NASAL CAVITIES 397 



and the atrium are the conchae with the intervening meatuses. 

 The superior concha (Fig. 155, 12), which projects from the 

 labyrinth of the ethmoid bone, is very short, and is placed 

 on the upper and posterior part of the lateral wall of the 

 cavity. Its free border begins a short distance below the 

 centre of the cribriform plate, and passes obliquely down- 

 wards and posteriorly to a point immediately below the 

 body of the sphenoid, where it ends. The middle concha 

 (Fig. 155, i 4 ) also is a part of the ethmoid. Its free border 

 begins a short distance below the anterior end of the cribri- 

 form plate, and at first takes a vertical course downwards ; then, 

 bending suddenly, it passes posteriorly, and it ends midway 

 between the body of the sphenoid and the posterior border 

 of the hard palate. The inferior concha (Fig. 155, 15) is an 

 independent bone ; it extends posteriorly upon the lateral 

 wall of the nasal cavity, midway between the middle concha 

 and the floor of the nose. Its lower free margin is some- 

 what convex downwards. 



Meatus Nasi. The superior meatus (Fig. 155, 13) is a short 

 narrow fissure between the superior and middle conchse. 

 The posterior ethmoidal cells open into its upper and anterior 

 part by one, or, in some cases, by several apertures. 



To bring these orifices into view, the superior concha should be 

 turned aside by introducing the blade of a pair of forceps under its entire 

 length, and forcing it upwards. Care should be taken not to injure the 

 mucous membrane more than is necessary. 



The middle meatus is a much more roomy passage which 

 extends posteriorly frotm the atrium, between the middle and 

 inferior conchae. 



The middle concha should be forcibly tilted upwards and posteriorly. 



The upper and anterior part of the middle meatus leads into 

 a funnel-shaped passage which runs upwards into the corre- 

 sponding frontal sinus. This passage, the infundibulum, con- 

 stitutes the channel of communication between the frontal 

 sinus and the nasal cavity. 



Upon the lateral wall of the middle meatus a deep curved 

 groove or gutter, which commences at the infundibulum and 

 runs from above downwards and posteriorly, will be seen. 

 In this groove, which is termed the hiatus semilunaris (Fig. 

 156), are the openings of the anterior ethmoidal cells and 



