TEMPORAL BONE. 39 



the passage of filaments of the vestibular nerve. The inferior 

 depression terminates in two oval pits, which correspond with the 

 inferior part of the inner wall of the vestibule, and are also pierced 

 with openings for the passage of filaments of the vestibular nerve. 

 Upon the anterior wall of the inferior depression, and near to its 

 termination, is a spiral groove, perforated by minute openings for 

 the passage of the filaments of the cochlear nerve; and in the 

 centre of the spine is a foramen larger than the rest, which leads 

 into the central canal of the modiolus, tubulus centralis modioli. 

 This groove corresponds with the base of the cochlea, and is 

 termed the tractus spiralis foraminulentus. Upon the posterior wall 

 of the depression, and opposite to the spiral groove, is a longitudinal 

 groove leading to a foramen which transmits a considerable branch 

 of the vestibular nerve. Above the meatus auditorius internus is a 

 small oblique fissure, and a minute foramen ; the former lodges a 

 process of the dura mater, and the foramen gives passage to a 

 small vein. Further outwards, towards the mastoid portion of the 

 bone, is a small slit, almost hidden by a thin plate of bone ; this is 

 the aquceductus vestibuli, and transmits a small artery and vein of 

 the vestibule and a process of dura mater. Below the meatus, and 

 partly concealed by the margin of the posterior border of the bone, 

 is the aquocductus cochlece, through which passes a vein from the 

 cochlea to the internal jugular vein and a process of dura mater. 



The basilar surface is rough and irregular, and enters into the 

 formation of the under surface of the base of the skull. Projecting 

 downwards, near its middle, is a long sharp spine, the styloid pro- 

 cess, occasionally connected with the bone only by cartilage, and 

 lost during maceration, particularly in the young subject. At the 

 base of this process is a rough sheath-like ridge, into which the 

 styloid process appears implanted, the vaginal process. In front of 

 the vaginal process is a broad triangular depression, the glenoid 

 fossa, bounded in front by the eminentia articularis, behind by the 

 vaginal process, and externally by the rough lip of the processus 

 auditorius. 



This fossa is divided transversely by the glenoid fissure (fissura 

 Glaseri) which lodges the extremity of the processus gracilis of the 

 malleus, and transmits the laxator tympani muscle, chorda tympani 

 nerve, and anterior tympanic artery. The surface of the fossa in 

 front of this fissure is smooth, to articulate with the condyle of the 

 lower jaw ; and that behind the fissure is rough, for the reception 

 of a part of the parotid gland. At the extremity of the inner angle 

 of the glenoid fossa is the foramen for the Eustachian tube ; and 

 separated from it by a thin lamella of bone, called processus cochlea- 

 riformis, is a small canal for the transmission of the tensor tympani 

 muscle. Directly behind, and at the root of the styloid process, is 

 the stylo-mastoid foramen, the opening of exit to the facial nerve, 

 and of entrance to the stylo-mastoid artery. Nearer to the apex of 

 the bone is a large oval opening, the carotid foramen the com- 

 mencement of the carotid canal, which lodges the internal carotid 

 artery and the carotid plexus. And between the stylo-mastoid and 



