516 GANGLIA OF THE HEAD. 



From these ganglia an immense number of "branches 

 radiate in every direction, constituting so many plexuses. 

 The plexuses follow the course of the several arteries, re- 

 ceiving the names of the respective vessels they pursue, aa 

 the hepatic, gastric, splenic, renal, &c. In many in- 

 stances they form complete nervous sheaths around the 

 vessels. 



The sympathetic cords, it will be observed, in their de- 

 scent along the spinal column, connect with all the spinal 

 nerves by one or two filaments with the cervical gene- 

 rally by one, and with the dorsal, lumbar, and sacral by 

 two. At their superior extremity they also communicate 

 with all the cerebral nerves as they emerge from the cra- 

 nium, except the fourth and sixth pair, and with these they 

 unite in the cavernous sinus; while with the olfactory, 

 optic, and auditory, the union occurs in their ultimate ex- 

 pansion. There is also a communication of the sympathetic 

 nerves with the several ganglia of the head, which gan- 

 glia are regarded as the same with the rest of the gan- 

 glionic system. And though they have been described 

 along with the several organs of the head, yet for the pur- 

 pose of having a connected view of the whole we introduce 

 the following summary and figure (156.) 



Six sympathetic ganglia are found belonging to the 

 head, as follows : 



The ganglion of Eibes, named after its discoverer, and 

 situated upon the anterior communicating artery. This 

 ganglion is the point of junction of the sympathetic cords 

 of the opposite sides of the body, at their superior part. It 

 sends filaments to the carotid plexus. 



The lenticular , ciliary or ophthalmic ganglion, is situated 

 within the orbit, on the outside, and in close contact with 

 the optic nerve, and imbedded in a quantity of fatty mat- 

 ter. It is a small, flattened and grayish body, sending off 

 the ciliary nerves to the eye, and, according to Tiedemann, 

 a filament along with the arteria centralis retina. It 

 communicates^with the nasal branch of the ophthalmic, 

 with the third or motor oculi, and with the carotid plexus 



