68 DON TUCKER 



ficial petrosal nerve at the point where it arises from the facial nerve. The 

 sympathetic nerve was sectioned centrally whereas the facial nerve was not. 



SYMPATHETIC 



--^-^^-^Hhljl^'Mf^^ 





-J^fi|^^Wy)|l^^Mr^ 



T — ^ — I — r-1 — \ — \ — ^ — I — \ — ^ — ^ — ' — r-^ — ' — ^ — ^ — r 



I APPROXIMATE ' 



T 



Fig. 21. Postganglionic autonomic responses recorded from ethmoidal nerve 

 twig for stimulation with 2 msec pulses at preganglionic sites. 



CONCLUSION 



The kind of odorant and its concentration in the air inspired into the 

 nose rank as obvious determinants of nasal chemoreceptor responses. 

 With these must be classified the volume flow rate of odorous medium into 

 the naris. Either the rate of delivery of odorant molecules to an olfactory 

 receptor or the effective concentration attained at the receptor within a 

 characteristic time must be the crucial factor for generating the phasic 

 response. The latter alternative is consonant with the phasic olfactory 

 response data for the tortoise. But it is interesting that Stuiver (1958) 

 chose to consider the stimulus in terms of the rate of absorption of odorant 

 per unit time and mucosal area. He devised an ingenious equation that 

 exhibits flow rate dependence and plateauing behavior, but his assumption 

 that all odorants should be quantitatively similar in these respects appears 

 inconsistent with the results for amyl acetate and benzyl amine shown in 

 Fig. 13. Nevertheless, the idea is expressed clearly that odorant is lost 

 from the flowing medium to the mucous membranes lining the nasal 

 passages. Therefore, odorant concentration is progressively reduced at 

 more downstream points. 



The assumption that concentration equilibria are quickly established 

 between the media of the inspired air, the mucus and the receptor sites 

 (Moncrieff, 1955 ; Davies and Taylor, 1957) appears most applicable to 

 odorants that are slightly soluble in the mucus. Perhaps one should 



