THE EXTERIOR OF THE SKULL 181 



serves for the articulation of the condyle of the mandible; the posterior portion, 

 rough and bounded behind by the tympanic part of the temporal, is sometimes 

 occupied by a part of the parotid gland. Emerging from between the laminae 

 of the vagina] process of the tympanic part is the styloid process ; and at the base 

 of this process is the stylomastoid foramen, for the exit of the facial nerve, and 

 entrance of the stylomastoid artery. Lateral to the stylomastoid foramen, between 

 the tympanic part and the mastoid process, is the tympanomastoid fissure, for the 

 auricular branch of the vagus. Upon the medial side of the mastoid process is 

 the mastoid notch for the posterior belly of the Digastricus, and medial to the notch, 

 the occipital groove for the occipital artery. At the base of the medial pterygoid 

 plate is a large and somewhat triangular aperture, the foramen lacerum, bounded 

 in front by the great wing of the sphenoid, behind by the apex of the petrous 

 portion of the temporal bone, and medially by the body of the sphenoid and basilar 

 portion of the occipital bone; it presents in front the posterior orifice of the ptery- 

 goid canal; behind, the aperture of the carotid canal. The lower part of this opening- 

 is filled up in the fresh state by a fibrocartilaginous plate, across the upper or 

 cerebral surface of w T hich-the internal carotid artery passes. Lateral to this aperture 

 is a groove, the sulcus tubae auditivee, between the petrous part of the temporal and 

 the great wing of the sphenoid. This sulcus is directed laterahvard and backward 

 from the root of the medial pterygoid plate and lodges the cartilaginous part of the 

 auditory tube; it is continuous behind with the canal in the temporal bone which 

 forms the bony part of the same tube. At the bottom of this sulcus is a narrow 7 

 cleft, the petrosphenoidal fissure, which is occupied, in the fresh condition, by a 

 plate of cartilage. Behind this fissure is the under surface of the petrous portion 

 cf the temporal bone, presenting, near its apex, the quadrilateral rough surface, 

 part of which affords attachment to the Levator veli palatini; lateral to this surface 

 is the orifice of the carotid canal, and medial to it, the depression leading to the 

 aquaeductus cochleae, the former transmitting the internal carotid artery and the 

 c arotid plexus of the sympathetic, the latter serving for the passage of a vein from 

 the cochlea. Behind the carotid canal is the jugular foramen, a large aperture, 

 formed in front by the petrous portion of the temporal, and behind by the occipital ; 

 it is generally larger on the right than on the left side, and may be subdivided 

 into three compartments. The anterior compartment transmits the inferior 

 petrosal sinus; the intermediate, the glossopharyngeal, vagus, and accessory 

 nerves; the posterior, the transverse sinus and some meningeal branches from the 

 occipital and ascending pharyngeal arteries. On the ridge of bone dividing the 

 carotid canal from the jugular foramen is the inferior tympanic canaliculus for 

 1 he transmission of the tympanic branch of the glossopharyngeal nerve; and on the 

 'vail of the jugular foramen, near the root of the styloid process, is the mastoid 

 oanaliculus for the passage of the auricular branch of the vagus nerve. Extending 

 forward from the jugular foramen to the foramen lacerum is the petrooccipital fissure 

 occupied, in the fresh state, by a plate of cartilage. Behind the basilar portion 

 of the occipital bone is the foramen magnum, bounded laterally by the occipital 

 oondyles, the medial sides of which are rough for the attachment of the alar 

 :igaments. Lateral to each condyle is the jugular process which gives attachment 

 :o the Rectus capitis lateralis muscle and the lateral atlantooccipital ligament. 

 The foramen magnum transmits the medulla oblongata and its membranes, the 

 accessory nerves, the vertebral arteries, the anterior and posterior spinal arteries, 

 and the ligaments connecting the occipital bone with the axis. The mid-points 

 on the anterior and posterior margins of the foramen magnum are respectively 

 irmed the basion and the opisthion. In front of each condyle is the canal for the 

 passage of the hypoglossal nerve and a meningeal artery. Behind each condyle 

 the condyloid fossa, perforated on one or both sides by the condyloid canal, for 

 the transmission of a vein from the transverse sinus. Behind the foramen magnum 



