ELECTROPHYSIOLOGICAL RESPONSES TO SUGARS 189 



pre-treatment with 0.5 m NaCl is evident, but after a water-rinse, the normal 

 response reappeared (Fig. llC). 



(ii) Sugar-salt fibres. The recording obtained from a type I fibre is shown 

 in Fig. 12. The 0.5 m solution of sucrose elicited a conspicuous burst of 

 electrical activity in the fibre when applied to the tongue, whereas the mix- 



Fig. 11. Records from a single " sugar *' fibre. Response to 0.5 m sucrose is 

 inhibited by previous 0.5 m sodium chloride. Time in seconds. 



-^ — I I pr iiii n iii ju il j !! I I I HfM "" 



A 



B 



M;.ri , . Mixture , 



^ "IM II ii >l I n il I ll l l fl lll l f"'!M I I 



Fig. 12. Responses recorded from a single " sugar-salt " fibre (type I) upon 

 application of 0.5 m mixture after 0.5 m sucrose (A) and 0.5 m sodium chloride (B). 



Time in seconds. 



ture which followed produced a relatively small, but significant extra effect 

 (Fig. 12A). The sodium chloride solution alone gave only a small effect 

 in terms of electrical activity recorded from the fibre, but it depressed the 

 response to sucrose markedly as seen from the relatively modest response 

 to the mixture which followed (Fig. 12B). 



An example of the response pattern of a type II fibre is furnished in Fig. 

 13. Sucrose gave a very small response in this preparation, whereas the 

 sodium chloride had a marked ability to stimulate. In accordance with 

 these characteristics mixture after sucrose activated the fibre conspicuously 

 (Fig. 13 A), while mixture after sodium chloride had only a relatively slight 

 additional effect (Fig. 13B). 



The peripheral depression of the sugar response by salt was clearest seen 



