THE CILIARY GANGLION 961 



way of the tj'mpanic nerve, which is from the petrosal gangUon, with the tympanic plexus (fig. 



741). 



The tympanic plexus serves as a common point of distribution of fibres from the superior 

 cervical sjanpathetic ganghon, the ganglia of the vagus, the petrosal ganglion, and the geniculate 

 ganglion, to the cavernous and carotid plexuses and to the spheno-palatine and otic gangUa. 

 The superior cervical ganglion is associated with the cavernous and carotid plexuses direct by 

 the internal carotid nerve and with the tympanic plexus by the inferior and superior carotico- 

 tympanic nerves. The tympanic plexus receives fibres from the geniculate ganghon by a smaU 

 geniculo-tympanic branch and it is connected with the spheno-palatine gangUon by a small 

 anastomotic or tympano-petrosal branch to the great superficial petrosal nerve, and with the otic 

 ganghon by the small superficial petrosal nerve. It is not directly connected with either the 

 cihary or the submaxillary ganglion. However, these gangha, as well as the sphenopalatine 

 and otic, are connected with the carotid plexus either directly by named branches or indirectly 

 by way of plexuses derived from the carotid. The geniculo-tympanic branch, the tympanic 

 nerve and twigs of the nodosal plexus may be considered as analogous to the rami communicantes 

 of^the spinal nerves. 



The parotid branches, described above as branches of the auriculo-temporal nerve (from the 

 trigeminus) and as containing fibres from the glossopharyngeal, should be mentioned here as 

 belonging to the ganghated cephahc plexus. These branches are sympathetic fibres arising 

 in the otic ganglion and passing as branches of the ganghon to the auriculo-temporal in which 

 they remain till this nerve enters the parotid gland and then they are distributed to the gland. 

 The visceral motor or preganglionic fibres which terminate about their cells of origin in the otic 

 ganglion are derived from the glosso-pharyngeal nerve and pass successively through the tym- 

 panic nerve, the tympanic plexus, and the small superficial petrosal nerve to the otic ganglion. 



The tympanic nerve (tympanic branch of the glosso-pharjTigeal, or nerve of Jacobson), the 

 branch to the Eustachian tube {ramus tuboe), and the superior and inferior carotico-tympanic 

 branches are also described as branches of the glosso-pharyngeal nerve. These must hkewise 

 be considered as belonging to the gangliated cephahc plexus. 



For purposes of dissection, it may be more expedient to consider separately, 

 with its roots and branches, each of the larger gangha of the gangliated cephalic 

 plexus. Under this heading belong in part the geniculate ganglion of the glosso- 

 palatine nerve, and the ganglia of the glosso-pharyngeal and vagus, especially the 

 petrosal ganglion of the former and the jugular ganglion of the latter, from the 

 fact that these ganglia contain numerous cell-bodies of sympathetic neurones as 

 well as those of the sensory neurones of their nerves. 



These gangUa, however, have been described with their corresponding cranial nerves. The 

 sensory and motor roots of their sympathetic portions are contained in the roots of their nerves. 

 The geniculate probably has no sympathetic root. The sympathetic roots of the petrosal and 

 jugular ganglia are contained in the branches of the jugular nerve. The chief branches of 

 distribution of the geniculate are the geniculo-tympanic branch, the great superficial petrosal 

 nerve, and the external superficial petrosal nerve. The branches of the petrosal ganghon are 

 the tympanic nerve and its branches of the tympanic plexus. The chief branch of distribution 

 from the jugular ganghon is contained in the auricular branch of the vagus, or nerve of Arnold, 

 supplemented by sympathetic fibres in the trunk of the vagus itself. 



The principal cephalic sympathetic ganglia are the ciliary, the spheno-palatine 

 (Meckel's), the otic and the submaxillary. 



The Ciliary Ganglion 



The ciliary, lenticular, or ophthalmic ganglion lies in the posterior part of the 

 orbital cavity, about 6 mm. in front of the superior orbital (sphenoidal) fissure, 

 to the lateral side of the optic nerve, and between the optic nerve and the external 

 rectus muscle. It is a small, reddish, quadrangular body, compressed laterally, 

 and it measures about two millimetres from before backward (fig. 734) . 



Roots. — (a) Its motor or short root enters its lower and posterior angle and is a visceral 

 motor branch derived from the branch of the inferior division of the oculomotor nerve which 

 siipphes the inferior obhque muscle. The fibres of the motor root probably all terminate in the 

 cihary ganglion in connection with motor sympathetic neurones. 



(6) The sensory or long root passes through the upper and back part of the ganglion. It 

 is a branch of the naso-cihary (nasal) nerve and is, therefore, composed of fibres from the 

 trigeminus passing through the ganglion. 



(c) The sympathetic root consists of fibres derived from the cavernous plexus of the 

 sympathetic; it passes to the ganglion with the long root. 



Branches. — From three to six short ciliary nerves emerge from the anterior border of the 

 ganghon; they divide as they pass forward and eventually form about twenty nerves which are 

 arranged in an upper and a lower group, and the latter group is joined by the long cihary 

 branches of the naso-ciliary (nasal) nerve, now sensory and sympathetic (fig. 734). When 

 they reach the eyeball, the cihary nerves pierce the sclerotic around the optic nerve, and pass 

 forward in grooves on the inner surface of the sclera. The sympathetic fibres contained are dis- 

 tributed as motor fibres to the cihary muscle, the sphincter of the iris, and to the vessels of these 

 and of the cornea. 



