254 R. L. KITCHELL 



solutions over the caudal part of the tongue often did not elicit in a response 

 (Figs. 14 and 15). Movement of a vallate papilla regularly elicited a phasic 

 response (Fig. 14a). If a test solution was flowing over the papillae when 

 they were being moved the response to mechanical stimulation was followed 

 by a second response of longer duration. This phenomenon was first re- 

 ported by Appelberg (1958) and was related to the fact that the taste buds 

 associated with the vallate panillae are located near the base of the moat 

 which surrounds the papillae. He presented the hypothesis that movement 

 of the papilla opened the moat and thereby permitted the test solutions to 

 contact the taste buds. Our results have confirmed his observations (Figs. 

 14-16). Movement of a vallate papilla during the application of distilled 

 water or Ringer's solution did not elicit a detectable secondary discharge 

 which could be related to the application of these solutions (Figs. 14-16). 

 Striking secondary responses were observed in goats during the time the 

 various test solutions were being applied (Fig. 14). The magnitude of the 

 integrated responses which followed the application of 0.46 m sucrose and 

 of 0.02 M quinine hydrochloride were of interest considering the low mag- 

 nitude of integrated response observed in the chorda tympani nerve follow- 

 ing application of these test substances to the rostral areas of the tongue in 

 goat. 



Results obtained in the pig (Fig. 15) indicate that the neural responses in 

 the lingual branch of the glossopharyngeal nerve following the application 

 of 0.5 M sodium chloride and 0.2 m acetic acid to the caudal part of the 

 tongue while moving the vallate papillae are smaller than those following 

 the application of 0.46 m sucrose and 0.02 m quinine hydrochloride. 

 Further studies in this species are contemplated. 



In conclusion, comparative anatomical and physiological observations of 

 gustatory mechanisms have been presented. In particular the myelinated 

 fiber diameter spectrum of the chorda tympani nerve in several domestic 

 animals has been presented. Neural responses recorded from the chorda 

 tympani and the hngual branch of the glossopharyngeal nerves following 

 the appHcation of various test solutions has been described. The need for 

 caution in arriving at conclusions based upon comparative phenomenal 

 events is emphasized. This does not preclude the importance of recording 

 and describing phenomena but only emphasizes the need for considerate 

 and thoughtful judgements before generalizations from specific pheno- 

 mena are made. 



REFERENCES 



Anderson, B., Landgren, S., Olsson, L. and Zotterman, Y. 1950. The sweet taste fibers 



of the dog. Acta Physiol. Scand. 21, 105-1 19. 

 Appelberg, B. 1958. Species differences in taste qualities mediated through the gloss- 



pharyngeal nerve. Acta Physiol. Scand. 44, 129-137. 



