THE SKULL THE CEANIUM 



295 



minate anteriorly and to the cribriform plate and to the investing walls 

 of the nasal chamber produces cavities which are sometimes called the 

 ethmoidal cells. Every cavity, except as noted, contains two scrolls. 



The scrolls and partitions are not independent structures, but are 

 continuous within, the partitions being merely the outer unrolled edges 

 of the scrolls. Although there is considerable diversity in the ar- 

 rangement of these parts, it would seem that the inner edge of each 



Posterior Wall of Right Frontal Sinus. \ 



FIG. 213. 



Frontals. 



s -Postorbital Process. 



Orbitoxphcnoid. 



Part of Vertical Plate A_ 



oj Palatine. 



Alisphenoid. 



Orbitosphenoid and 

 Presphenoid. 



Cribriform Plate. 

 Line of Attachment of Lower Eth- 

 moidal Scroll to Orbitosphenoid. 

 Septum between Sphenoidal 

 Sinuses. 



Lower Ethmoidal Scroll. 



^H^^H Pterygoid. 



THE SKULL. TRANSVERSE SECTION JUST BEHIND POSTERIOR NARES, SEEN FROM IN FRONT. 



partition splits and rolls up to form the scrolls which lie on either side 

 of it. Many of these scrolls appear on the inner or medial surface 

 of the lateral ethmoid, which surface they largely form, but they are 

 considerably disturbed by pressure. The third and fourth scrolls, 

 counting from the upper border (Fig. 214, 2', 2"), do not appear on 

 the inner surface of the lateral ethmoid, as they rest in part on the 

 first and second scrolls (!', 1") and in part are covered by two addi- 

 tional scrolls, which are seen only on the inner surface (Fig. 219, m', 

 m"). The fifth and sixth scrolls (Fig. 214, 3', 3") likewise are seen 

 only on the external surface, owing to the expansion of the seventh 

 and eighth scrolls (4/ 4"). 



Notwithstanding distortion by pressure, it is possible to separate 

 this larger posterior part of the lateral ethmoid into eight little masses, 

 which may be detached from the posterior wall of the cleft in front and 



