248 R. L. KITCHELL 



Beidler, 1953 ; Kitchell, 1961). Beidler (1953) initiated the use of an inte- 

 grator as a method of quantifying neural responses in the chorda tympani 

 nerves. The integrator has been proven to be a useful instrument by a 

 number of investigators. It is of considerable importance that during a 

 test series, all other variables are kept as constant as possible (Kitchell, 

 1961). In making comparisons among species, using whole nerve pre- 

 parations, consideration must be given to the fact that what is being re- 

 corded are electrical phenomena involving recordings from an isolated 

 nerve trunk. For example, in multifasciculated nerves, the amount of 

 epineurium and the quantity of interstitial fluid may markedly alter the 

 size of the recorded potentials. Many factors may influence the direct or 

 integrated response. The magnitude, duration or other characteristics of 

 a response, integrated or otherwise, bears no simple relationship to sen- 

 sation. This is in no way a denial that certain anatomical features or 

 electrophysiological phenomena do not exist and are not reproducible. 

 The interpretation of these phenomena may lead to serious errors. 



In our experiments, the test solution is applied to the tongue by means of 

 a dispensing burette. The quantity and rate of flow of test solution dur- 

 ing a series is kept constant. The tip of the burette is adjusted prior to the 

 beginning of a series in order to reduce to a minimum the activation of 

 mechanoreceptors. The lucite flow chamber designed by Beidler (1953) 

 reduces the initial activation of mechanoreceptors but if the concentration 

 gradient changes rapidly some activation of mechanoreceptors due to 

 flow of the solution across the tongue may occur. In our experiments, 

 using a dispensing burette and photographic recording of both the direct 

 action potentials and the integrated response, the phasic response is 

 accentuated. The static response can be analysed by either decreasing the 

 rate of flow from the burette or increasing the quantity of the solution in 

 the burette, or both. The flow chamber has the advantage of exposing a 

 larger surface of the tongue to the test solution than is possible with the 

 dispensing burette, particularly in animals with large tongues. This may 

 account for some of the dilferences such as concluding that "no" response 

 occurred following the application of a test solution using a dispensing 

 burette while other investigators using a flow chamber state that " slight ", 

 " mild ", or " weak " responses are observed. The flow chamber method is 

 of limited value in studies of phasic responses. 



The first step in investigating neural responses in the chorda tympani and 

 glossopharyngeal nerves was to determine if a neural response resulted 

 following the application of distilled water to the tongue. Zotterman 

 (1949) reported a response in the glossopharyngeal nerve in the frog to the 

 application of distilled water (distilled water response) to the tongue. Dis- 

 tilled water responses have been reported in the cat, dog, and pig (Lilje- 

 strand and Zotterman, 1954), the rabbit (Zotterman, 1956), the pigeon and 



