Tin-: \osi-; 



mouth, where its terminal inn is marked l>y the incisive papilla. The incisive duct 

 indicates the position of the passage which originally connecled I he mouth and HUM-. 



The lateral wall (tig. 7(i!M presents, just within the nares a .slight depression, the 

 vestibule. This corresponds to the expansion of the; ala. and is marked off from the 

 rest of the nasal fossa by a distinct ridge, the limen nasi. The area immediately 

 superior and dorsal to the vestibule is separated into * wo shallow depressions by an 

 oblique ridge, the. agger nasi, the ventral depression being the sulcus olfactorius 

 which leads to the olfactory region in the superior and dorsal part of the nasal fossa. 

 while the area inferior and dorsal to the agger is the atrium of the middle meatus. 

 This is bounded dorsally by the ventral vertical border of the middle nasal concha 

 (middle turbinate bone), beneath which it is continued into the middle meatus. On 

 the dorsal part of the lateral wall are the superior, middle, and inferior concha' 

 (turbinate bones), covering respectively the superior, middle, and inferior meat- 

 uses. The superior concha is occasionally divided into two or three parts, and pos- 

 terior and superior to it is a depression, the spheno-ethmoidal recess, which loads 

 to the opening into the sphenoidal sinus. 



The superior meatus is the smallest of the three. It has but a single opening, 



Fio. 769. THE LEFT WALL op TIIK X\-u. (\\ITY SHOWING THE CONCH.*: AND MEATUSES, 



WITH THE Ol'EMNCiS IN DOTTED Ot "II. INK. 



Orifice of mlddla ethmoidal cells 



SUPERIOR CONCHA 

 Orifice of the posterior ethmoidal cells 



Orifice of the spheuoidal sinus 

 Sphenoidal sinus 



Orifice of frontal sinus 



UPPER ORIFICE OF HUSO- 

 LACHRYMAL DUCT 



ORIFICE OF TUBA AUOITIVA 



MIDDLE CONCHA 



LOWER ORIFICE OF NA80- 

 LACHRYMUL DUCT 



INFERIOR CONCHA 



ORIFICE OF THE MAXILLARY ORIFICE OF INFUHDIBULUM 

 SINUS 



which leads into the posterior ethmoidal cells. The spheno-palatine foramen, which 

 communicates with the meatus in the dry skull, is entirely covered up by mucous 

 membrane. 



The middle meatus is a much larger passage. Upon its lateral wall is a rounded 

 eminence, the ethmoidal bulla, caused by the middle ethmoidal cells and perforated 

 by the opening into them. Ventral and inferior to this is a deep curved groove, the 

 hiatus semilunaris, which is continued superiorly by the infundibulum into tin- 

 frontal sinus. It also receives the openings of the anterior ethmoidal cells and the 

 maxillary sinus (antrum). Posterior to the semilunar hiatus an accessory opening 

 into the maxillary sinus is often seen. 



The inferior meatus is the lousiest of the three. Ventrally. just inferior to the 

 attachment of the inferior concha (turbinate bone), is the slit-like opening of the 

 naso-lachrymal (nasal) duct, around the opening of which the mucous membrajie 

 forms a valve, the plica lachrymalis (Ilasneri). 



The common meatus is the space between the nasal conclw and the septum, 

 and extends from the floor to the roof of the nasal fossa. The dorsal portion of the 



