THE NASAL REGION IN EUTAENIA. 40] 
constituents in the floor are formed by ciliated epithelium cells, 
which are also abundantly found on the palate immediately anterior 
to the choanae. In the choanal depression, minor folds of the mem- 
brane are very abundant. The two large ones separating the choanae 
enclose a cul-de-sac, whose lining membrane contains a profusion of 
goblet cells, which, however, give place to ciliated epithelium cells 
at the opening. 
The Organ of Jacobson (Fig. 2, J. O.) is with its pedicle of semi- 
circular shape in transverse section, the cellular columns of its roof 
appearing to radiate about the crescentic lumen of the canal, and to 
form the greater portion of its bulk. These are of greatest 
length on the inner and upper side at the opening, behind 
which they are found on all sides of the now oval lumen. (Fig. 4.) 
The crescent form of the canal in front is due to the growth in- 
ward on its floor of a projection from the palate, and filled out 
with cartilaginous and parosteal structures as described above. For 
want of a better term I have called it the pedicle. (pd.) It bears 
a marked resemblance to the turbinal, this similarity heing some- 
what strengthened when one considers the connection of their carti- 
lages, and that the Organ of Jacobson and the upper nasal chamber 
are functionally alike. The inner wing of the lumen of the canal 
becomes prolonged downward between the pedicle and the basal 
portion of the vomer, and opens in the groove to be found on the 
border between the middle palate and the palatine ridge. (Fig. 3, 
Jop.) This groove can without much difficulty be seen in hardened 
specimens, and in fresh ones only when the upper jaws are 
pressed upward, thus separating the palatine ridge and middle 
palate and exposing the groove. Behind this opening the pedicle 
disappears and leaves the canal oval im section. (Fig. 4). On 
its further course the columns arrange themselves on its under side, 
and are continued for some distance behind its blind termination. 
The lachrymal duct opens on the inner wall of the same groove in 
which the Organ of Jacobson opens. (Fig. 3, Zop.) It runs behind 
under the organ as far as it is continued behind, when it gives a 
sharp turn outward toward the palatine bone. A longitudinal section 
of the duct is illustrated in Fig. 11. There a represents the basal 
portion of the duct which lies partly under the vomer and partly 
beside the palatine bone, and ends blindly behind (6). The main 
duct is continued upward and outward over the palatine, where a 
