THE BASE OF THE SKULL. 213 



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

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

 spiuous processes and part of the body of the sphenoid, the under surface of the 

 squamous. mastoid. and petrous portions of the temporal, and the under surface 

 of the occipital bone. 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. the cavities varying 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, the foramina 



^''//.""/i. which open above, one in the floor of each nostril, and transmit the 

 anterior branch of the posterior palatine vessels, and two in the median line in 

 the intermaxillary suture, the foramina, of Searpa, one in front of the other, the 

 anterior transmitting the left, and the posterior (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 palatine glands, and crossed by a crucial suture, 

 formed by the junction of the four bones of which it is composed. At the front 

 part of this surface a delicate linear suture may frequently be seen, marking off 

 the pre-maxillary portion of the bone. One or two small foramina in the alveolar 

 margin behind the incisor teeth, occasionally seen in the adult, almost constantly in 

 young subjects, are called the incisive foramina : they transmit nerves and vessels 

 to the incisor teeth. At each posterior angle of the hard palate is the posterior 

 palatine f"i-<i a" n. for the transmission of the posterior palatine vessels and large 

 descending palatine nerve; and running forward and inward from it a groove, for 

 the same vessels and nerve. Behind the posterior palatine foramen is the tuberosity 

 of the palite bone, perforated by one or more accessory posterior palatine canals, 

 and marked by the commencement of a ridge, which runs transversely inward, and 

 serves for the attachment of the tendinous expansion of the Tensor palati muscle. 

 Projecting backward from the centre of the posterior border of the hard ] alate is 

 the post- '/ spine, for the attachment of the Azygos uvulae. 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 and a quarter in the vertical and about 

 half an inch in the transverse direction. At the base of the vomer may be seen 

 the expanded alre of this bone, receiving between them the rostrum of the sphenoid. 

 Xear 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 

 A idian nerve and artery. Each process consists of two plates, which bifurcate at 

 the extremity to receive the tuberosity of the ] alate 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 ha mular 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 by 

 its outer surface to the External pterygoid muscle. 



Behind the nasal t<>ss;e in the middle line is the basilar surface of the occipital 

 bone, presenting in its centre the pharyngeal spine, for the attachment of the 

 Superior constrictor muscle of the pharynx, with depressions on each side for 

 the insertion of the Rectus capitis anticus major and minor. At the base of the 

 external pterygoid plate is the />/<///</ ovale ; behind this, the foramen spinosntn 

 and the prominent spinous process of the sphenoid, which gives attachment to the 

 internal lateral ligament of the lower jaw and the Tensor palati muscle. External 



