Evaluating hypotheses for the transfer of stimulus particles to Jacobson's organ in snakes

Six hypotheses for transfer mechanisms to the sensory epithelium of Jacobson's organ are presented: diffusion, capillary action, ciliary currents, pinocytotic currents, direct tongue insertion, and suction. Of these, diffusion and capillary action are rejected on theoretical grounds, and ciliary and pinocytic currents are seen as playing, at best, a secondary role. Of the two remaining hypotheses, direct insertion of the tongue and suction, experimental evidence is summarized that leads to the rejection of the direct insertion hypothesis. The stimulus transfer mechanism is hypothesized to involve the generation of suction within the lumen of Jacobson's organ and its duct. It is proposed that this suction is produced by pressure from the tongue and/or the anterior lingual processes.