328 



MAMMALIAN ANATOMY 



bounds the spheno-palatine foramen above joins the lateral edge of 

 the vomer and the lower edge of the lateral ethmoid. 



The sphenoidal process of the vertical plate (Figs. 253, 255, 256, 

 257) is in the form of a thin oblong strip of bone which runs backward 

 from the posterior lower border of the ethmoidal process. It slopes 



FIG. 256. 



Frontal.\ 



Nasal. 



Upper Anterior part of 

 Ethmo-turbinal. ' 



Maxillo-iurbinal. 



Cut edge of Cribriform plate 

 of Ethmoid. 



Lower Posterior part 

 of Ethmo-turbinal 

 in Sinus. 



Vertical LongitntU- 



v i n Sphenoi- 



-al Sinus. 



Premaxillary. 



Horizontal plates 

 of Maxillary 

 and Palatine. 



Vertical 

 plate of 

 Palatine. 



Pterygoid. 



Vomer. 



RIGHT NASAL CHAMBER, SIDE VIEW FROM WITHIN. 



inward and upward, and, with the exception of a small anterior part 

 behind the spheno-palatine foramen, forms with the horizontal plate 

 a smaller angle than does the ethmoidal part. It is twice as long as 

 high. The lower border is rounded and bounds laterally the posterior 

 uares. The upper border is wide, rough, and bevelled. Its inner part 

 is continued forward as far as the spheno-palatine foramen ; it overlaps 

 the edge of the vomer and articulates also with the presphenoid. Its 

 outer part joins the upper border of the ethmoidal process and over- 

 laps the orbitosphenoid. The posterior border is serrated and joins 

 the pterygoid. 



The outer surface is slightly concave in both directions, and faces 

 outward and upward. It gives origin through most of its extent to 

 the external pterygoid muscle. 



