THE ANTERIOR REGION OF THE SKULL. 



115 



illary and palate bones. The circumference, or base, of the orbit, quadrilateral 

 in form, is bounded above by the supraorbital ridge ; below, by the anterior border 

 of the orbital plate of the malar and superior maxillary bones ; externally, by the 

 external angular process of the frontal and malar bones ; internally, by the internal 

 angular process of the frontal and the nasal process of the superior maxillary. 

 The circumference is marked by three sutures, the fronto-maxillary internally, the 

 fronto-malar externally, and the malo-maxillary below ; it contributes to the for- 

 mation of the lachrymal groove, and presents, above, the supraorbital notch (or 

 foramen), for the passage of the supraorbital vessels and nerve. The apex, situated 

 at the back of the orbit, corresponds to the optic foramen, 1 a short, circular canal 

 which transmits the optic nerve and ophthalmic artery. It will thus be seen that 

 there are nine openings communicating with each orbit viz. the optic foramen, 

 sphenoidal fissure, spheno-maxillary fissure, supraorbital foramen, infraorbital canal, 

 anterior and posterior ethmoidal foramina, malar foramina, and canal for the nasal 

 duct. 



The Nasal Fossae. 



The Nasal Fossas are two large, irregular cavities situated on either side of the 

 middle line of the face, extending from the base of the cranium to the roof of the 

 mouth, and separated from each other by a thin vertical septum. They communi- 

 cate by two large apertures, the anterior nares, with the front of the face, and by 

 the two posterior nares with the naso-pharynx behind. These fossae are much 



Roof. 



Nasal bone. 



Nasal spine of frontal bone. 

 Horizontal plate of ethmoid. 

 Sphenoid. 



II Probe passed through 

 fj naso-lachrymal canal. 



Bristle passed through 

 infundibulum. 



Outer Wall. 



Nasal proc. of sup. max. 

 Lachrymal. 

 Ethmoid. 



Unciform process of ethmoid. 

 Inferior turbinated. 

 Palate. 



Superior meatus. 

 Middle meatus. 

 Inferior meatus. 



Floor. ^ 



Anterior nasal spine. 

 Palate proc. of sup. max. 

 Palate process of palate. 



Posterior nasal spim. 

 Anterior palatine canal. 



FIG. 76. Roof, floor, and outer wall of left nasal fossa. 



narrower above than below, and in the middle than at the anterior or posterior 

 openings ; their depth, which is considerable, is much greater in the middle than 

 at either extremity. Each nasal fossa communicates with four sinuses, the frontal 

 above, the sphenoidal behind, and the maxillary and ethmoidal on the outer Avail. 



1 Quain, Testnt, and others give the apex of the orbit as corresponding with the inner end of the 

 sphenoidal fissure. It seems better, however, to adopt the statement in the text, since the muscles 

 of the eyeball take origin around the optic foramen, and diverge from it to the globe of the eye. 



