960 



THE NERVOUS SYSTEM 



and branches of a cranial nerve (oculomotor, masticator, etc.) to enter and terminate in contact 

 with the cell-bodies of the gangUon, which, in their turn, give fibres to the branches of the gang- 

 hon; (bj fibres of the same origin, name and course but which may pass through the ganglion to 

 terminate in contact with the cells of a more distant ganglion. Any root, the motor especially, 

 may contain somatic motor fibres, that is, fibres of central origin which pass thi-ough the gang- 

 lion uninterrupted and into its branches to terminate upon the fibres of skeletal (voluntary) 

 muscle. 



A sympathetic root hkewise may carry two and perhaps three vai'ieties of fibres conforming 

 to the name : (a) fibres arising from the cells of other sympathetic ganglia and terminating in the 

 ganglion in question; (b) fibres arising in other ganglia which pass through the ganglion in 

 question to enter its branches and terminate either in other ganglia or upon their allotted mus- 

 cular or glandular elements. A third is the fibre of the sensory sympathetic neurone, probably 

 quite rare, which may arise from a cell-body in the ganglion and pass centralward in its root and 

 in the appropriate cranial nerve to terminate about a cell-body of the dorsal-root or spinal gang- 

 hon type, the central process of which latter conveys this sensory impulse of sympathetic origin 

 into the central system just as sensory cranio-spinal impulses are conveyed. 



Fig. 745. — Diagram to Illustrate the Structural 

 Branches of a Cephalic Sympathetic Ganglion. 

 sympathetic, black. 



Sensory fibre terminating in capsule 

 of ganglion and capsule of its cells 



Sensory root 



Motor root 



Relations of the Roots and 

 Sensory fibres, blue; motor, red; 



Sympathetic root 



Branches of distribution 



The branches of distribution of the ganglia, the larger of them often called nerves, are those 

 bundles in which the fibres, both arising in or passing through the ganglia, course toward their 

 terminations upon their allotted tissue elements of the head. The larger ganglia of the head are 

 described as each possessing the three roots above mentioned. In the branches pass fibres 

 motor to the vessels of the head, to the intrinsic muscles of the eye bulb, to the [lacrimal glands, 

 the mucous membranes (gland cells) of the nasal and oral cavities and the salivary glands, and 

 sensory fibres conveying impulses from these structures. 



The plexuses into which the gangliated cephalic plexus is divided and which connect the 

 ganglia to form it, are ruunerous and vary greatly in size. They underlie the mucous membranes 

 and they surround all the vessels and glands. They are named according to their locality. 

 The largest of them are the tympanic plexus and the carotid and cavernous plexuses. They 

 have been repeatedly referred to in their relations to the branches of the cranial nerves. 



Of the numerous branches described from the superior cervical sympathetic ganglion, the 

 two large ones which pass upward associate it especially with the gangliated cephalic plexus. 

 That branch known as the internal carotid nerve may be considered as the direct continuation 

 upward of the ganghatcd sympathetic trunk of the body. Through the branches of this, the 

 carotico-tympanic and the deep petrosal nerves, and through tlie plexuses derived from it, the 

 superior cervical ganglion may be associated with practically all the other sympathetic ganglia 

 of the head (figs. 7'.i9 and 741). The other branch from the superior cervical ganglion, the 

 jugular nerve, associates it with the ganglia of the glosso-pharyngcal and vagus nerves, with the 

 petrosal ganglion by a direct branch and with the ganglia of the vagus through the nodosal 

 plexus. These latter ganglia (and the nerves to which tliey belong) are connected, chiefly by 



