BASE OF THE SKULL. 59 



ternally to the commencement of the internal jugular vein and in- 

 ternally to the eighth pair of nerves. Converging towards this fora- 

 men from behind is the deep groove for the lateral sinus, and from the 

 front the groove for the inferior petrosal sinus. 



Behind the foramen magnum is a longitudinal ridge, which gives 

 attachment to the falx cerebelli, and divides the two inferior fossae of 

 the occipital bone ; and above the ridge is the internal occipital pro- 

 tuberance and the transverse groove lodging the lateral sinus. 



The external surface of the base of the skull is extremely irregular. 

 From before backwards it is formed by the palate processes of the 

 superior maxillary and palate bones ; the vomer ; pterygoid, spinous 

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

 squamous, petrous, and mastoid portion of the temporals ; and by the 

 occipital bone. The palate processes of the superior maxillary and 

 palate bones constitute the hard palate, which is raised above the level 

 of the rest of the base, and is surrounded by the alveolar processes 

 containing the teeth of the upper jaw. At the anterior extremity of 

 the hard palate, and directly behind the front incisor teeth, is the 

 anterior palatine or incisive foramen, the termination of the anterior 

 palatine canal, which contains the naso-palatine ganglion, and trans- 

 mits the anterior palatine nerves. At the posterior angles of the 

 palate are the posterior palatine foramina, for the posterior palatine 

 nerves and arteries. Passing inwards from these foramina are the 

 transverse ridges to which are attached the expansions of the tensor 

 palati muscles, and at the middle line of the posterior border the palate 

 spine which gives origin to the azygos uvulae. The hard palate is 

 marked by a crucial suture, which distinguishes the four processes of 

 which it is composed. Behind, and above the hard palate, are the 

 posterior nares, separated by the vomer, and bounded on each side by 

 the pterygoid processes. At the base of the pterygoid processes are 

 the pterygo-palatine canals. The internal pterygoid plate is long and 

 narrow, terminated at its apex by the hamular process, and at its 

 base by the scaphoid fossa. The external plate is broad ; the space 

 between the two is the pterygoid fossa; it contains part of the internal 

 pterygoid muscle, and the tensor palati. Externally to the external 

 pterygoid plate is the zygomatic fossa. Behind the nasal fossse, in the 

 middle line, is the under surface of the body of the sphenoid, and 

 the basilar process of the occipital bone, and, still further back, the 

 foramen magnum. At the base of the external pterygoid plate, on 

 each side, is the foramen ovale, and behind this the foramen spinosum 

 with the prominent spine which gives attachment to the internal 

 lateral ligament of the lower jaw and the laxator tympani muscle. 

 Running outwards from the apex of the spinous process of the 

 sphenoid bone, is the fissura Glaseri, which crosses the glenoid 

 fossa transversely, and divides it into an anterior smooth surface, 

 bounded by the eminentia articularis, for the condyle of the lower jaw, 

 and a posterior rough surface for a part of the parotid gland. Behind 

 the foramen ovale and spinosum, is the irregular fissure between the 



