 salt and acid were observed. 



REFERENCES 



Cohen, M. J., Hagiwara, S. and Zotterman, Y. 1955. The response spectrum of 

 taste fibres in the cat : A single fibre analysis. Acta Physiol. Scand. 33, 316-332. 



Danielli, J. F. 1951. Cytology and Cell Physiology (edited by Bourne). Chap. IV. 

 The cell surface and cell physiology, pp. 156-157. Clarendon Press, Oxford. 



