16 ANATOMY. 



Opening of the Canal of Hugier, lies in the angle between the squamous 

 and petrous portions of the bone; and transmits the chorda tympani nerve. 

 Temporal Ridge,/ in part. 



Describe the Mastoid Portion. It projects like a nipple from the inferior 

 portion of the bone posteriorly. Internally it is grooved for the lateral sinus ; 9 

 externally are seen the 



Mastoid Foramen,*- the largest of several foramina, for a vein. 



Mastoid Process, at the tip, for the sterno-cleido-mastoid, splenius, and 



trachelo-mastoid muscles. 



Digastric Fossa,j for the posterior belly of the digastric muscle. 

 Occipital Groove* for the occipital artery. 

 Mastoid Cells, in the interior of the mastoid process, open on the posterior 



wall of the middle ear, and are lined with mucous membrane. 

 Describe the Petrous Portion. It is very hard, pyramidal in form, con- 

 tains the internal and middle ear, projects inwards and forwards, and presents 

 a base, an apex, three surfaces, and three borders. 

 On the Base are seen, the 



jr IG . 2 . Meatus Auditorius Externus,i the 



external opening of the ear. 

 Auditory Process, a bony ring for the 

 external cartilage of the ear. 



Apex lies internally, at the base of the 

 skull, forming the outer boundary of 

 the foramen lacerum medium, and 

 contains the internal carotid canal. 



Anterior Surface, presents from within, 

 outwards 



Opening of the Carotid Canal, 11 for 

 the internal carotid artery and 

 plexus. 



Depression, for the Gasserian ganglion of the 5th pair of cranial nerves. 

 Hiatus Fallopii, for great petrosal nerve and an artery. 

 Foramen, for small petrosal nerve. 



Eminence, over the superior semicircular canal of the ear. 

 Depression, over the tympanum. 

 Posterior Surface, presents 

 Meatus Auditorius Internus^ transmits the yth and 8th pairs of cranial 



nerves and the auditory artery, and lodges a process of dura mater. 

 Opening of the Aqueduclus Vestibuli^ transmits to the vestibule a small 

 artery and vein, and lodges a process of dura mater. 



