148 A MANUAL OF ANATOMY 



of the Eustachian tube, and, when followed outwards and backwards, 

 it leads to the Eustachian canal in the angle between the squamous 

 and petrous portions of the temporal. 



On either side of the basilar process of the occipital is the foramen 

 lacerum medium. It lies between the basilar process, the apex of 

 the petrous portion of the temporal, and the great wing of the sphe- 

 noid near the root of the pterygoid process. In the recent state it 

 is closed below by fibrous tissue, which is pierced by a meningeal 

 branch of the ascending pharyngeal artery, and one or more emissary 

 veins from the cavernous sinus. 



In a line extending backwards and outwards from the foramen 

 lacerum medium are the following markings on the inferior surface 

 of the petrous portion of the temporal : the rough surface from 

 which the levator palati arises ; the carotid foramen, which 

 transmits the internal carotid artery and the ascending branch 

 of the superior cervical ganglion of the sympathetic ; a minute 

 foramen, on the posterior wall of the vertical portion of the carotid 

 canal, for the tympanic branch of the carotid sympathetic plexus 

 and tympanic branch of the internal carotid artery; the jugular 

 fossa, which forms part of the jugular foramen ; the tympanic 

 canaliculus, on the ridge between the carotid foramen and jugular 

 fossa, for the tympanic branch (Jacobson's nerve) of the glosso- 

 pharyngeal and the tympanic branch of the ascending pharyngeal 

 artery ; and the auricular canaliculus, on the outer wall of the 

 jugular fossa, for the auricular branch (Arnold's nerve) of the 

 pneumogastric. Between the petrous portion of the temporal 

 and the jugular process of the occipital is the foramen lacerum 

 posterius or jugular foramen, which lodges the commencement of 

 the internal jugular vein, and transmits the following structu es : 

 the glosso-pharyngeal, pneumogastric, and spinal accessory nerves ; 

 the inferior petrosal sinus ; and meningeal branches of the ascending 

 pliaryngeal and occipital arteries. 



External to the front of the occipital condyle is the anterior] 

 condylar foramen for the hypoglossal nerve and a meningeal branch 

 of the ascending pharyngeal artery. The under surface of the 

 basilar process of the occipital presents the pharyngeal tubercle 



The posterior division is limited in front by a transverse line 

 on a level with the anterior margin of the foramen magnum, 

 and behind by the external occipital protuberance ana thf 

 superior curved line at either side. It is formed by the supra j 

 occipital and condylar portions of the occipital, and the mastoicj 

 portions of the temporal bones. 



In the middle line is the foramen magnum, which transmits tlui 

 medulla oblongata and its membranes, the spinal accessory nerves 

 the vertebral arteries, the anterior and posterior spinal arteries, anc 

 parts of the cerebellar amygdalae. The centre of the anterio 

 margin of the foramen magnum is known as the basion, and th 

 centre of the posterior margin as the opisthion. Proceeding outward 



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