THE NASAL CAVITY. 



22 = 



than the other. A ridge is often found at or near the junction of these two bones 

 on the prominent side, thereby still further reducing the smaller cavity. This ridge 

 may be developed into a shelf, called a spur, which may even touch the opposite 

 wall. The outer wall is the most instructive, as giving the most light on the con- 

 struction of the region. In front is the smooth- walled vestibule, formed by the 

 inner side of the nasal and the ascending process of the maxilla, extending upward 

 under the frontal sinus. The swelling known as the agger may be found near the 

 top of its outer wall. The inferior turbinate is much the largest, reaching forward 

 almost to the opening in the bone. The large inferior meahis which it overhangs 

 is higher in front than behind. The middle turbinate, over the middle meatus, does 

 not extend nearly so far forward. The little superior turbinate with the limited 

 superior ineatus below it is still farther back, reaching only half-way along the 



Fig. 257. 



Spheno-ethmoidal recess 



Crista salli 



Frontal sinus 



Extension of sphenoidal sinus 

 Pituitary fossa 

 ' Sphenoidal sinus 



Spheno-palatine 



foramen 



Sup. turbinate y 



Middle 



turbinate 



Middle meatus 



Inf. turbinate 



Inf. meatus 



Anterior 

 palatine canal 



Hamular process 



Palatal plate of sup. maxilla 

 Inner aspect of outer wall of right nasal fossa. 



middle turbinate. The three turbinates end behind very nearly in a vertical line, 

 the middle sometimes projecting farthest. The lines of attachment of the turbinates 

 all slant downward and backward, but the inclination of the middle one is greatest. 

 The variations in number of the turbinates and the structures concealed by the 

 middle one have been described with the ethmoid. The spheno-ethmoidal recess is a 

 lateral expansion of the cavity behind the superior turbinate and the front of the 

 body of the sphenoid. The posterior portion of the outer wall of the nasal chamber, 

 formed by the palate bone and the internal pterygoid plate, is smooth. The outer 

 wall slants inward, so that the roof of the nasal cavity is narrower than the floor, 

 and has the following openings: in the superior meatus that of X^o. posterior ethmoidal 

 cells ; farther back is the spheno-palatine foramen communicating with the spheno- 

 maxillary fossa. The middle meatus receives the opening of the frontal simis either 

 directly under the front of the middle turbinate or through the i7ifimdibulum. 



15 



