THE CAROTID AND CAVERNOUS PLEXUSES. 801 



The Carotid Plexus. 



The carotid plexus is situated on the outer side of the internal carotid. Fila- 

 ments from this plexus occasionally form a small gangliform swelling on the under 

 surface of the artery, which is called the carotid ganglion. The carotid plexus 

 communicates with the Gasserian ganglion, with the sixth nerve, and the spheno- 

 palatine ganglion, and distributes filaments to the wall of the carotid artery and 

 to the dura mater (Valentin), while in the carotid canal it communicates with 

 Jacobson's nerve, the tympanic branch of the glosso-pharyngeal. 



The communicating branches with the sixth nerve consist of one or two fila- 

 ments which join that nerve as it lies upon the outer side of the internal carotid. 

 Other filaments are also connected with the Gasserian ganglion. The communi- 

 cation with the spheno-palatine ganglion is effected by a branch, the large deep 

 petrosal, which is given off from the plexus on the outer side of the artery, and 

 which passes through the cartilage filling up the foramen lacerum medium, and 

 joins the great superficial petrosal to form the Vidian nerve. The Vidian nerve 

 then proceeds along the pterygoid or Vidian canal to the spheno-palatine ganglion. 

 The communication with Jacobson's nerve is effected by two branches, one of 

 which is called the small deep petrosal nerve, and the other the carotico-tympanic ; 

 the latter may consist of two or three delicate filaments. 



The Cavernous Plexus. 



The cavernous plexus is situated below and internal to that part of the internal 

 carotid which is placed by the side of the sella Turcica in the cavernous sinus, 

 and is formed chiefly by the internal division of the ascending branch from the 

 superior cervical ganglion. It communicates with the third, the fourth, the 

 ophthalmic division of the fifth, and the sixth nerves, and with the ophthalmic 

 ganglion, and distributes filaments to the wall of the internal carotid. The 

 branch of communication with the third nerve joins it at its point of division ; 

 the branch to the fourth nerve joins it as it lies on the outer wall of the cavernous 

 sinus ; other filaments are connected with the under surface of the trunk of the 

 ophthalmic nerve; and a second filament of communication joins the sixth nerve. 



The filament of connection with the ophthalmic ganglion arises from the 

 anterior part of the cavernous plexus ; it accompanies the nasal nerve or con- 

 tinues forward as a separate branch. 



The terminal filaments from the carotid and cavernous plexuses are prolonged 

 along the internal carotid, forming plexuses which entwine round the cerebral and 

 ophthalmic arteries ; along the former vessels they may be traced on to the pia 

 mater ; along the latter, into the orbit, where they accompany each of the sub- 

 divisions of the vessel, a separate plexus passing, with the arteria centralis retinae, 

 into the interior of the eyeball. The filaments prolonged on to the anterior com- 

 municating artery form a small ganglion, the ganglion of Ribes, 1 which serves, as 

 mentioned above, to connect the sympathetic nerves of the right and left sides. 



The inferior or descending branch of the superior cervical ganglion communi- 

 cates with the middle cervical ganglion. 



The external branches are numerous, and communicate with the cranial nerves 

 and with the four upper spinal nerves. Sometimes the branch to the fourth 

 spinal nerve may come from the cord connecting the upper and middle cervical 

 ganglia. The branches of communication with the cranial nerves consist of 

 delicate filaments, which pass from the superior cervical ganglion to the ganglion 

 of the trunk of the pneumogastric and to the hypoglossal nerve. A separate 

 filament from the cervical ganglion subdivides and joins the petrosal ganglion of 

 the glosso-pharyngeal and the ganglion of the root of the pneumogastric in the 

 jugu,lar foramen. 



The internal branches are three in number the pharyngeal, laryngeal, and 

 superior cardiac nerve. The pharyngeal branches pass inward to the side of the 



1 The existence of this ganglion is doubted by some observers. 

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