244 THE VISCERA. 
the horizontal plate formed by the vomer and ethmoid, and 
opens caudad at the choane into the nasopharynx. The 
dorsal or superior meatus of the nose lies just ventrad of the 
superior nasal concha, next to the median septum; it leads to 
the frontal sinus, the lamina cribrosa, and the caudal parts of 
the ethmoid. The middle meatus of the nose has almost dis- 
appeared in the cat; it is simply the narrow space between the 
superior and inferior meati. It is practically filled by the 
ethmoid, into the cells of which it leads. The mucosa is con- 
tinued from the nasal cavity into the sinuses of the frontals and 
presphenoid. 
At the sides of the nasal septum, near the ventral edge, 
and about one to one and a half centimeters caudad of the 
nares, there is on each side a small curved cartilaginous tube, 
about one centimeter or less in length. This, the vomeronasal 
organ, or organ of Jacobson, lies against the septum, between 
it and the mucosa. It begins at the incisive canal or anterior 
palatine foramen, in the roof of the mouth, curves thence 
caudodorsad close against the side of the nasal septum, and 
ends blindly in the nasal cavity. 
The nares ‘or cranial openings of the nasal cavity are sup- 
ported by a number of cartilages which form the framework of 
the snout or external nose. The cartilaginous continuation of 
the lamina perpendicularis extends some distance craniad of 
the tips of the nasal and premaxillary bones, forming the 
septum of the external nose (Fig. 103, a). 
From the dorsal edge of this projecting car- 
tilaginous septum, two thin cartilaginous wings - 
(6) extend laterad, forming the dorsal wall of 
Fic, 103. — Cross- the narial opening. Each then turns ventrad 
ee go to form the lateral wall of the opening, but 
fee EXTERNAL does not form the ventral floor; instead it 
a, cartilage of the curves mediad and finally dorsad, thus ex- 
medion. papi, mi tending from the floor of the opening as a 
Pi by detec prominent ridge (c) within the nares. The 
portion of wing. cartilaginous wing is thus rolled into a sort of 
spiral, ending with a free edge within the narial opening. 
From the ventral edge of the median cartilaginous septum there 
