518 



DISSECTION OF THE HEAD. 



Dissection 

 of carotid ; 



of sym- 

 pathetic 

 plexuses, 



cavernous 

 and carotid. 



Internal 



carotid 



artery 



winds 

 through 

 cavernous 

 sinus. 



Branches. 



Sympathetic 

 forms 



carotid 

 plexus, 



cavernous 

 plexus, 



union with 



cranial 



nerves. 



Distribu- 

 tion. 



Two super- 

 ficial petro- 

 sal nerves. 



the dura mater separately opposite the anterior condylar foramen ; 

 these unite at the outer part of that aperture. 



Dissection. The dissector should now turn to the examina- 

 tion of the trunk of the carotid artery as it winds through the 

 cavernous sinus. 



An attempt should be made to find two small plexuses of the 

 sympathetic on the carotid artery, though in a well-injected body 

 this dissection is scarcely possible. 



One of these (cavernous) is near the root of the anterior clinoiil 

 process ; and to bring it into view it will be necessary to cut off 

 that piece of bone, and to dissect out with care the third, fourth, 

 fifth, and sixth nerves, looking for filaments between them and 

 the plexus. Another plexus (carotid), joining the fifth and sixth 

 nerves, surrounds the artery as it enters the sinus. 



The INTERNAL CAROTID ARTERY appears in the cranium at the 

 apex of the petrous part of the temporal bone. In this part of its 

 course the vessel lies between the layers of the dura mater bound- 

 ing the cavernous sinus along the side of the body of the sphenoid 

 bone, and makes two bends so as to have the form of the letter S 

 reclined. It first ascends in the inner part of the foramen lacerum, 

 and then runs forward to the root of the anterior clinoid process ; 

 finally it turns upwards in the groove on the inner side of this pro- 

 cess, perforates the dura mater forming the roof of the sinus, and 

 divides into cerebral arteries at the base of the brain. In this 

 course the artery is enveloped by nerves derived from the sympa- 

 thetic in the neck. 



The branches of the artery here are some small twigs (arterise 

 receptaculi) for the supply of the dura mater and the bone, the 

 nerves and the pituitary body, and, opposite the anterior clinoid 

 process, the ophthalmic artery. 



The terminal branches of the carotid will be seen in the dis- 

 section of the base of the brain. 



SYMPATHETIC NERVE. Accompanying the carotid artery is a 

 prolongation of the sympathetic nerve of the neck, which forms 

 the following plexuses : 



The carotid plexus is situate on the outer side of the vessel, at 

 its entrance into the cavernous sinus, and communicates with the 

 sixth nerve and the Gasserian ganglion. 



The small cavernous plexus is placed below the bend of the artery 

 which is close to the anterior clinoid process, and is mainly 

 derived from that offset of the upper cervical ganglion which 

 courses along the inner side of the carotid artery. Filaments from 

 the plexus unite with the third, fourth, and ophthalmic nerves. One 

 filament is also furnished to the lenticular ganglion in the orbit, 

 either separately from, or in conjunction with the nasal nerve. 



After forming these plexuses, the nerves surround the trunk of 

 the carotid, and are continued on the cerebral and ophthalmic 

 branches of that vessel. 



PETROSAL NERVES. Beneath the Gasserian ganglion is the large 

 superficial petrosal nerve (fig. 240, 2 , p. 678) entering the hiatus 



