CAVITIES OF THE NOSE. 123 



bounded by the internal surface of the os nan of its respective 

 side ; and posterior to it, by the anterior surface of the body of 

 the sphenoid bone. These anterior and posterior surfaces form 

 obtuse angles with the upper surface of the nose, and^are im- 

 mediately above the openings called anterior and posterior nares. 

 The anterior surface partakes of the figure of the os nasi ; the 

 upper surface has the perforations of the cribriform plate ; the 

 posterior surface has an opening, equal in diameter to a small 

 quill, that leads into the sphenoid cell, and is also broader than 

 the anterior or superior surface. 



The internal surface, formed by the septum of the nose, 

 which is composed of the vomer, the nasal plate of the ethmoid, 

 and the cartilaginous plate, is flat, but rather inclined to one side or 

 the other, so as to make a difference in the size of the nasal cavities. 

 Fig. 29.* The external surface is very 



irregular; it is formed by the 

 cellular portions of the ethmoid; 

 by a small portion of the os 

 unguis ; by the upper maxillary 

 bone ; the os turbinatum infe- 

 rius ; the os palati ; and the 

 internal pterygoid process of 

 the 05 sphenoides. The upper 

 part of this surface is formed 

 by the internal surface of the 

 cellular portions of the ethmoid, 



* Fig. 29. A longitudinal section of the nasal fossa (taken from Wilson) 

 made to the right side of the vomer, and the bony septum removed in order to 

 exhibit the external wall of the left nasal fossa. 1. Os frontis 2. Os nasi. 3. 

 The cristagalli process of the ethmoid. The groove between fig. 1 &c 3, is the 

 lateral boundary of the foramen caecum. 4. The cribriform plate of the ethmoid. 

 5. Part of the sphenoidal cells. 6. The basilar portion of the sphenoid bone. 

 Bones 2, 4, & 5. form the superior boundary of the nasal fossa. 7, 7. The 

 articulating surface of the palatine process of the superior maxillary bone. 

 The groove between 7, 7. is the lateral half of the incisive canal, and the dark 

 aperture in the groove the inferior termination of the left naso palatine canal. 

 8. The nasal spine. 9. The palatine process of the palate bone. a. The superior 

 turbinated bone marked by grooves and apertures for filaments of the olfactory 

 nerve, b. The superior meatus. c. A probe passed into the posterior ethmoidal 

 cells, d. The opening of the sphenoidal cells into the superior meatus. e. The 

 spheno-palatine foramen. /. The middle turbinated bone, g, g. The middle 

 meatus. h. A probe passed into the infundibular canal, leading from the frontal 



