Bones of the Skull. 



21 



Processus alaris 

 Crista galli 



Lamina cribrosa 



Concha nasalis media Foramen ethmoidale anterius 

 Concha nasalis superior Lamina papyracea 



Recessus sphenoethmoid. Foramen ethmoi- 1 

 Concha nasalis suprema dale posterius \ 



Crista galli 



, Processus 

 alaris 



Concha nasalis inferior 



i 



Processus uncinatus 



From within. 



I Lamina 



perpendicularis 



Processus uncinatus 

 Concha nasalis media 



23 and 24. Right 

 ethmoidal labyrinth, 



labyrinthus ethmoidalis. 



From without. 



Each labyrinthus ethmoidalis (0. T. lateral mass of ethmoid) (see also Figs. 21, 22, 

 65, 66, 68, 70 and 72 75) is oblong and quadrangular in shape and is connected only above 

 and medianward with the lateral border of the lamina cribrosa. Inside it is divided by delicate 

 platelets of bone into the numerous cellulae ethm.oidales (ethmoid cells) lined by mucous mem- 

 brane. They communicate with one another and are closed completely by the wall of the 

 ethmoid bone only on the medial and lateral surface ; otherwise they project against neighboring 

 bones, or into them; thus in the isolated bone they partly open and become closed cavities 

 only by the attachment of adjacent bones; in front the pars nasalis oss. frontalis and proc. 

 frontalis maxillae, lateralward by the os lacrimale and corpus maxillae, behind by the proc. 

 orbitalis oss. palatini, corpus oss. sphenoidalis and conchae sphenoidales, above by the pars 

 orbitalis oss. frontalis; spread out on the latter surface of union are the foramen ethmoidale 

 anterius (for the a. ethmoid, ant. ; n. ethmoid, ant.) and the foramen ethmoidale poslerius 

 (for the a. ethmoid, post.; n. ethmoid, post., IT. orbit, gangl. sphenopalat.) (see also p. 17). 

 The lateral wall of the labyrinth, lamina papyracea (0. T. os planum), is oblong, quadrangular, 

 and unites in front with the os lacrimaJe, below with the corpus maxillae (sutura ethmoideo- 

 maxillaris), behind with the proc. orbital, oss. palat. (sutura palatoethmoidalis) and the corpus 

 oss. sphenoid, (sutura sphenoellimoidalis), above with the pars orbital, oss. front, (sutura 

 frontoethmoidalis). The medial wall is vertical, is very rough, and much perforated. Its an- 

 terior margin is attached to the posterior surface of the spina frontalis oss. frontalis, its posterior 

 border to the anterior surface of the concha sphenoidalis: the inferior thickened border 

 hangs down free, bends around somewhat lateralward, and thus forms the concha nasalis media 

 (middle turbinated bone): above this in the posterior part is a deep notch (meatus nasi superior , 

 upper nasal passage) and above this a similar, concha-like plate of bone, bent so as to be 

 convex medianward, the concha nasalis superior (superior turbinated bone) ; further backward 

 and upward lies usually still another turbinated bone, the concha nasalis suprema [Santorini], 

 separated from the preceding by a groove, the recessus sphenoethmoidalis. Lateralward from 

 the anterior extremity of the concha media, a sickle-shaped process, the processus uncinatus 

 (0. T. unciform process), directed backward, becomes separated from the inferior wall; at its 

 extremity it rolls around lateralward, and below or behind this place unites with the proc. 

 ethmoidalis conchae nasalis inferioris (see also Figs. 68 and 74). 



