102 OSTEOLOGY. 



part of the temporal bone, the orifice of the mastoid foramen may be seen ; and, 

 just previous to its termination, it has opening into it the posterior condyloid 

 foramen. 



The External Surface of the base of the skull (fig. 63) is extremely irregular. 

 It is bounded in front by the incisor teeth in the upper jaws ; behind, by the 

 superior curved lines of the occipital bone ; and laterally, by the alveolar arch, the 

 lower border of the malar bone, the zygoma, and an imaginary line, extending 

 from the zygoma to the mastoid process and extremity of the superior curved line 

 of the occiput. It is formed by the palate processes of the two superior maxillary 

 and palate bones, the vomer, the pterygoid, under surface of the great wing, 

 spinous process and part of the body of the sphenoid, the under' surface of the 

 squamous, mastoid, and petrous ' portions of the temporal, and occipital bones. 

 The anterior part of the base of the skull is raised above the level of the rest of 

 this surface (when the skull is turned over for the purpose of examination), 

 surrounded by the alveolar process, which is thicker behind than in front, and 

 excavated by sixteen depressions for lodging the teeth of the upper jaw ; they 

 vary in depth and size according to the teeth they contain. Immediately behind 

 the incisor teeth is the anterior palatine fossa. At the bottom of this fossa may 

 usually be seen four apertures, two placed laterally, which open above, one in the 

 floor of each nostril, and transmit the anterior palatine vessels, and two in 

 the median line of the intermaxillary suture, one in front of the other, the most 

 anterior one transmitting the left, and the posterior one (the larger) the right 

 naso-palatine nerve. These two latter canals are sometimes wanting, or they may 

 join to form a single one, or one of them may open into one of the lateral canals 

 above referred to. The palatine vault is concave, uneven, perforated by numerous 

 foramina, marked by depressions for the palatal glands, and crossed by a crucial 

 suture, which indicates the point of junction of the four bones of which it is com- 

 posed. One or two small foramina, seen in the alveolar margin behind the incisor 

 teeth, occasionally seen in the adult, almost constant in young subjects, are called the 

 incisive foramina ; they transmit nerves and vessels to the incisor teeth. At each 

 posterior angle of the bard palate is the posterior palatine foramen, for the trans- 

 mission of the posterior palatine vessels and anterior palatine nerve, and running 

 forwards and inwards from it a groove, which lodges the same vessels and nerve. 

 Behind the posterior palatine foramen is the tuberosity of the palate bone, per- 

 forated by one or more accessory posterior- palatine canals, and marked by the 

 commencement of a ridge, which runs transversely inwards, and serves for the 

 attachment of the tendinous expansion of the Tensor palati. muscle. Projecting 

 backwards from the centre of the posterior border of the hard palate is the pos- 

 terior nasal spine, for the attachment of the Azygos uvula?. Behind and above 

 the hard palate is the posterior aperture of the nares, divided into two parts by 

 the vomer, bounded above by the body of the sphenoid, below by the horizontal 

 plate of the palate bone, and laterally by the pterygoid processes of the sphenoid. 

 Each aperture measures about an inch in the vertical, and half an inch in the 

 transverse direction. At the base of the vomer may be seen the expanded al 

 of this bone, receiving between them the rostrum of the sphenoid. Near the 

 lateral margins of the vomer, at the root of the pterygoid processes, are the 

 pterygo-palatine canals. The pterygoid process, which bounds the posterior 

 nares on each side, presents near its base the pterygoid or Vidian canal, for the 

 Vidian nerve and artery. Each process consists of two plates, which bifurcate 

 at the extremity to receive the tuberosity of the palate bone, and are separated 

 behind by the pterygoid fossa, which lodges the Internal pterygoid muscle. The 

 internal plate is long and narrow, presenting on the outer side of its base the 

 scaphoid fossa, for the origin of the Tensor palati muscle, and at its extremity 

 the hamular process, around which the tendon of this muscle turns. The external 

 pterygoid plate is broad, forms the inner boundary of the zygomatic fossa, and 

 affords attachment to the External pterygoid muscle. 



