NASAL FOSSAE. 187 



the former transmitting the anterior ethmoidal artery and nasal nerve, the latter 

 the posterior ethmoidal artery and vein. The inferior external angle, formed by 

 the junction of the outer wall or floor, presents the spheno-maxillary fissure, 

 which transmits the infraorbital vessels and nerve, and the ascending branches 

 from the spheno-palatine ganglion. The inferior internal angle is formed by 

 the union of the lachrymal and os planum of the ethmoid, with the superior 

 maxillary and palate bones. The circumference, or base, of the orbit, quadri- 

 lateral in form, is bounded above by the supraorbital arch ; below, by the 

 anterior border of the orbital plate of the malar, superior maxillary, and 

 lachrymal bones; externally, by the external angular process of the frontal and 

 the malar bone ; 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 formation of the lachrymal 

 groove, and presents above, the supraorbital notch (or foramen), for the passage 

 of the supraorbital artery, veins and nerve. The apex, situated at the back of 

 the orbit, corresponds to the optic foramen, a short circular canal, which trans- 

 mits the optic nerve and ophthalmic artery. It will thus be seen that there are 

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

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

 anterior and posterior ethmoidal foramina, malar foramina, and lachrymal canal. 



THE NASAL FOSSAE. 



The Nasal Fossse are two large irregular cavities, situated in 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 communicate 

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

 the pharynx behind by two posterior nares. These fossae are much 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. Bach nasal fossa communicates with four sinuses, the frontal above, 

 the sphenoidal behind, and the maxillary and ethmoidal on either side. Each 

 fossa also communicates with four cavities : with the orbit by the lachrymal 

 canal, with the mouth by the anterior palatine canal, with the cranium by the 

 olfactory foramina, and with the spheno-maxillary fossa by the spheno-palatine 

 foramen; and they occasionally communicate with each other by an aperture 

 in the septum. The bones entering into their formation are fourteen in num- 

 ber: three of the cranium, the frontal, sphenoid, the ethmoid, and all the bones 

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

 roof, an inner and an outer wall. 



The upper wall, or roof (Fig. 133), is long, narrow, and concave from before 

 backwards ; it is formed in front by the nasal bones and nasal spine of the 

 frontal, which are directed downwards and forwards; in the middle, by the 

 cribriform lamella of the ethmoid, which is horizontal ; and behind, by the 

 under surface of the body of the sphenoid, and sphenoidal turbinated bones, 

 which are directed downwards and backwards. This surface presents, from" 

 before backwards, the internal aspect of the nasal bones ; on the 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 of the bones is perforated 

 by a few small vascular apertures, and presents the longitudinal groove for the 

 nasal nerve : further 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 



