ELECTROPHYSIOLOGICAL RESPONSES TO SUGARS 



191 



(iii) Salt fibres. The fibres which, by our criteria, were specific for salt 

 stimulation were never affected by previous application of 0.5 m sucrose 

 to the tongue. This is evident from Fig. 16A and B, in which the responses 

 of the fibre to 0.5 m NaCl after water and sucrose, respectively, are re- 

 produced. 



Fig. 16. Records from a single " salt " fibre showing that the response to 0.5 m 



sodium chloride is not affected by previous application of water (A) and 0.5 m 



sucrose (B). Time in seconds. 



The data presented in this section has been summarized in Fig. 17. This 

 schematic review of the electrical discharges from the various types of 

 functional single fibres studied explains readily the response patterns of 

 the integrated recordings which are shown at the bottom of the figure. 



The mechanism by which the salt solution exerts its inhibitory effect on 

 the sugar response is, however, not as easily revealed. As a matter of fact, 



Sucrose Mixture NaCl Mixture 



1 ' 1 ' 



Sugar fibre 



Sugar-salt fibre 

 type I 



type II 



type III 

 Salt fibre 



Sucrose Mixture 



III II I I 



11111 



NaCl Mixture 



Fig. 17. Schematical representation of response patterns of various types of 

 fibres and integrated responses to salt and sugar solutions. 



