THE FIFTH, TRIGEMINAL OR TRIFACIAL NERVE. 641 
dental nerve). The anterior dental nerve supphes the incisor and canine teeth 
the middle dental nerve supples the premolar teeth. 
After emerging on the face from the infra-orbital foramen, the infra-orbital nerve 
divides into a number of radiating branches arranged in three sets—() palpebral, in 
the lower eyelid ; (}) nasal, for the skin of the side of the nose ; and (¢) labial, for the 
cheek and upper lip. ‘These branches form communications with the infra- ae 
branches of the facial nerve, known as the infva-orbital plexus (Fig. 458, p. 637). 
The spheno-palatine or Meckel’s ganglion (g. spheno-palatinum) occupies the 
upper part of the spheno-maxillary fossa. It is a small reddish-gray ganglion, 
suspended from the superior maxillary nerve by the two spheno- “ele ane iranehes 
which constitute its sensory roots. The motor and sympathetic roots of the ganglion 
are derived from the vidian nerve. This nerve is formed in the cavity of the skull 
upon the cartilage filling up the foramen lacerum medium, by the union of the 
great superficial “petrosal nerve from the geniculate ganglion of the facial nerve 
(emerging from the temporal bone through the hiatus Fallopiz) with the great deep 
petrosal nerve, a branch of the carotid plexus of the sympathetic on the internal 
carotid artery. The vidian nerve passes through the vidian canal to the spheno- 
maxillary fossa, where it ends in Meckel’s ganglion. 
The branches from the ganglion are seven in number. (a@) The pterygo-palatine 
or pharyngeal branch passes backwards through the pterygo-palatine canal to 
supply the mucous membrane of the roof of the pharynx. 
(>) The posterior palatine nerves, three in number, are directed downwards to the 
palate through the posterior palatine canals. The large posterior palatine nerve emerges 
on the under surface of the palate through the large posterior palatine canal, and at 
once separates into numerous branches for the supply of the mucous membrane of the 
soft and the hard palate. Its anterior filaments communicate with branches of the 
naso-palatine nerve. The main nerve gives off, as it hes in the posterior palatine canal, 
a small inferior nasal nerve which enters the nasal cavity and supplies the mucous 
membrane of the lower part of the outer wall of the nose. The small posterior 
palatine nerve descends through the small posterior palatine canal, and, piercing 
the tuberosity of the palate bone, i is distributed to the mucous membrane of the 
soft palate, uvula, and tonsil. It possibly conveys motor fibres to the levator palati 
and azygos uvule muscles. The accessory posterior palatine nerves are one or 
more small twigs which pass through accessory posterior palatine canals, and 
supply branches to the mucous membrane of the tonsil, soft palate, and uv ula. 
(¢) The branches directed inwards from Meckel’s ganglion enter the nasal cavity 
through the spheno-palatine foramen. They are two in number—the naso- 
palatine and the superior nasal. The superior nasal nerve is a small nerve 
destined for the mucous membrane of the upper and back part of the outer wall of 
the nose. The naso-palatine nerve, after passing through the spheno-palatine 
foramen, crosses the roof of the nose, and extends obliquely downwards and 
forwards along the nasal septum, grooving the vomer in its course, to reach the 
incisor foramen near the front of the hard palate. The nerves pass through the 
subordinate mesial foramina (of Scarpa), the left nerve in front of the right. In 
the incisor foramen the two nerves communicate together. They then turn back- 
wards and supply the mucous membrane of the hard palate. They communicate 
posteriorly with terminal filaments of the large posterior palatine nerves. In its 
course through the nasal cavity the naso-palatine nerve furnishes collateral branches 
to the mucous membrane of the roof and septum of the nose (Fig. 453, p. 634). 
(d@) The orbital branches, one or more minute branches, pass upwards to the 
periosteum of the orbit from Meckel’s ganglion. 
. Inferior Maxillary Nerve (nu. mandibularis).—The inferior maxillary nerve 
is formed by the union of two roots: a large sensory root, from the Gasserian 
ganglion, and the small motor root of the “trigeminal nerve, which is wholly 
incorporated with this trunk. The two roots pass “together beneath the dura mater 
of the middle fossa of the base of the skull to the foramen ovale, through which 
they emerge into the pterygoid region. Outside the skull they combine to form a 
single trunk, which soon separates into anterior and posterior divisions. 
“At its emergence from the skull the nerve is deeply placed beneath the middle 
41 
