THE AMYGDALA IN AMPHIBIA 265 
Broman (’20) in a reexamination of the morphological and 
physiological relationships of the vomeronasal organs of mam- 
mals and reptiles has shown that in both of these groups this 
organ is normally filled with liquid, not air, and that there is a 
pumping mechanism by which the liquid olfactory medium may 
be alternately sucked into and expelled from it. This mechanism 
is very different in the two cases, but in both it appears to be 
under control and to act rapidly. 
In lizards and serpents there is a mechanism by which the 
liquids of the mouth cavity can be forced into and out of the 
vomeronasal organ, thus providing “an ideal mouth-smelling 
organ.” In mammals the pumping apparatus is much more 
complex and diversified in, different groups, in some species 
adapted to draw liquid olfactory media into the vomeronasal 
organ from the mouth cavity, in others from the nasal cavity, 
and in most cases from both of these cavities. Broman suggests 
that the liquid media derived from the respiratory passages of 
the nose enable Jacobson’s organ to function in macrosmatic 
mammals in ‘tracking’ by odors (Spiirsinn). In this connection 
it should be borne in mind that the ordinary olfactory epithelium 
of mammals is not directly excited by gaseous media, as some- 
times taught, but the odorous substances must first be dissolved 
in the liquid which bathes the olfactory membrane. Neverthe- 
less it is not improbable that the liquid of the respiratory pas- 
sages may absorb a larger amount of the odorous substances and 
this more concentrated medium, when sucked into the vomero- 
nasal organ, would give to the latter an enhanced olfactory 
efficiency as a distance receptor. 
Broman has not investigated the Amphibia, but from the ob- 
servations of Bruner already cited (p. 214) it seems very probable 
that aquatic ‘double-smelling’ Amphibia developed first a lateral 
diverticulum of the nasal sac in close relationship with the 
choana especially adapted to serve as a mouth-smelling organ, 
and that from this simple beginning the true vomeronasal organs 
of Anura and Amniota have been derived. Broman (’20, p. 188) 
himself reached a different conclusion, viz., “that the organon 
vomeronasale Jacobsoni is nothing other than the old water 
