THE SKULL AS A WHOLE 



107 



Behind the hard palate are the choanae (posterior nares), separated from each other by the 

 vomer. Each is bounded laterally by the medial pterygoid plate; below by the horizontal 

 plate of the palate bone; above by the under surface of the body of the sphenoid, with the ala 

 of the vomer and a portion of the sphenoidal process of the palate bone. 



Lateral to the choanae there is on each side a vertical fossa lying between the pterygoid 

 plates. It extends upward to the under surface of the great wings of the sphenoid; it is com- 

 pleted anteriorly by the coalescence of the pterygoid plates and below by the pyramidal process 

 of the palate bone. It contains the following points of interest: — 



An elongated furrow, the scaphoid fossa, for the tensor veli palatini muscle and the carti- 

 lage of the Eustachian tube. 



The general cavity of the pterygoid fossa which lodges the tensor veli palatini and internal 

 pterygoid muscles. 



Fig. 133. — The Skull. (Norma facialis.) 



Ophryon- 

 Superciliary arch 

 Glabella 



Nasion 



Nasal (piriform) 

 aperture 



Subnasal point 

 Canine fossa 



Canine eminence 

 Alveolar point 



Frequently there is a notch in the lateral pterygoid plate close beside the foramen ovale. 

 The posterior termination of the pterygoid (Vidian) canal. 



If a line be drawn across the base of the skull from one preglenoid tubercle to 

 the other, it will fall immediately behind the lateral pterj-goid plate and bisect 

 the foramen spinosum on each side. A second transverse line, drawn across the 

 opisthion or posterior margin of the foramen magnum, will fall behind the 

 mastoid processes. The space between these arbitrary lines may be called the 

 subcranial region; that behind the second line, the suboccipital region. 



(b) The subcranial region is separated from the infratemporal fossa by a line 

 drawn from the posterior margin of the lateral pterygoid plate to the spine of the 



