THE SKULL AS A WHOLE 



103 



eluding the spheno-palatine foramen six foramina open into the fossa. Of these, three are on 

 the posterior wall: enumerated from without inward, and from above downward, they are the 

 foramen rotundum, the pterygoid (Vidian) canal, and the pharyngeal (pterygo-palatine) 

 canal. The apex of the pyramid leads below into the pterygo-palatine canal and the accessory 

 palatine canals which branch from it; and anteriorly is the orifice of the infra-orbital canal. 

 The fossa contains the spheno-palatine ganglion, the maxillary nerve, and the terminal part of 

 the internal maxillary artery, and the various foramina and canals in relation with the fossa 

 serve for the transmission of the numerous branches which these vessels and nerves give off. 



Fig. 128. — A Section of the Skull showing the Medial Wall of the Orbit, the Medial 

 Wall of the Antrum, and the Pterygo-palatine Fossa. 



Frontal sinus 



Nasal bone 



Frontal process of maxilla 

 Lacrimal 



Lacrimal canal 



Orifice of antrum 



Inferior nasal concha 



Palate bone 



Anterior nasal spine 



Anterior ethmoid canal 

 Posterior ethmoid canal 



Optic foramen 



Lamina papyracea of ethmoid 



Spheno-palatine foramen 



Pterygoid canal, leading into the 



pterygo-palatine fossa 

 Sphenoid 



Lateral pterygoid plate 



Palate bone 



(4) Inferior Region or External Base of Skull 



The external base of the skull {norma hasilaris) (figs. 130, 131) extends from 

 the incisor teeth to the occipital protuberance, and is bounded on each side by 

 the alveolar arch, the zj^gomatic, the zygoma, the temporal, and the superior 

 nuchal line of the occipital bone. It is very uneven and, excluding the lower 

 jaw, divisible into three portions: (a) anterior, (b) middle or subcranial, and (c) 

 posterior or suboccipital. 



Fig. 129. — Hard Palate of a Child Five Years Old. 



Gubernacular canal 



Palate bone 



Incisive fossa 

 Incisive suture 



Palate process of maxilla 



r /■ 'vi^-— ^ —A - Greater palatine foramen 

 - -».- >r^-— -V^^ Lesser palatine foramen 



(a) The anterior division consists of the hard palate, the alveolar arch, and 

 the choanse (posterior nares). 



When the skull is inverted, the hard palate stands at a higher level than the 

 rest, and is bounded anteriorly and laterally by the alveolar ridges containing the 

 teeth. The bones appearing in the intermediate space are the premaxillary and 

 palatine portions of the maxillae and the horizontal parts of the palate bones. 



