54 DON TUCKER 



at the posterior boundary of the nasal vestibular chamber. Although this 

 problem is still unresolved, I believe it likely that the vomeronasal nerve 

 innervates this highly accessible patch of tissue in the anterior part of the 

 nasal cavity. Actually, it is probably doubtful that receptors in the organ 

 of Jacobson proper were ever stimulated in these experiments. 



* m»mmm , Il | j( i i |»< i i ||l( | |||) )i0| » < i i^ 



SUTYRlCAClO 





GERANlOt 



Fig. 9. Same preparation as for Fig. 8. Inconsistent difference in latency between 

 vomeronasal (first trace of each pair) and olfactory responses is illustrated. 



Olfactory Study in Detail 



An apparent difficulty in the use of cold-blooded animals under anes- 

 thesia is the paucity of active respiratory movements. We tested tricaine 

 methanesulphonate (MS 222 — Sandoz), but it was difficult to keep the 

 animal at such a level of anesthesia that respiration was frequent but that 

 no struggling occurred. Figure 1 1 shows integrated olfactory responses 

 occurring during free respiration. Each increase in response coincides 

 with inspiration. The response is a function of the rate and depth of 

 inspiration, which can be vexing when the animal's breathing is irregular. 



Most experiments were performed with the animal tracheotomized and 

 under ethyl urethane anesthesia. The choana was cannulated and air was 

 drawn through the nose, which was fitted into a port in the side of a 

 cylindrical glass breathing chamber. Air flowed into the breathing cham- 

 ber at a constant rate of lOOcmVsec. That which was not drawn into the 

 naris passed the tip of the nose at right angles and exited freely to atmo- 

 spheric pressure. A flow-splitting system was arranged to switch between 



