182 H. T. ANDERSEN, M. FUNAKOSHI AND Y. ZOTTERMAN 



were equally strong, whereas D-glucose and especially D-galactose elicited 

 relatively small responses. The other type of fibre which was activated 

 only by stimulation with D-fructose is shown in Fig. 4. 



Neither one of these two fibres responded to water, 0.5 m sodium chloride 

 or 0.01 M quinine solutions. 



(ii) Disaccharides. An example of the electrical activity in specific sweet 

 fibres upon stimulation of the tongue receptors with the three disaccharides 

 is shown in Fig. 5. The results obtained confirmed the integrator-record- 

 ings, namely, sucrose produced the largest response of these three sugars, 

 lactose the smallest, with that of maltose falling in between. Another 



iiliii ill \ I 



Maltfius 



iiiHiHiiii iiimi 



JLactose 



I i Mil 111 



Fig. 5. Electrical responses from single fibre recorded upon application of 0.5 m 

 solutions of the disaccharides to the tongue. Time in seconds. 



feature of Fig. 5 which is noteworthy is that the period of time which 

 elapsed from the application of the sapid solutions to the tongue until the 

 response could be recorded was shortest in the case of sucrose. 



(iii) Complete sugar series. Figure 6 shows the responses recorded after 

 stimulation with the complete sugar series. D-fructose again produced the 

 most conspicuous response in terms of spikes per unit time. Sucrose was 

 second in stimulating ability, next followed by D-glucose, D-galactose, 

 L-sorbose and maltose. Lactose and D-mannose elicited the smallest 

 responses in this experiment. 



(iv) Unspecific fibres. Certain fibres were activated by a 0.5 m NaCl solu- 

 tion as well as by the sweet stimuli. An example is given in Fig. 7. How- 

 ever, among the sugars only D-fructose and sucrose were able to produce a 

 discharge of electrical activity in this preparation ; that of D-fructose was 

 by far the largest, while sucrose and sodium chloride elicited exactly the 

 same response in terms of spikes per unit time. 



We have seen that there is a very good conformity between previous 

 psychophysical findings in human subjects and our electrophysiological 

 data from the dog (Table 1). Whereas the over-all picture is very 



