NASAL FOSSJE. 109 



two foramina, the anterior and posterior ethmoidal, 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 and floor, presents the spheno-maxillary fissure, which transmits the infra- 

 orbital vessels and nerve, and the ascending branches from the spheno-palatine 

 ganglion. The inferior internal angle is formed by the union of the lachrymal bone 

 and os planum of the ethmoid, with the superior maxillary and palate bones. The 

 circumference or base of the orbit, quadrilateral in form, is bounded above by the 

 supra-orbital 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 supra-orbital notch 

 or foramen, for the passage of the supra-orbital artery, veins, and nerve. The 

 apex, situated at the back of the orbit, corresponds to the optic foramen, 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 lacerum anterius, spheno-maxillary fissure, supra-orbital fora- 

 men, infra-orbital 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 the 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. 

 Each nasal fossa communicates with four sinuses, the frontal above, the sphenoidal 

 behind, and the maxillary and ethmoidal on either side. Each fossa also commu- 

 nicates 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 occa- 

 sionally communicate with each other by an aperture in the septum. The bones 

 entering into their formation are fourteen in number : three of the cranium, the 

 frontal, sphenoid, and ethmoid, and all the bones of the 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. 66) is long, narrow, and concave from before back- 

 wards ; 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 their outer side, the suture formed between 

 the nasal, with 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 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 ulae of the 

 vorner with the under surface of the body of the sphenoid. 



