116 THE SKELETON. 



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

 groove, 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 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. 76), is long, narrow, and horizontal in its centre, 

 but slopes downward at its anterior and posterior extremities ; it is formed in front 

 by the nasal bones and nasal spine of the frontal, which are 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 and sphe- 

 noidal turbinated bones, the ala of the vomer and the sphenoidal process of the 

 palate bone, 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 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 alas 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. 77), is a thin vertical partition which sepa- 

 rates the nasal fossae from each other; it is occasionally perforated, .so that the 

 fossre communicate, and it is frequently deflected considerably to one side. 1 It 

 is formed, in front, by the crest of the nasal bones and nasal spine of the frontal; 

 in the middle, by the perpendicular plate of the ethmoid ; behind, by the vomer 

 and rostrum of the sphenoid ; below, by the crests of the superior maxillary and 

 palate bones. It presents, in front, a large, triangular notch, which receives the 

 septal cartilage of the nose; and behind, the grooved edge of the vomer. Its 

 surface is marked by numerous vascular and nervous canals and the groove for 

 the naso-palatine nerve, and is traversed by sutures connecting the bones of which 

 it is formed. 



The outer wall (Fig. 76) is formed, in front, by the nasal process of the 

 superior maxillary and lachrymal bones; in the middle, by the ethmoid and 

 inner surface of the superior maxillary and inferior turbinated bones ; behind, 

 by the vertical plate of the palate bone and the internal pterygoid plate of the 

 sphenoid. This surface presents three irregular longitudinal' passages, or mea- 

 tmes, termed the superior, middle, and inferior meatuses of the nose. The 

 superior meatus, the smallest of the three, is situated at the upper and back part of 

 each nasal fossa, occupying the posterior third of the outer wall. It is situated 

 between the superior and middle turbinated bones, and has opening into it two 

 foramina, the sphefio-palatine at the back of its outer wall, and the posterior 

 ethmoidal cells at the front part of the outer wall. The sphenoidal sinus opens 



'See footnote, p. 78. 



