THE SKULL AS A WHOLE 131 



meningeal artery, and the prominent spinous process of the sphenoid, which gives 

 attachment to the internal lateral ligament of the mandible and the Tensor palati 

 muscle. External to the spinous process is the glenoid fossa, divided into two parts 

 by the Glaserian fissure (page 88), the anterior portion concave, smooth, bounded 

 in front by the eminentia articularis, and serving for the articulation of the condyle 

 of the mandible; the posterior portion rough, bounded behind by the tympanic 

 plate, and serving for the reception of part of the parotid gland. Emerging from 

 between the laminae of the vaginal process of the tympanic plate 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. External to the stylo- 

 mastoid foramen is the auricular fissure, for the exit of the auricular branch of the 

 vagus, bounded behind by the mastoid process. Upon the inner side of the mas- 

 toid process is a deep groove, the digastric fossa; and a little more internally the 

 occipital groove, for the occipital artery. At the base of the internal pterygoid plate 

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

 in front by the greater wing of the sphenoid, behind by the apex of the petrous por- 

 tion of the temporal bone, and internally by the body of the sphenoid and basilar 

 process of the occipital bone; it presents in front the posterior orifice of the Vidian 

 canal ; behind, the aperture of the carotid canal. The basilar surface of this open- 

 ing is filled in the recent state by fibrocartilaginous substance; across its upper 

 or cerebral aspect passes the internal carotid artery. External to this aperture the 

 petrosphenoidal suture is observed, at the outer termination of which is seen the 

 orifice of the canal for the Eustachian tube and that for the Tensor tympani 

 muscle. Behind this suture is seen the under surface of the petrous portion of the 

 temporal bone, presenting, from within outward, the quadrilateral, rough surface, 

 part of which affords attachment to the Levator palati and Tensor tympani mus- 

 cles; posterior to this surface is the orifice of the carotid canal and the orifice of the 

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

 ascending branches of the superior cervical ganglion of the sympathetic, the latter 

 serving for the passage of a small artery to and a small vein from the cochlea. 

 Behind the carotid canal is a large aperture, the jugular foramen, 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 is divided into three compartments 

 by processes of dura. The anterior is for the passage of the inferior petrosal sinus; 

 the posterior, for the lateral sinus and some meningeal branches from the occipital 

 and ascending pharyngeal arteries; the central one, for the glossophary ngeal . 

 vagus, and spinal accessory nerves. On the ridge of the bone dividing the cdrotid 

 canal from the jugular foramen is the small foramen for the transmission of 

 Jacobson's nerve (tympanic branch of the glossopharyngeal) ; and on the wall 

 of the jugular foramen, near the root of the styloid process, is the small aperture 

 for the transmission of the auricular branch of the vagus nerve (Arnold's nerve). 

 Behind the basilar surface of the occipital bone is the foramen magnum, bounded 

 on each side by the condyles, rough internally for the attachment of the check or 

 odontoid ligaments, and presenting externally a rough surface, the jugular process, 

 which serves for the attachment of the Rectus capitis lateralis muscle and the lateral 

 occipitoatlantal ligament. The middle of the anterior margin of the foramen 

 magnum is called the basion. The mid-point of the posterior margin is called the 

 opisthion. On either side of each condyle anteriorly is the anterior condyloid fossa, 

 continued as the anterior condylar foramen, for the passage of the hypoglossal 

 nerve and often a meningeal branch of the ascending pharyngeal artery. Behind 

 each condyle is the posterior condyloid fossa, continued as the posterior condylar 

 foramen, for the transmission of a vein to the lateral sinus. Behind the foramen 

 magnum is the external occipital crest, terminating above at the external occipital 

 protuberance, while on each side are seen the superior and inferior curved lines; 



