220 



THE SKELETON, 



face, excepting the malar and lower jaw. Each cavity is bounded by a roof, a 

 floor, an inner and an outer wall. 



The upper wall, or roof (Fig. 176), is formed in front by the nasal bones and 

 groove lateral to the nasal spine of the frontal ; this part is directed downward 

 and forward; in the middle, by the cribriform plate of the ethmoid, which is hori- 

 zontal ; and behind, by the under surface of the body of the sphenoid, sphenoidal 

 process of the palate bone, and ala of the vomer, which are directed downward 

 and backward. This surface presents, from before backward, the internal aspect 

 of the nasal bones ; on their outer side, the suture formed between the nasal bone 

 and the nasal process of the superior maxillary ; on their inner side, the elevated 

 crest which receives the nasal spine of the frontal and the perpendicular plate of 

 the ethmoid, and articulates with its fellow of the opposite side ; whilst the surface 



Roof. 



Nasal bone, 



Nasal spine of frontal bone. 

 Horizontal plate of ethmoid. 

 Sphenoid. 



Probe passed through 

 naso-lachrymal canal. 



-Bristle passed through 

 infundibulum. 



Outer Wall. 



-Nasal proc. of sup. max. 

 'Lachrymal, 



'Ethmoid. 



Unciform process of ethmoid. 

 Inferior turbinated. 

 Palate. 



Superior meat us. 

 Middle meatus. 

 Inferior meatus. 



Floor. 



Anterior nasal spine. 

 Palate proc. of sup. max. 

 Palate process of palate. 



Posterior nasal spins.' 

 Anterior palatine canal. - 



FIG. 176. Roof, floor, and outer wall of left nasal fossa. 



of the bones is perforated by a few small vascular apertures, and presents the 

 longitudinal groove for the nasal nerve ; farther back is the transverse suture, 

 connecting the frontal with the nasal in front, and the ethmoid behind, the 

 olfactory foramina and nasal slit on the under surface of the cribriform plate, and 

 the suture between it and the sphenoid behind : quite posteriorly are seen the 

 sphenoidal turbinated bones, the orifices of the sphenoidal sinuses, and the 

 articulation of the alse of the vomer with the under surface of the body of the 

 sphenoid. 



The floor is flattened from before backward, concave from side to side, and 

 wider in the middle than at either extremity. It is formed in front by the palate 

 process of the superior maxillary ; behind, by the palate process of the palate bone. 

 This surface presents, from before backward, the anterior nasal spine ; behind 

 this, the upper orifices of the anterior palatine canal ; internally, the elevated crest 

 which articulates with the vomer ; and behind, the suture between the palate and 

 superior maxillary bones, and the posterior nasal spine. 



The inner wall, or septum (Fig. 177), is a thin vertical partition which sepa- 

 rates the nasal fossae from one another ; it is occasionally perforated, so that the 



