GANGLIATED CEPHALIC PLEXUS 959 



pierces the sterno-mastoid, supplies filaments to it, and interlaces in its substance with branches 

 of the second cervical nerve. It emerges from the posterior border of the sterno-mastoid 

 slightly above the level of the upper border of the thyreoid cartilage, passes obliquely downward 

 and backward across the occipital portion of the posterior triangle, and disappears beneath the 

 trapezius about the junction of the middle and lower thirds of the anterior border of that muscle 

 (fig. 743). In the posterior triangle it receives communications from the third and fourth 

 cervical nerves, and beneath the trapezius its fibres form a plexus with other branches of the 

 same nerves. Its terminal filaments are distributed to the trapezius and they can be traced 

 almost to the lower extremity of that muscle. 



Central connections. — The nuclei of origin, like other motor nuclei, are connected with the 

 somsesthetic area of the cerebral cortex of the opposite side by the pyramidal fibres, and they are 

 associated with the sensory nuclei of other cranial nerves by the medial longitudinal fasciculus, 

 and with sensations brought in by the spinal nerves by the fibres of the fasciculi proprii. 



THE GANGLIATED CEPHALIC PLEXUS 



The Sympathetic Ganglia of the Head and Their Associations with 



THE Cranial Nerves 



The sympathetic system of the head, like that of the remainder of the body 

 described below, is arranged in the form of a continuous ganghated plexus subdi- 

 vided into sub-plexuses. UnUke the great unpaired prevertebral plexuses in the 

 thoracic and abdominal cavities, all the larger sympathetic ganglia of the head are 

 paired, gangha corresponding to each other being found on either side. Thus 

 they maj^ be considered as an upward extension of the series of paired lumbar, 

 thoracic and cervical ganglia belonging to the sympathetic trunks lying along 

 either side of the vertebral column. Numerous small ganglia, many of them 

 microscopic, occur in the sub-plexuses throughout the head. These are irregular 

 in size and position and those in the region of the median line are no doubt 

 unpaired. 



In origin, the ganglia of the cephalic plexus consist of cell-bodies which, in the early stages 

 of development, migrated from the fundaments of the ganglia of the vagus, glosso-pharjTigeal 

 and glosso-palatine nerves, and most especially from that of the semilunar (Gasserian) ganglion 

 of the trigeminus — a developmental relation identical with that of the remainder of the sym- 

 pathetic system to the ganglia of the spinal nerves. Just as is known for the spinal ganglia, 

 some cell-bodies destined to develop into sympathetic neurones, instead of migrating, remained 

 within the confines of the ganglia of the above nerves, in company with the cell-bodies of their 

 sensory neurones. This is thought to be especially true for the geniculate, the petrosal and the 

 jugular ganglion. Therefore these ganglia must be considered as in small part sympathetic 

 ganglia. 



The gangliated cephalic plexus could properly be included as a division of the general sym- 

 pathetic system described later. However, because its larger ganglia are so intimately asso- 

 ciated with branches of the oculomotor, trigeminal, masticator, glosso-palatine, glosso-pharyngeal 

 and vagus nerves, it is customary to describe it in connexion with the cranial nerves. 



The larger ganglia, one on either side of the head, comprise the ciliary ganglion, 

 the spheno-palatine (Meckel's) ganghon, the otic and the submaxillary ganglion. 

 To these must be added portions of the geniculate, petrosal, jugular and the gan- 

 glion nodosum, and a part of the superior cervical sj-mpathetic ganglion. The 

 chief relations of the gangliated cephalic plexus to the cranial nerves are shown in 

 fig. 741. 



The so-called roots and branches of the ganglia carry three varieties of fibres: 

 (1) Sensory, (2) Motor (visceral motor or preganglionic), and (.3) Sympathetic. 

 Most roots and branches are mixed, the name of a root being determined only by 

 the variety of fibres predominating in it. 



A bundle of sensory fibres going to a ganghon is called its sensory root. Such, however, 

 cannot comprise a true root since none of its fibres arises in the ganghon and very few or none may 

 terminate in it. The only sensory fibres terminating in a ganghon are the few which may ap- 

 proach it in any of the roots to terminate in its capsule or the capsules of its cells and convey 

 impulses of general sensibility from the ganghon to the central nervous system. Almost all of 

 the fibres of a "sensory root" merely pass 9 round or through a ganghon and into its branches 

 beyond, which they borrow as paths for reaching their allotted fields of distribution. In this 

 relation it should be reahzed that while the cihary, spheno-palatine, otic and submaxillary 

 ganglia are customarily described under the discussion of the trigeminus, this nerve has func- 

 tionally less to do with them than any of the other cranial nerves with which they are associated. 

 Bundles of trigeminal (sensory) fibres, traceable in gross anatomy because meduUated and of 

 appreciable size, pass to the ganglia, but only to pass through them as continuations of the ter- 

 minal branches of the trigeminus. 



The so-called motor root of a ganglion ma}' carry two kinds of fibres: (a) visceral motor 

 (preganghonic) fibres, arising in the nuclei of origin in the central system and passing in the trunk 



