THE SKULL THE CRANIUM 299 



combined tenth and eleventh and combined twelfth and thirteenth 

 outer scrolls. The plates or folds which form the anterior end of the 

 lateral ethmoid are joined to this area by a narrow stalk. The ex- 

 panded lateral posterior part of the vomer is attached to the flatter 

 bands along the outer borders of the inferior surface, and is under- 

 lapped by the sphenoidal processes of the palatine bones. In front of 

 this union and on each side of the vomer spaces are left between the 

 lower surface of the ethmoid above and the palatine plates of the 

 maxillary and palatines which lie below and form the floor of the 

 nasal chamber. These spaces, called the inferior meatuses, are canals 

 which open anteriorly at the anterior nares. Behind the attachment of 

 the vomer to the palatines they communicate with each other freely, and 

 their common posterior end opens into the pharynx at the posterior nares. 

 The internal or medial surface of the lateral ethmoid (Figs. 218, 

 219) has the same shape as the outer surface. It is much flatter, how- 

 ever, and not divided into two distinct parts by a vertical fissure. The 

 scrolls which compose it are larger and simpler, because, with one ex- 

 ception, every one is the inner surface of two united outer scrolls. An 

 area occupied by the third, fourth, fifth, and sixth scroll is depressed 

 below the rest of the surface. This area is wider behind at the cribri- 

 form plate and narrower in front where it cuts through the superior 

 border behind the anterior angle. This depression forms with the 

 side of the mesethmoid a passage known as the superior meatus of 

 the nose. There are eight scrolls on this surface. The upper one 

 (Fig. 219, 1') is long and curved and larger behind than in front ; the 

 anterior end turns outward to join the end of the partition behind it 

 and the next outer scroll. The second scroll (m') is shorter ; its upper 

 convex surface lies on the concave lower surface of the first scroll, and 

 its lower straight border lies against a partition (m) which separates 

 it from the third scroll. This partition is slightly sinuate, and forms 

 the upper boundary of the depressed area already described ; its edge 

 is united with the lower edge of the median plate of the frontal, with 

 the outer edge of the posterior surface of the nasal, and, for a varying 

 extent behind, with the upper edge of the mesethmoid. Hence the 

 two upper scrolls are in fact shut off from the rest of the nasal 

 chamber. The third scroll (m") is very narrow behind, then widens 

 and maintains the same width for the rest of its extent. It runs down- 

 ward and forward ; for the first half or more it is concave from above 



