THE SKULL THE CEANIUM 



297 



narrow. For the posterior half or more it is formed by the upper 

 rounded surface of the upper scroll (Fig. 216, 1'), and on the outside 



FIG. 215. 



Mesethmoid or Perpendicular Plate 

 of Ethmoid. 



With Maxillary. J 



/ / 



Mesethmoid, with Cartilaginous Nasal Septum. 



Part of Left Lateral Ethmoiil entering opening 



into Frontal Sin UK. 

 Upper Part, contained in Nasal Cavity. 



Left Lateral Ethmoid, with Frontal. 



Lower Part of Left Lateral Ethmoid, near 

 iHaxillo-turbinal. 



Vomer. 



FIG. 216. 



THE ETHMOID BONE, ANTERIOR ASPECT. 



of the scroll by the sharp edge of the first partition (1), continued 

 in front as the upper edge of the posterior border of the cleft on the 

 external surface. The parti- 

 tion is fastened to a ridge on 

 the roof of the so-called ex- 

 ternal frontal sinus which con- 

 tains the scroll. Where the 

 scroll ends in front, separated 

 from it by the obliquely di- 

 rected anterior end of the 

 edge of the single partition 

 on the inner surface (m), is 

 the beginning, on a lower 

 level, of the plate-like forward 

 extension of the third scroll 

 on the inner surface (m"), 

 which forms the rest of the 

 surface and covers the upper surface of the small anterior scrolls. 



The anterior surface of the lateral ethmoid is not sharply defined 

 from the outer and lower surfaces. It is triangular ; the apex of the 



it cleft 

 ft plate 



KTHMOID, SUPERIOR SURFACE. PARTS NUMBERED. 



