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MASAYASU SATO 



ture is 10° or 40'C. The unit shown in d responds to temperature change 

 only. However, it may be possible that this unit responds to taste solutions, 

 if we had employed NaCl, quinine or HCl of higher concentration as 

 stimuli than that employed for testing this unit. Furthermore the fre- 

 quency of impulses shown in this unit is not greater than that shown in a 

 and therefore the unit shown in d cannot be considered the unit specifically 

 sensitive to temperature change. These results suggest that there are few 

 units in the chorda tympani which are exclusively sensitive to taste stimuli 

 or to temperature change. 



Responsiveness of units to 1/2 m NaCl, quinine, 1/256 m HCl and water 

 is shown in Table 2. Results shown in this table agree with those by 

 Cohen et al. (1955). Units sensitive to NaCl, quinine or water are relatively 



Table 2. Afferent fibres in the chorda tympani classified from their responsive- 

 ness TO four kinds of taste stimuli (Nagaki, Sato and Yamashita, unpublished). 



Stimuli/ 



Sensitivity 



Number of units 



NaCl i Quinine 



HCl 



Cooling I Warming 



NaCl-sensitive units : 7 



Quinine-sensitive units : 8 



HCl-sensitive units : 1 1 



Sensitivity + -^ : indicates initial impulse frequency of more than 15-20 /sec to 1 /2 M 

 NaCl. 1/256 m quinine, 1/256 m HCl and water, +:5 — 15 /sec, ±: 1 — 5 /sec and 



-:0/sec at 30°C. 



