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. Ata 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 pe.) 
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 
