PHYSIOLOGY OF GUSTATION 155 



stimulus to a gustatory portion of the tongue and the 

 response of the subject. He used an electric current as a 

 stimulus and found the average time to be 0.167 seconds. 

 Von Vintschgau and Honigsehmied (1875-1877), who used 

 solutions of various substances as stimuli, found that the 

 times were different for the different tastes, being short- 

 est for saline, longer for sweet, still longer for sour and 

 longest for bitter. They also discovered that the times 

 were different for the tip of the tongue and its base. 

 Their results were confirmed in general by the later in- 

 vestigations of Beaunis (1884), of Henry (1895) and of 

 Kiesow (1903) who recorded the following periods for 

 the tip of the tongue : 



Sodium chloride 0.308 second 



Sugar 0<446 second 



Hydrochloric acid 0.536 second 



Quinine 1-082 second 



These records agree with Schirmer's observation 

 (1859) that when a solution containing all four sapid sub- 

 stances is placed on the tongue, the subject experiences 

 the sensations in the order saline, sweet, sour, and bitter. 

 They also confirm the opinion that the four tastes are 

 separate entities. 



One aspect of the problem of gustatory latency turns 

 on temperature. If the stimulation of a taste receptor 

 is a chemical operation, this process should exhibit a con- 

 siderable temperature co-efficient that might make itself 

 felt in a change in the latent period. But so far as I am 

 aware no studies with this point in view have been car- 

 ried out. 



13. Taste Alterations; After-tastes. A number of 



