THE NOSE. 385 



inner posterior ang-le it opens on the free border of the horizontal 

 partition between the superior and inferior sinuses ; this opening is^ 

 however, continued along- its roof, so that the lateral sinus opens 

 also into the superior sinus. 



b. The nasal cartilages. The two nasal cavities are completely 

 separated by the cartilaginous septiun (Figs. 238 and 239 S), and 

 are for the most part lined by cartilage. The anterior end is 

 formed of concave cartilages, while the posterior, being sitviated in 

 the sphenethmoid, is usually more or less ossified in the adult. The 

 posterior wall has two openings : a larger near the septum for the 

 olfactory nerve, and a smaller, more externally, for the nasal branch 

 of the trigeminal nerve. 



The anterior wall is more complex than the posterior, being 

 thicker in the middle than at the sides, and possessing three blind 

 sacs for the three sinuses. From the anterior wall two processes 

 project backwards between the sacs and enclose them more or less 

 completely. 



Of the three sacs or cavities only the lower is completely sur- 

 rounded by cartilage. The upper sac is in part bounded by a shell- 

 shaped, concave cartilage {Concha nar'mm, of various authors ; 0,v 

 lachrymale, Born), which covers it anteriorly and externally, and is 

 attached by a small base to the roof of the lower sac (Fig. 239, /), 

 its upper border bounding- the anterior naris (Fig. 15). The upper 

 and external parts of the upper sac have no cartilage. The carti- 

 lages of the outer wall of the lower, blind sac extend backwards to 

 the point where the maxillary sinus commences to descend : the 

 roof, however, is prolonged further backwards by two small cartila- 

 ginous processes ; the inner is short, the outer forms the roof of the 

 descending arm of the sinus, and joins a cartilaginous process, which 

 commences at the anterior portion of the roof of the nasal cavity, 

 passes backwards and downwards to a broad plate, and forms an in- 

 complete outer wall to the nasal cavity. There are also three carti- 

 laginous processes — a. One arising from the outer side of the floor 

 at the level of its junction with the anterior wall ; it is a flattened 

 process and passes outwards, and bifurcates at its end to meet the 

 premaxillary and maxillary bones (this is the Oberkieferfortsatz of 

 Ecker), (p. 28, Fig. 14 n")). /3. A delicate process on either side,, 

 described by Wiedersheim (see p. 280). y. The third pair of pro- 

 cesses are fully described for the first time by Born ; each arises at 

 the lower border of the corresponding Concha narinm, passes forwards 

 and downwards under the ascending process of the premaxillary to 



c c 



