802 NERVOUS SYSTEM OF THE HORSE 
parotid gland, and passes between the origin of the superficial temporal and 
internal maxillary arteries medially and the superficial temporal vein laterally. It 
then crosses the posterior border of the ramus of the mandible ventral to the trans- 
verse facial artery and about an inch and a half (ca. 3.5-4 em.) below the articu- 
lation of the jaw. Emerging from beneath the parotid gland upon the masseter 
muscle, it receives the ventral branch of the superficial temporal nerve, and divides 
into dorsal and ventral buecal branches. The following collateral branches are 
given off, the first five being detached within the facial canal, and the others 
between the stylo-mastoid foramen and the border of the jaw. 
1. The great superficial petrosal nerve (N. petrosus superficialis major) arises 
from the geniculate ganglion.t| It passes through the petrosal canal, contributing 
a filament to the tympanic plexus, receives the deep petrosal nerve from the carotid 
plexus of the sympathetic, emerges through the foramen lacerum, and is continued 
as the nerve of the pterygoid canal to the sphenopalatine plexus and ganglia (Fig. 
647). 
2. A delicate branch (R. anastomoticus cum plexu tympanico) emerges from 
the geniculate ganglion and unites with a filament issuing from the tympanic plexus 
to form the small superficial petrosal nerve (N. petrosus superficialis minor); this 
ends in the otic ganglion. 
3. The stapedial nerve (N. stapedius) (Fig. 647) is a short filament detached 
from the facial nerve as it turns down in the facial canal. It innervates the stape- 
dius muscle. 
4. The chorda tympani (Tig. 647) is a small nerve which arises a little below the 
preceding and pursues a recurrent course in a small canal in the mastoid part of 
the temporal bone (Canaliculus chords tympani), to reach the tympanic cavity. 
It traverses the latter, passing between the handle of the malleus and the long branch 
of the ineus. Emerging through the petrotympanic fissure, the nerve passes down- 
ward and forward on the guttural pouch, crosses beneath the internal maxillary 
artery, and joins the lingual nerve. It sends twigs to the mandibular and sublingual 
glands, and through its incorporation with the lingual nerve furnishes fibers to the 
mucous membrane of the anterior two-thirds of the tongue which are believed to 
mediate the sense of taste. 
5. Anastomotic filaments unite with the auricular branch of the vagus near 
the stylomastoid foramen. 
6. The posterior auricular nerve (N. auricularis aboralis) arises from the 
facial at its emergence from the facial canal (Fig. 646). It runs upward and back- 
ward with the posterior auricular artery under cover of the parotid gland, and sup- 
plies the posterior and dorsal auricular muscles and the skin of the convex surface 
of the external ear. It anastomoses with branches of the first and second cervical 
nerves. 
7. The internal auricular nerve (N. auricularis internus) springs from the 
facial close to or in common with the preceding (Fig. 646). It ascends in the 
parotid gland just behind the styloid process of the conchal cartilage, passes 
through an opening in the cartilage, and ramifies in the skin of the concave surface 
of the ear. 
8. The digastric branch (R. digastricus) (Fig. 646) arises from the facial below 
the auricular nerves and descends under cover of the parotid gland. Its branches 
innervate the posterior belly of the digastricus, the stylo-hyoideus, and the occipito- 
hyoideus. At its origin it gives off a small branch which forms a loop around the 
great auricular artery or its posterior branch and rejoins the trunk. 
9. The auriculo-palpebral nerve (N. auriculopalpebralis) (Fig. 646) arises 
from the upper edge of the facial near the posterior border of the ramus. It ascends 
1 Although this nerve springs directly from the ganglion, it contains motor as well as sensory 
fibers. 
