5 6 ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



Fig. 61.— The left temporal bone divided through the axis of the petrous portion (f) 



Fig. 62.-The right temporal bone divided in a plane passing through the external auditory meatus and 



nearly parallel to the axis of the petrous portion (£). ' d 



Fig. 6 3 .-The right temporal bone divided in the upper half through the axis of the petrous portion 



and below horizontally, the wall of the canalis musculo-tubarius being partly chSed 



awav to show thp «pni„m f£\ & ^ l v Linbeiea 



away to show the septum (£). 



In this situation the spine of the sphenoid insinuates itself into the angle between the anterior 

 border of the pyramid and the cerebral surface of the squamosal portion, so that the .rroove 

 for the Eustachian tube (see page 51), running upon the inferior surface of the sphenoid & bone 

 leads into the orifice of the musculotubar canal. 



The external surface of the petrous portion forms part of the external surface of the base 

 of the skull. It presents quite a number of noteworthy structures and is the roughest and most 

 uneven surface of the bone. At its junction with the mastoid portion there is a rounded openin- 

 the stylomastoid foramen (Fig. 5 S), the external orifice of the facial canal, which traverses the 

 temporal bone in a curve and lodges principally the facial nerve. 



In front of the stylomastoid foramen is situated the styloid process (Fia S 55 and c8) the 

 remains of one of the branchial arches. Sometimes it is short and thick and sometimes 'it is 

 very long,* and it is usually placed in a sort of bony sheath, the vaginal process (Fi- cc) 

 which is mainly in contact with the process anteriorly and belongs to the tympanic portion! 

 I he styloid process gives origin to three muscles (stylohyoideus, styloglossus, and stylopharyn- 

 gcusj. 



^ To the inner side of the styloid process, toward the posterior border of the pyramid there 

 is a rounded or an oval depression, the jugular jossa (Fig. 58), which borders upon the jugular 

 notch. It lodges the upper extremity of the internal jugular vein (bulbus vena jugularis superior) 

 and at the bottom of it a small canal, the mastoid canaliculus (see page 58), begins as a groove.' 

 Near the jugular fossa, toward the apex of the pyramid and close to its posterior border is situ- 

 ated the small funnel-like orifice of the aquaductus {canaliculus) cochlea (Fig 58) 



Behind the jugular fossa and internal to the stylomastoid foramen, °the posterior border 

 of the pyramid presents a somewhat roughened surface for articulation with the occipital bone 



In front of the jugular fossa and separated from it by a narrow ridge, there is a large, almost 

 circular foramen, the external carotid foramen (Fig. 5 8), which leads into the carotid canal, the 

 posterior wall of which presents a number of small foramina, the external orifices of the carotico- 

 tympanic canahcuh, for the nerves of the same name. 



Between the external carotid foramen, the jugular fossa, and the external orifice of the 



acm;eductus cochlea, there is a small and sometimes poorly marked depression, the petrosal 

 fossa (Flg 58)j whlch contams the infcriQr aperturc Qf the ^^^^ ^.^ whkh ^^^ 



nuts the tympanic nerve. Internal and anterior to the external carotid foramen, and toward 

 the jommen lacerum there is a roughened surface for the origin of the levator veli palatini 



WSK CxT^ b0nC " freqUenUy qUitC *°* bUt " "^ ^ C ° ntinUed - a ""* *** in the ** 



