CRANIAL GAIS 7 GLIA. 433 



SYMPATHETIC NERVES. 



The Sympathetic system consists of a series of ganglia, extending along 

 each side of the vertebral column from the head to the coccyx, communi- 

 cating with all the other nerves of the body, and distributing branches to 

 all the internal organs and viscera. 



It communicates with the other nerves immediately at their exit from 

 the cranium and vertebral canal. The fourth and sixth nerves, however, 

 form an exception to this rule ; for with these it unites in the cavernous 

 sinus ; and with the olfactory, optic, and auditory, at their ultimate ex- 

 pansions. 



The branches of distribution accompany the arteries which supply the 

 different organs, and form communications around them, which are called 

 plexuses, and take the name of the artery with which they are associated : 

 thus we have the mesenteric plexus, hepatic plexus, splenic plexus, &c. 

 All the internal organs of the head, neck, and trunk are supplied with 

 branches from the sympathetic, and some of them exclusively ; hence it is 

 considered a nerve of organic life. 



It is called the ganglionic nerve from the circumstance of being formed 

 by a number of ganglia; and from the constant disposition which it 

 evinces in its distribution, to communicate and form small knots or 

 ganglia. 



There are five sympathetic ganglia in the head ; viz. the ganglion of 

 Ribes ; the ciliary or lenticular ; the spheno-palatine, or Meckel's ; the 

 otic, or Arnold's; and the sub maxillary : three in the neck; superior, 

 middle, and inferior : twelve in the dorsal region ; four in the lumbar re- 

 gion ; and four or five in the sacral region. 



Each ganglion may be considered as a distinct centre giving off branches 

 in four different directions, viz., superior or ascending, to communicate 

 with the ganglion above ; inferior or descending, to communicate w r ith the 

 ganglion below ; external, to communicate with the spinal nerves ; and 

 internal, to communicate with the sympathetic filaments of the opposite 

 side, and to be distributed to the viscera. 



CRANIAL GANGLIA. 



Ganglion of Ribes, 

 Ciliary, or lenticular ganglion, 

 Spheno-palatine, or Meckel's ganglion, 

 Otic, or Arnold's ganglion, 

 Submaxillary ganglion. 



The GANGLION OF RIBES is a small ganglion skuated upon the anterior 

 communicating artery, and formed by the union of the sympathetic fila- 

 ments which accompany the ramifications of the two anterior cerebral 

 arteries. These filaments are derived from the carotid plexus at each 

 side ; and through their intervention, the ganglion of Ribes is brought into 

 connexion with the carotid plexus, and with the other ganglia of the sym- 

 pathetic. ^This ganglion, though of very small size, is interesting, as being 

 the superior point of union between the sympathetic chains of opposite 

 sides of the body. 



The CILIARY GANGLION (lenticular) is a small quadrangular and flattened 

 37 2c 



