The function of Jacobson's (vomeronasal) organ in mammals has intrigued man for more than a century, despite the fact that he does not have this sense organ at his disposal. Two ideas gradually developed about its possible function: the morphology of the organ suggests that it is especially appropriate to receive non-volatile chemical stimuli. Secondly it might have to do with the reception of sexual pheromones.
The aim of this study was directed towards both assumptions. Observations of cats show that the way of sniffing at several odours and especially urine, suggests an uptake of dissolved particles. The observations as described in Part I indicated that urine of estrous ♀♀ positively influences the frequency of flehmen in tomcats. These results, combined with the effect of experimental blocking of the entrance of Jacobson's organ on this behaviour supported both ideas referred to.