THE NASAL REGION IN EUTAENIA. 391 



"backwards and inwards across the axis of the depression. (Fig. 1.) 

 It is due to a folding of the mucous membrane into crypts. The 

 middle palatal depression is bounded anteriorly by a raised portion 

 of the palate from which a crest, large, rounded in front, is continued, 

 diminishing in height as it proceeds backward. Behind the palatal 

 depression lies the choanal region, oblong in shape, and much deeper 

 than the rest of the upper surface of the mouth. It contains the 

 somewhat crescent-shaped choanae and the choanal cul-de-sac, the 

 latter to be found between two folds separating the choanae, diverging 

 and flattening out posteriorly. At a point on the middle palatal de- 

 pression on each side of the palatal crest, opposite its posterior termina- 

 tion and adjacent to the palatine ridge, is to be found, in hardened 

 specimens, a very delicate groove, containing the openings of the 

 Organ of Jacobson and the lachrymal duct. 



The corneous matter covers the edge of the lips to the lateral 

 "border of maxillary ridge. At this junction of the corneous and 

 maxillary regions the apertures of the ducts of the upper lip gland 

 are found. 



In a transverse section of the nasal region of the adult, through 

 the middle of the Organ of Jacobson, the latter is situated immedi- 

 ately above the palatine ridge and the middle palatal depression on 

 each side of the middle line, and placed adjacent to the inner wall of 

 the nasal passage, which is here inclined outward and downward. 

 Laterally from the Organ of Jacobson and under the nasal passage 

 lies a cavity with its transverse axis horizontal, which may be termed 

 the maxillary sinus. Above it Miiller's Nasal Gland covers the 

 lateral wall of the nasal passage. (Fig. 2, Mg.) Immediately above 

 the inner corneous portion of each lip is seen the upper lip gland 

 with several lobules. Below, the maxillary and palatine ridges are 

 strongly marked, and the middle palatal surface has a distinct crest. 

 (Fig. 2, m, p, and pc.) 



The vomer is double, each half forming a capsule for the inner 

 and a portion of the under and upper walls of the Organ of Jacobson 

 of its side, and consisting of three portions, a basal not quite horizon- 

 tal, a thin vertical plate concave on its outer face, and a cupped 

 ■crest. The inner edge of the septomaxillary, appearing in section as 

 if turned under on itself, rests on the cup of this crest, and the septo- 

 maxillary is continued from here outwards between the Organ of 

 Jacobson and the nasal passage. Under the latter, it gives two 



