1078 A MANUAL OF ANATOMY 



and the other passes through the fissure between petrous and 

 squamous parts of the temporal bone to supply the mucous mem- 

 brane of the mastoid cells. 



Great Superficial Petrosal Nerve. — This nerve is a branch of the geniculate 

 ganglion of the facial nerve in the aqueduct of Fallopius. It enters the 

 middle fossa of the base of the skull through the hiatus Fallopii, and passes 

 forwards and inwards in a groove on the superior surface of the petrous part 

 of the temporal bone. Having passed beneath the Gasserian ganglion, it 

 enters the upper part of the foramen lacerum medium, where it is placed 

 on the outer side of the internal carotid artery, and it joins the great deep 

 petrosal nerve from the carotid sympathetic plexus. In this manner the 

 Vidian nerve is formed, which enters the pterygoid or Vidian canal by its 

 opening on the g,nterior aspect of the foramen lacerum medium, and so 

 reaches Meckel's ganglion in the spheno-maxillary fossa. The great super- 

 ficial petrosal nerve is accompanied by the petrosal branch of the middle 

 meningeal artery. 



Small Superficial Petrosal Nerve. — This nerve represents the continuation, 

 through the tympanic plexus, of the tympanic branch (Jacobson's nerve) 

 of the glosso-pharyngeal nerve. It is reinforced by a small branch from the 

 geniculate ganglion of the facial nerve, which joins it as it traverses a small 

 canal in the petrous part of the temporal bone, beneath the canal for the 

 tensor tympani muscle. The nerve enters the middle fossa through the 

 accessory hiatus on the superior surface of the pars petrosa. It then passes 

 for a little forwards and inwards, and leaves the cranial cavity through the 

 canaliculus innominatus (when present), or through the fissure between the 

 pars petrosa and the great wing of the sphenoid, or, it may be, through the 

 foramen ovale, after which it terminates in the otic ganglion. 



External Superficial Petrosal Nerve. — This nerve, which is inconstant, 

 passes from the sympathetic plexus on the middle meningeal artery back- 

 wards and outwards on the superior surface of the petrous part of the tem- 

 poral bone, and it leaves the cranial cavity through a minute aperture situated 

 within the thin margin of the hiatus Fallopii. It terminates in the geniculate 

 ganglion of the facial nerve. 



Interior of the Cavernous Sinus. — ^The interior of this sinus is 

 broken up by a number of delicate trabeculse, which are arranged in 

 a reticular manner. The outer wall of the sinus contains the follow- 

 ing cranial nerves, in order from above downwards : the third, the 

 fourth, the ophthalmic division of the fifth, and the superior max- 

 illary division of the fifth. These nerves, as they pass forwards, 

 are separated from the blood-current by the endothelial lining of 

 the outer wall of the sinus. The cavity of the sinus is traversed 

 by (i) the cavernous part of the internal carotid artery, accom- 

 panied by the cavernous sympathetic plexus, and (2) the sixth 

 cranial nerve, which lies in close contact with the outer side of the 

 internal carotid artery. These structures are also separated from 

 the blood-current by the endothelial lining of the sinus. 



For the processes and other sinuses of the dura mater see Index. 



Cavernous Part of the Internal Carotid Artery. — ^This part of the 

 internal carotid artery lies within the cavernous sinus, which 

 occupies the cavernous groove on the lateral aspect of the body of 

 the sphenoid bone. It is separated from the blood-current by the 

 endothelial lining of the sinus. The course of the vessel is at first 

 upwards, between the lingula sphenoidalis and the posterior petrosal 



