Skull and Hyoid 



245 



septun 



body of the maxilla and the vertical plate of the palate (applied to the maxilla) con- 

 stitute the outer wall so far as they go, and separate the nasal fossa from the antrum 

 of Highmore. But the nasal cavity extends higher than the jaw, and the outer wall 

 above the level of the maxilla must separate the nasal and orbital cavities. Look, 

 therefore, into the orbit and see how its inner wall is made (Fig. 195), and it can be seen 

 that the thin os planum of the ethmoid forms the largest part of it, but is deficient 

 in front, and here the lachrymal bone fills up the deficiency and lies between the os 

 planum and the nasal process of the maxilla. 



FIG. 194. Outer wall of left nasal fossa. i. With mucous membrane in position. 2. Mucous mem- 

 brane removed. Notice the flat inner surface of the mass of the labyrinth, from which the upper and 

 middle turbinals are suspended. 3. The free projections of the turbinals have been cut away, exposing 

 the outer wall in the lower part of the fossa, but showing only the inner wall of the mass of the labyrinth 

 in the upper portion of the fossa ; the lines of section of the turbinals is apparent. L. lachrymal ; 

 U, unciform process of ethmoid ; A . cut edge of inferior turbinate ; M, its maxillary process turned 

 down in the large antral opening, to articulate with its lower margin : the other processes are seen 

 running up to articulate with U and L respectively. 



We can say, then, that the upper part of the outer wall is made by the os planum, 

 lachrymal, and nasal process of maxilla, while the 

 lower and greater part is made by the body of the 

 maxilla and vertical plate of palate. The lachrymal 

 comes down for some distance internal to the 

 maxilla to separate the nasal cavity from the nasal 

 duct, and the uncinate process of the ethmoid also 

 comes down, behind the lachrymal, on the inner side 

 of the maxilla and closes in the front part of the 

 antral opening. Another element, a separate 

 inferior turbinate bone, is applied to the lower 

 division of the wall, and a part of this turns down 

 into the lower part of the antral opening and closes 

 this : behind this the inferior turbinate is fixed to 

 the vertical plate of the palate, and in front of the 

 position of the antral opening the attached border 

 of the inferior turbinate lies across the maxilla 

 nearly as far forward as the anterior nasal margin. 

 The line of the turbinate thus lies a little below the 

 uncinate process and the lachrymal, and it gives 

 short processes upwards to articulate with these 

 (and still further close in the antral opening), so 

 that these processes of the turbinate can be looked 

 on as entering into the composition of the outer 

 wall. 



(The third diagram in Fig. 194 will give some 

 idea of these arrangements on the outer wall : the 

 line of the attached part of the inferior turbinate, which has been cut away, is shown 

 at A, and its processes are seen joining the lachrymal (L.) and uncinate process (U.). 

 The maxillary process, turned down, is seen at M.) 



The anterior process of the inferior turbinal, by articulating with the lachrymal, 

 completes the inner wall of the nasal duct and separates it from the nose, so that its 

 lower opening must be below the level of the inferior turbinate. 



The upper and middle turbinate bones are part of the ethmoid. 



FIG. 195. Scheme of the position of 

 the lateral mass or labyrinth and 

 the arrangement of turbinals. 

 The inferior turbinate hangs from 

 the outer wall below the ethmoid, 

 but the others are parts of that 

 bone ; one is shown hanging from 

 the inner wall of the labyrinth. 

 The whole labyrinth forms a mass 

 in the upper part of the nose, so 

 that the plane of attachment of 

 the upper two turbinals is nearer 

 the septum than that of the inferior 

 turbinal, although the outer wall 

 of the nasal cavity is further from 

 the septum in the upper than in 

 the lower part. 



