RESPONSES TO ODORANTS 53 



adjustment of the stimulus to yield moderate responses from either or both 

 kinds of receptors. The vomeronasal response tends to predominate for the 

 lower members of a homologous series of compounds. It is larger for 

 methanol and ethanol as shown in Fig. 8 and for all the succeeding alcohols 



M ' ZrJlT*'^ ¥ ^ ^i^ i ^ffi^^ 





PROPANOL 



^m m m t mmmm^ k m , m ^)l »mii$llllf ^ ^ 



aUTANOL 



Fig. 8. Vomeronasal (first trace of each pair) and olfactory responses recorded 

 simultaneously. Differential nature of the responses is illustrated. 



the olfactory response is larger. In the fatty acid series the cross-over from 

 vomeronasal to olfactory predominance occurs in going from /^r;-valeric, 

 after /7-butyric, to /7-valeric acid. The olfactory response is larger for the 

 acetate esters of all the aliphatic alcohols. 



The vomeronasal organ, or organ of Jacobson, in Gopherus opens into 

 the nasal cavity via a tubular duct that is relatively small. One might 

 expect that the olfactory receptors should be more readily stimulated, but 

 no consistent difference in latency between responses of the two kinds 

 was seen (Fig. 9). How can odorant molecules penetrate to the sensory 

 epithelium lining the organ of Jacobson as readily as to the much more 

 accessible olfactory organ ? 



The vomeronasal organ is housed in a projection from the wall of the 

 nasal septum. This projection has the appearance of a baffle, such that the 

 respiratory passageway is deflected laterally before descending on its route 

 to the choana in the roof of the mouth. The histological section shown in 

 Fig. 10 is through the organ at a level where the vomeronasal nerve is 

 breaking up into branches. Notice the proximity of the epithelial surface 



