CAVERNOUS PLEXUS. 665 



The cephalic portion of the sympathetic consists of four ganglia. 1. The 

 ophthalmic ganglion. 2. The spheno-palatine, or Meckel's ganglion. 3. The 

 otic, or Arnold's ganglion. 4. The submaxillary ganglion. These have been 

 already described in connection with the three divisions of the fifth nerve. 



The cervical portion of the sympathetic consists of three ganglia on each side, 

 which are distinguished according to their position, as the superior, middle, 

 and inferior cervical. 



CEEVICAL PORTION OF THE SYMPATHETIC. 



The Superior Cervical Ganglion, the largest of the three, is placed opposite 

 the second and third cervical vertebra, and sometimes as low as the fourth or 

 fifth. It is of a reddish-gray color, and usually fusiform in shape : sometimes 

 broad, and occasionally constricted at intervals, so as to give rise to the opinion, 

 that it consists of the coalescence of several smaller ganglia. It is in relation, 

 in front, with the sheath of the internal carotid artery, and internal jugular vein ; 

 behind, it lies on the Eectus Capitis Anticus Major muscle. 



Its branches may be divided into superior, inferior, external, internal, and 

 anterior. 



The superior branch appears to be a direct continuation of the ganglion. It 

 is soft in texture, and of a reddish color. It ascends by the side of the internal 

 carotid artery, and, entering the carotid canal in the temporal bone, divides into 

 two branches, which lie, one on the outer, and the other on the inner side, of 

 that vessel. 



The outer branch, the larger of the two, distributes filaments to the internal 

 carotid artery, and forms the carotid plexus. 



The inner branch also distributes filaments to the internal carotid, and con- 

 tinuing onwards, forms the cavernous plexus. 



CAROTID PLEXUS. 



The Carotid Plexus is situated on the outer side of the internal carotid. 

 Filaments 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 Casserian ganglion, with the sixth nerve, 

 and spheno-palatine ganglion, and distributes filaments to the wall of the carotid 

 artery, and to the dura mater (Valentin). 



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 Casserian ganglion. The communi- 

 cation with the spheno-palatine ganglion is effected by the carotid portion of 

 the Vidian nerve, which passes forwards, through the cartilaginous substance 

 filling the foramen lacerum medium, along the pterygoid or Vidian canal, to 

 the spheno-palatine ganglion. In this canal it joins the petrosal branch of the 

 Vidian. 



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 cavern- 

 ous sinus, and is formed chiefly by the internal division of the ascending branch 

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

 fifth, and sixth nerves, and with the ophthalmic ganglion, and distributes fila- 

 ments 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 



