ELECTROPHYSIOLOGICAL STUDIES 



197 



Responses to Sugars 



All responding preparations of the human chorda tympani reacted to 

 sugars and also to saccharin. The threshold concentration of cane sugar 

 lies just above 0.02 m in accordance with the threshold of 0.017 M obtained 

 by Heymans in psychophysical experiments on man (see v. Skramlik, 1926). 

 The response-molarity curve shows a rather straight line up to a concentra- 

 tion of 1 M sucrose (Fig. 3). 



The effects of different biological sugars were recorded in two cases 

 (Fig. 4). From the diagrams in Fig. 5 it will be seen that sucrose produced 



ARABI NOSr 



FRUCTOSE 

 M ANNOSE 



GLUCOSE 



GALACTOSE 

 SORBOSE 



SUCROSE 



MALTOSE 

 -s^w-Mo.w^ LACTOSE 



Fig. 4. 



Integrated records from the human chorda tympani in response to 

 various solutions of biological sugars. 



the biggest response, followed by that of fructose, mannose (which tastes 

 bitter), glucose and maltose, sorbose and arabinose and finally galactose. 

 The response of lactose was unexpectedly high (77 per cent of sucrose). 

 Except for this relative high value, the recorded heights of the integrated 



