Io2 THE SKELETON. 



attachment to the internal lateral ligament of the lower jaw, and the Laxatoi 

 Tympani muscle. External to the spinous process is the glenoid fossa, divided 

 into two parts by the Glaserian fissure (p. 144), the anterior portion concave, 

 smooth, bounded in front by the eminentia articularis, and serving for the articu- 

 lation 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 laminae 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. Ex- 

 ternal to the sty lot 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 plato is a large and somewhat triangular aper- 

 ture, 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 aper- 

 ture 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 passes 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 outwards, 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 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 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 in- 

 ternal 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 tym- 

 panic 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, bound- 

 ed 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 Eectus Lateralis. On either side of 

 each condyle anteriorly is the anterior condyloid fossa, perforated by the an- 

 terior condyloid foramen, for the passage of the hypoglossal nerve. Behind 

 each condyle are the posterior condyloid fossae, perforated on one or both sides 

 by the posterior cosdyloid 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 the muscles, which are enu- 

 merated on page 134. 



