2. The _internal mandibular_ branch arises at about the same level as the external mandibular, but under it, passes inward around the edge of the hyoid cartilage, under the adductor mandibularis muscle, and then forward along the mandibular cartilage.
3. The _hyoid_ branch separates from the hyomandibular trunk at about the same level as the preceding nerves, and then passes, deep in the tissues, around the angle of the jaw to the ventral side where it is distributed to the superficial constrictor muscles. Several nerves pass from the hyomandibular trunk and the hyoid branch to the dorsal superficial constrictors.
4. The _palatine_ branch springs from the base of the hyomandibular trunk inside the hyomandibular canal. It passes outward and forward, dividing into numerous branches which innervate the mucous membranes of the mouth. It can be traced completely later.
One or more small nerves proceeding to the pseudobranch and anterior wall of the spiracle arise near the point of origin of the palatine branch.
The _otic nerve_, passing from the root of the facial nerve to the postorbital canal, is not likely to be found in this dissection.
Observe the enlargement near the base of the hyomandibular trunk, and within the cartilaginous canal, the _geniculate ganglion_. The _gasserian ganglion_, a component of the trigeminal nerve, lies in the ventral portion of the trigeminal-facial root, and can now be located.
The _auditory nerve_ arises close behind the ventral division of the trigemino-facial root. The root of the auditory nerve encloses a large _auditory ganglion_. A _vestibular nerve_ arises from the anterior end of the auditory ganglion and passes into the ear capsule, innervating the upper part of the utriculo-sacculus and the ampullae of the anterior and horizontal canals. From the posterior part of the ganglion nerves pass to the ventral part of the sacculus and the ampulla of the posterior canal. Trace these branches as thoroughly as possible.
The _abducens nerve_ emerges from the cranium under and close to the origin of the posterior rectus muscle, into which muscle it enters. To expose this nerve the trigeminal, facial and auditory nerves must be lifted and cut as they pass through the wall of the cranium. It can be traced obliquely backward and inward, through a long canal, to its origin near the midline of the ventral surface of the medulla.