THE FIFTH, TRIGEMINAL OR TRIFACIAL NERVE. 645 
of two roots which embrace the middle meningeal artery. The nerve passes back- 
wards beneath the external pterygoid muscle and between the internal lateral liga- 
ment and the neck of the lower jaw. Entering the substance of the parotid gland, 
it is directed upwards to the temple over the zygoma in company with the temporal 
artery. It is finally distributed as a cutaneous nerve of the temple and scalp, and 
reaches almost to the vertex of the skull. 
The auriculo-temporal nerve gives off the following branches:—(1) A small 
branch to the temporo-maxillary articulation. (2) Branches to the parotid gland. 
(3) A twig for the supply of the skin of the external auditory meatus (and mem- 
brana tympani). (4) Branches to the upper half of the pinna on its outer aspect. 
(5) Terminal branches to the skin of the temple and scalp. 
Tt has the following communications with other nerves :—(1) Important communica- 
tions are effected by the roots of the nerve, which are separately joined by small branches 
from the otic ganglion. (2) The parotid branches of the nerve are connected with branches 
of the facial nerve in the substance of the gland. (3) The temporal branch of the nerve 
is in communication superficially with the temporal branches of the facial nerve. 
The lingual nerve (n. lingualis) is the smaller of the two terminal branches 
of the posterior division of the inferior maxillary nerve. It proceeds downwards in 
front of the inferior dental nerve, beneath the external pterygoid muscle, to its lower 
border. After passing between the internal pterygoid muscle, and the ramus of the 
lower jaw, it crosses beneath the mucous membrane of the floor of the mouth in the 
interval between the mylohyoid and hyoglossus muscles and beneath the duct of 
the submaxillary gland. It sweeps forwards and inwards to the side of the 
tongue, to the mucous membrane over the anterior two-thirds of which it is 
distributed. 
Two nerves communicate with the lingual nerve in its course to the tongue -— 
(1) The chorda tympani branch of the facial nerve joins it beneath the external 
pterygoid muscle, and is incorporated with it in its distribution to the tongue. 
(2) The hypoglossal nerve forms larger or smaller loops of communication with 
the lingual nerve as they course forwards together over the hyoglossus muscle. 
Besides supplying the aforesaid branches to the mucous membrane over the 
sides and dorsum of the tongue in its anterior two-thirds, the lingual nerve supplies 
the mucous membrane of the outer wall and floor of the mouth. It also assists, 
along with the chorda tympani nerve, in forming the roots of the submaxillary 
ganglion. 
The submaxillary ganglion (ganglion submaxillare) is a minute reddish 
ganglion placed on the hyoglossus muscle, between the lingual nerve and the 
duct of the submaxillary gland. It is suspended from the former by two trunks, 
consisting for the most part of fibres of the lingual and chorda tympani nerves 
which at this point become separated from the lingual nerve and incorporated with 
the ganglion. The roots of the ganglion are—(1) an afferent root, derived from 
the lingual nerve ; (2) an efferent root, derived from the chorda tympani; and (3) a 
sympathetic root, from the sympathetic plexus upon the facial artery. 
The branches from the ganglion are distributed to the submaxillary gland and 
Wharton’s duct, and by fibres which become reunited with the trunk of the lingual 
nerve, to the sublingual gland. 
The inferior dental nerve (n. alveolaris inferior) is larger than the lingual 
nerve. It passes from beneath the lower border of the external pterygoid muscle 
to reach the interval between the ramus and internal lateral ligament of the lower 
jaw. Entering the inferior dental canal through the inferior dental foramen, it 
traverses the substance of the ramus and body of the lower jaw, distributing 
branches in its course to the teeth. A fine plexus is formed by the dental branches 
before they finally supply the teeth. 
Branches and Communications.—(1) The mylohyoid nerve is a small branch 
arising just before the inferior dental nerve passes through the inferior dental 
foramen. Grooving the ramus of the jaw in its course, it descends into the 
submaxillary triangle on the superficial aspect of the mylohyoid muscle. Concealed 
in this situation by the submaxillary gland and the facial artery, it is distributed 
41a 
b, 
