310 MAMMALIAN ANATOMY 



FIG. 238. 



Attachment to Cribriform Plate. 



Seventh Inner Scroll, 6. 



Opposite Upper Part of 

 Seventh Piece. 



SIXTH PIECE OF LATERAL ETHMOID, INNER SURFACE. 



The above description may be regarded as that of the usual form 

 and arrangement of these pieces, but they are subject to variations, 



FIG. 239. 



Attachment to Cribriform Plate. 

 Twelfth Outer Scroll, jJg K^~ Thirteenth Outer Scroll, 7". 



Partition, ~ . 

 SEVENTH PIECE OF LATERAL ETHMOID, OUTER SURFACE. 



especially in the extent to which the outer edges of the partitions are 

 expanded for attachment to the walls of the nasal chambers. In some 



FIG. 240. 



Attachment to Cribriform Plate. 



Large Eighth Inner Scroll, 7, ' ^ ^ "^^&BT3k 



Entering Sphenoidal Sinus. \J ^H^Opposite law* Part of Sixth 



SEVENTH PIECE OF LATERAL ETHMOID, INNER SURFACE. 



cases so great is this expansion that the scrolls are scarcely visible on 

 the external surface. 



THE MESETHMOID. 



The mesethmoid is a thin and square sheet, placed vertically and 

 longitudinally between the lateral ethmoids (Fig. 242) and fastened 

 by its emarginate posterior edge to the anterior surface of the cribri- 

 form plate (Fig. 241). It is nearly as long, but not as high, as the 

 lateral ethmoids, leaving exposed the two inner upper scrolls, which, 

 however, are separated by the contiguous median plates of the frontals 

 extending downward. 



The straight superior border, which is directed downward in front, 

 is attached behind to the lower edge of these frontal plates, and in 



