104 OSTEOLOGY. 



Superior constrictor muscle of the pharynx, with depressions on each side for the 

 insertion of the Rectus anticus major and minor. At the base of the external 

 pterygoid plate is the foramen ovale ; behind this, the foramen spinosum, and the 

 prominent spinons process of the sphenoid, which gives attachment to the internal 

 lateral ligament of the lower jaw and the Laxator tympani muscle. External to 

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

 fissure, the anterior portion being concave, smooth, bounded in front by the emi- 

 nentia articularis, and serving for the articulation of the condyle of the lower jaw; 

 the posterior portion rough, bounded behind by the vaginal process, and serving 

 for the reception of part of the parotid gland. Emerging from between the laminas 

 of the vaginal process 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. 

 l>y 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 a fibro-cartilaginous substance ; across its upper or cerebral aspect pass the 

 internal carotid artery and Yidian 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 tem- 

 poral bone, presenting from within outwards the quadrilateral rough surface, 

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

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

 aq uasductus 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 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 towards its cerebral aspect is divided into two parts 

 by a ridge of bone, which projects usually from the temporal, the anterior or smaller 

 portion transmitting the three divisions of the eighth pair of nerves; the posterior 

 transmitting the internal jugular vein and the ascending meningeal vessels, from 

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

 the carotid canal from the jugular fossa, is the small foramen for the transmission 

 of the tympanic 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 

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

 which serves for the attachment of the Rectus lateralis. On either side of each 

 condyle anteriorly is the anterior condyloid fossa, perforated by the anterior con- 

 dyloid foramen, for the passage of the hypoglossal nerve. Behind each condyle 

 are the posterior condyloid fossse, 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 the bone between them, 

 being rough for the attachment of numerous muscles. 



