828 THE NERVOUS SYSTEM 



many grey rami communicantes. Occasionally the number of rami is increased 

 to five or six. Th.^ ganglion is occasionally constricted at intervals — these constric- 

 tions affording an indication of the individual ganglia ))y the coalescence of which 

 the sujM'rior cervical ganglion is formed. 



Branches. — The branches of the superior cervical ganglion are the ascending 

 branch; branches which follow the distrit)Ution of the external carotid artery (nervi 

 molles); branches of communication to cranial nerves; pharyngeal nerves; the 

 superior cervical cardiac nerve, and branches to the upper cervical vertebrae and 

 their ligaments. 



1. The ascending branch enters the carotid canal in the temporal bone and 

 divides into a larger external l^ranch which forms the carotid plexus, and a smaller 

 internal branch which ends in the cavernous plexus. These plexuses connnunicate 

 frequently with one another around the artery, and may be regarded as different 

 parts of the same plexus rather than distinct plexuses. 



The carotid plexus is formed by repeatedly communicating branches, which 

 follow the internal carotid artery in the carotid canal, keeping close to the outer 

 side of that vessel. The following nerves arise from it: tympanic; great deep 

 petrosal; and a communicating branch to the sixth nerve. 



(a) The tympanic branch (small deep petrosal) enters a minute canal 

 (carotico-tympanic canal) in the temporal bone, by which it is conducted to the 

 tympanic plexus (page 768). 



(6) The great deep petrosal nerve passes forwards and inwards through the 

 cartilage which occupies the foramen lacerum medium, and unites with the great 

 superficial petrosal to form the Vidian ncrvo (]>age 755). 



(c) The branches to the Gasserian ganglion are given off from the plexus as 

 it emerges from the carotid canal. 



(d) The branches to the sixth nerve are very distinct, and can be easily seen 

 when the cavernous sinus is opened. They join the abducens as it is crossing the 

 outer side of the internal carotid artery. 



The cavernous plexus is placed on the inner side of the internal carotid artery 

 near the pituitary body. Its terminal offsets follow the ophthalmic and cerebral 

 liranches of the internal carotid artery. In addition to these it gives off the fol- 

 lowing branches : — 



(a) Communicating branches to the third, fourth, and ophthalmic divi- 

 sion of the fifth cranial nerves. 



(6) The sympathetic root of the lenticular ganglion. This root is usually 

 in the form of several fine filaments which enter the ganglion at its posterior 

 border. 



(c) Two or three fine twigs enter the pituitary body. 



2. The nervi molles are given off from the anterior part of the superior cervical 

 ganglion, and accompany the branches of the external carotid arter}-. yse have 

 already noted, in the description of the fifth cranial nerve, that the otic and sul>- 

 maxillary ganglia receive their sympathetic roots from plexuses of the sympathetic 

 Avhich reach them via the middle meningeal and facial arteries respectively. In 

 addition to these roots to the ganglia, vaso-motor branches, and twigs which enter 

 the parotid gland, are given off. Other twigs, taking a downward direction, enter 

 the intercarotic and thyroid bodies; the latter follow the course of the superior 

 thyroid vessels. 



3. Communicating branches to cranial nerves. — Branches of communication 

 arise directly from the gangliDU to join tlie vagus, glosso-pharyngeal, and hypo- 

 glossal nerves. Communications are effected Avitli the ganglia of the root and trunk 

 of the vagus, and with the jugular and petrous ganglia of the glosso-pharyngeal. 



4. The pharyngeal branches, four or five in number, pass downwards and 

 inwards l)ehind the external and internal carotid arteries to join the pharyngeal 

 plexus. 



5. The superior cervical cardiac nerve arises from the lower part of the 

 ganglion, or occasionally from the nerve-cord between the superior and middle 

 cervical ganglia. The nerves of the two sides run a corresponding course in the 

 neck, but differ in their arrangement in the thorax. In the neck, each nerve is 

 directed downwards on the prevertebral fascia in front of the longus colli muscle. 



