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. 0.) 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 pi'olonged 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 in 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, Lop.) 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 (b). The main 

 duct is continued upward and outward over the palatine, where a 



