214 THE SKELETON. 



to the spinous process is the glenoid fossa, divided into two parts by the Glaserian 

 fissure (page 176), the anterior portion concave, smooth, bounded in front by the 

 eminentia articularis, and serving for the articulation of the condyle of the lower 

 jaw ; 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 stylo-mastoid foramen, for the exit of the facial nerve 

 and entrance of the stylo-mastoid artery. External to the stylo-mastoid foramen is 

 the auricular fissure, for the auricular branch of the pneumogastric, bounded behind 

 by the mastoid process. Upon the inner side of the mastoid 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 great 

 wing of the sphenoid, behind by the apex of the petrous portion 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 opening 

 is filled up in the recent state by fibrous tissue ; across its upper or cerebral 

 aspect pass the internal carotid artery and Vidian nerve. External to this aperture 

 the petro-sphenoidal 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 

 muscles ; external to this surface the orifices of the carotid canal and the aquse- 

 ductus cochleae, the former transmitting the internal carotid artery and the ascend- 

 ing branches of the superior cervical ganglion of the sympathetic, the latter serving 

 for the passage of a small artery and vein to the cochlea. Behind the carotid 

 canal is a large aperture, the jugular fossa, 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 

 mater. 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 glosso-pharyngeal, pneumogastric, 

 and spinal accessory nerves. On the ridge of bone dividing the carotid canal from 

 the jugular fossa is the small foramen for the transmission of Jacobson's nerve; 

 and on the outer wall of the jugular foramen, near the root of the styloid process, 

 is the small aperture for the transmission of 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 cheek 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 occipito-atloid 

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

 perforated by the anterior condyloid foramen, for the passage of the hypoglossal 

 nerve and a meningeal artery. Behind each condyle is the posterior condyloid 

 fossa, perforated on one or both sides by the posterior condyloid foramina, 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, 

 whilst on each side are seen the superior and inferior curved lines ; these, as well 

 as the surfaces of bone between them, are rough for the attachment of the muscles, 

 which are enumerated on page 168. 



The Lateral Region of the Skull. 



The Lateral Region of the Skull is of a somewhat triangular form, the base of 

 the triangle being formed by a line extending from the external angular process 

 of the frontal bone along the temporal ridge backward to the outer extremity of 



