THE CEANIAL OR ENCEPHALIC NERVES. 733 



COLLATERAL BRANCHES OP THE PNEUMOGASTRIC NERVE. 1. FILAMENTS 

 OE THE INFERIOR CERVICAL GANGLION. Always very slender, these some- 

 times come from the pharyngeal ramuscule. 



2. PHARYNGEAL NERVE (Figs. 339, 6 ; 342, 15). Originating from the 

 pneumogastric nerve at the middle part of the superior cervical ganglion, 

 the pharyngeal passes forwards and downwards on the side of the guttural 

 pouch, and gains the upper face of the pharynx, where it terminates in 

 forming a plexus with the pharyngeal branch of the ninth pair. This is a 

 sensory-motor branch. It gives off a large division that passes backwards 

 to the surface of the middle and posterior constrictor muscles, to which it 

 gives branches, and, throwing off a filament to the external laryngeal nerve, 

 reaches the commencement of the oesophagus ; it descends on the outside 

 of that canal by becoming distributed in its muscular tunic. This division, 

 which we have named the msophageal branch of the pharyngeal nerve, may 

 be traced on the oesophagus to the lower part of the neck, and in some 

 subjects even into the thoracic cavity. 



3. SUPERIOR LARYNGEAL NERVE (Fig. 339, 7). More voluminous 

 than the preceding, and arising a little lower, this nerve follows an 

 analogous course to reach the side of the larynx, where it enters the 

 aperture below the appendix of the superior border of the thyroid cartilage, 

 to be almost entirely expended in the laryngeal mucous membrane, to 

 which it communicates a very exquisite degree of sensibility. 



At the inner face of the thyroid cartilage, it presents several branches 

 that are directed forward, upward, and backward. The first pass to the 

 mucous membrane at the base of the tongue and the two faces of the epi- 

 glottis. The second are distributed in the lateral walls of the pharynx. 

 Of the third, some are destined to the mucous membrane of the arytenoid 

 cartilages and that of the oesophagus ; while others descend on the thyro- 

 arytenoid and lateral crico-arytenoid muscles, to unite with the branches 

 coming from the recurrent, and form an anastomosis analogous to the 

 anastomosis of Galien (Fig. 341, 5). 



Before penetrating the larynx, and even very near its commencement, 

 it furnishes a motor filament to the crico-pharyngeal and crico-thyroid 

 muscles ; this filament either arises directly from the pneumogastric nerve, 

 or, as is most frequently the case, from the pharyngeal ramuscule ; this is 

 the external laryngeal nerve of anthropotomists (Fig. 339, 8). It receives 

 accessory branches from the superior cervical ganglion, the cesophageal 

 branch, and the pharyngeal nerve, and is then distributed to the muscular 

 tunic of the oesophagus. It is to the union of this branch with the cesopha- 

 geal branch of the pharyngeal nerve, that we have given the name of superior 

 O3sophageal nerves. 1 



4. COMMUNICATING FILAMENTS WITH THE INFERIOR CERVICAL GANGLION. 

 These do not always directly enter this ganglion, for when the middle 

 cervical ganglion exists they pass to it. They are not similarly disposed 

 on both sides. The filaments of the right pneumogastric, two or three in 

 number, are extremely short, though voluminous. The left pneumogastric 

 usually only furnishes a single, long, thin ramuscule, which is detached in 

 the region of the neck near the point where the pneumogastric commences 

 to separate from the cervical branch of the sympathetic, an4 reaches the 

 inferior cervical ganglion by remaining alongside the principal nerve. 



1 Toussaint has seen this branch leave the oesophagus to lie beside the recurrent ; 

 but its filaments always return to that canal a* ascending twigs. 



