BONES OF THE SKULL. 



mass of the ethmoid, vertical plate of the palate, inferior tur- 

 binate, and internal pterygoid plate of the sphenoid. The an- 

 terior opening (anterior naris) of each fossa is half heart-shaped 

 and looks somewhat downward; the posterior opening (pos- 

 terior naris) is smaller, rhomboidal, and also looks somewhat 

 downward. [173] 



On the outer wall are seen three longitudinal and shell-like 

 laminae, of which the upper two are processes (superior, and 

 middle turbinated) of the ethmoid while the lower is the infe- 

 rior turbinated bone; they roof over the channels on the wall, 

 respectively the superior, middle, and inferior meatus. The 

 inferior meatus receives the canal for the nasal duct, anteriorly 

 and high up ; in the front of its floor, near the midline, is a fora- 

 men (anterior palatine canal) . The middle meatus slopes down- 

 ward and backward ; from it a passage (inf undibulum) ascends 

 to the frontal sinus and some ethmoidal cells; near its centre 

 is an opening into the antrum of Highmore. The superior 

 meatus receives the openings of the posterior ethmoidal cells; 

 it presents a foramen (spheno-palatine) posteriorly. [168] 



The nasal septum is cartilaginous in front and bony behind. 

 The bony part consists chiefly of the vomer below and the 

 vertical plate of the ethmoid above; and partly of the nasal 

 crests of the superior maxillae and palate bones below, and 

 those of the nasal bones, the nasal process of the frontal, and 

 the ethmoidal crest and rostrum of the sphenoid above. It is 

 usually deflected to one side. [173] 



The sphenoidal sinus is in the body of the sphenoid and is 

 divided by a mesial septum ; each part opens into a depression 

 (spheno-ethmoidal recess) in the roof of the nasal fossa; it is 

 closed anteriorly by a hollow and three-sided pyramidal bone 

 (sphenoidal turbinal). The ethmoidal sinuses lie between the 

 orbits and the sides of the upper parts of the nasal fossae. A 

 sinus in the orbital process of the palate bone opens into either 

 the sphenoidal sinus or some of the posterior ethmoidal si- 

 nuses. The maxillary sinus (antrum of Highmore) is pyram- 

 2 [17] 



