56 BASE OF THE SKULL. 



several small fossae for the Pacchionian bodies, and further outwards 

 digital fossse corresponding with the convexities of the convolutions 

 and numerous ramified markings for lodging the branches of the 

 arteria meningea media. 



The LATERAL REGION of the skull is divisible into three portions ; 

 temporal, mastoid, and zygomatic. 



The temporal portion, or temporal fossa, is bounded above and 

 behind by the temporal ridge, in front by the external angular process 

 of the frontal bone and by the malar bone, and below by the zygoma. 

 It is formed by part of the frontal, great wing of the sphenoid, parietal, 

 squamous portion of the temporal, malar bone and zygoma, and lodges 

 the temporal muscle with the deep temporal arteries and nerves. 



The mastoid portion is rough, for the attachment of muscles. Upon 

 its posterior part is the mastoid foramen, and below, the mastoid pro- 

 cess. In front of the mastoid process is the external auditory fora- 

 men, surrounded by the external auditory process ; and in front of this 

 foramen the glenoid cavity, bounded above by the middle root of the 

 zygoma and in front by its tubercle. 



The zygomatic portion, or fossa, is the irregular cavity below the 

 zygoma, bounded in front by the superior maxillary bone, inter- 

 nally by the external pterygoid plate, above by part of the great 

 wing of the sphenoid and squamous portion of the temporal bone, and 

 by the temporal fossa, and externally by the zygomatic arch and ramus 

 of the lower jaw. It contains the external pterygoid, with part of the 

 temporal and internal pterygoid muscle, and the internal maxillary 

 artery and inferior maxillary nerve, with their branches. At the 

 bottom of the zygomatic fossa are two fissures, the spheno- maxillary 

 and the pterygo-maxillary. The spheno-mairillary fissure is horizontal 

 in direction, opens into the orbit, and is situated between the great 

 ala of the sphenoid and the superior maxillary bone. It is completed 

 externally by the malar bone. The pterygo-maxillary fissure is verti- 

 cal, and descends at right angles from the extremity of the preceding. 

 It is situated between the pterygoid process and the tuberosity of the 

 superior maxillary bone, and transmits the internal maxillary artery. 

 At the angle of junction of these two fissures is a small cavity, the 

 splieno-maxillary fossa, bounded by the sphenoid, palate, and superior 

 maxillary bones, in which are seen the openings of five foramina, 

 the foramen rotundum, spheno-palatine, pterygo-palatine, posterior 

 palatine, and Vidian. It lodges MeckePs ganglion and the termina- 

 tion of the internal maxillary artery. 



The BASE OF THE SKULL presents an internal or cerebral, and 

 an external or basilar surface. 



The cerebral surface is divisible into three parts, which are named 

 the anterior, middle, and posterior fossa of the base of the cranium. 

 The anterior fossa is somewhat convex on each side, where it cor- 

 responds with the roofs of the orbits ; and concave in the middle, in 

 the situation of the ethmoid bone and the anterior part of the body of 

 the sphenoid. The latter and the lesser wings constitute its posterior 



