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NERVUS FACIALIS OF THE ELEPHANT.

Plate 47.

The investigation of the ramification of the nervus facialis has
been made on No. 2 (supplemented by an investigation of Elephant
No. 1, as far as the nerves of the ear-muscles are concerned).

The nervus facialis projects from the skull through the foramen
stylomastoideum, proceeds in naso-lateral direction, covered
by the gl. parotis, and at the nasal border of this gland it appears
on the face, a little ventrally to the joint of the jaw. The nerve
trunk, which is here 1 cm broad and flattened, proceeds, covered
by the fascia parotideo-masseterica, for a short space on to the m.
masseter, parallel with and a few cm ventrally to the arcus zygoma-
ticus, and then divides into two final branches, ramus mandibulars
and ramus maxillaris.

While continuing under cover of the gl. parotis, the nervus
facialis sends out the following branches: n. auricularis posterior
(1) issues directly after the nerve having left the skull, and proceeds
in dorsal direction. A little further on, another branch
issues (la), joining the m. temporo-auricularis, and a few branches
(1 b), joining the m. postauricularis (deep portion). The nerve
proceeds, a little sinuous, in dorsal direction, along with and a
little anterior to the nasal border of the ear cartilage, covered by
the m. scutularis; at about the middle of the border of the cartilage
it divides into two branches, a nasal and a caudal one, which are
closely connected and continue their course, anastomosing on the
way, and ending in m. auriculo-occipitalis (1 d). From the caudal
branch ramifications issue to the m. postauricularis (lc; deep portion
), the m. transversus (1 e), the m. auriculo-occipitalis (1 d) and
the m. temporo-auricularis (1 a). — The n. auricularis internus (2),
much smaller than the preceding one, extends in dorsal direction
to the external ear. — The ramus digastricus (3) consists of 2 nerves
issuing at a short distance from each other. — The ramus
colli (4), a narrow branch extending to the platysma. — Finally,
from the dorsal border of the trunk of the nervus facialis, a little
posterior to the joint of the jaw, the ramus temporalis issues (5;
the n. auriculo-palpebralis of the veterinary anatomy), a rather
considerable branch, extending in dorsal direction, anterior to the
ear, and dividing into 2 branches, a caudal one (5 a), innervating
the m. scutularis and ending in the m. orbicularis oculi in the
dorsal eyelid. The nasal branch (5 b) extends rostrad under the
facial gland and ends in the m. postorbicularis and m. scutularis.
Both branches form plexuses while extending, the nasal one in
connection with a branch of trigeminus; a small branch enters
the gland.

The ramus mandibularis (6) is by far the thinner of the two
final branches, even if it must be designated as a nerve of some
importance. It extends in nasal direction, forming a ventrally
convex curve, ending in the lower lip. In its caudal part it is
covered by the platysma, forming under this cover a large plexus
together with branches from the ramus maxillaris and from a
branch of trigeminus; branches from the plexus ramificate towards
platysma and m. buccinatorius. In its nasal superficial part the
nerve sends out a branch to the platysma (6 a), several branches to
the m. buccinatorius (6 b) and one branch to the m. mentalis (6 c).

The ramus maxillaris (7) is of so considerable dimensions
that it appears as a direct continuation of the trunk of nervus
facialis. It proceeds further on the face, keeping the direction of
the trunk, passes the m. masseter where it is for the greater part
completely superficial, whilst anterior to this muscle it extends
through the large lump of fat filling out the deep, broad space
between m. buccinatorius and maxillare, whereafter the nerve extends
into the upper lip and further on into the proboscis. At
about off the middle of the m. masseter from the dorsal border
of ramus maxillaris a considerable branch issues (7 a) which extends
in dorsal direction and forms a plexus, from which branches
issue to the m. postorbicularis, m. orbicularis oculi in the ventral
eyelid, m. prasorbicularis and m. naso-labialis. From the ventral
border of the ramus maxillaris issue — besides the branches to the
plexus — several small branches to the m. buccinatorius (7 b) and
its pars rimana (7 c). The ramus maxillaris then extends into the
upper lip beneath the m. naso-labialis and m. nasalis and continues
further on to the extremity of the trunk; it is here extending
in curves, what is rare in nerves (found also in nerves in other
freely movable organs, such as the tongue). In the trunk the
ramus maxillaris fuses with branches from the 2. branch of trigeminus
, surrounded in common with these nerves by a thick
fibrous sheath, beneath the pars rimana and the pars supralabi-
alis of the m. buccinatorius and the m. maxillolabialis (PI. 14 fig. 2)
and innervates all the muscles of the upper lip and the trunk; on
its way it forms a few anastomoses with branches of trigeminus.
Already in the upper lip an especially long and thick branch
issues and extends on the medial side of and parallel with the
ramus maxillaris far out in the trunk without, however, reaching
the very tip. At the point where the ramus maxillaris enters the
upper lip a branch (7d) issues from its dorsal border, extends
in dorsal direction, divides into two branches and innervates the
m. maxillolabialis.

Ruge has, as we know, established a schedule of the ramification
of the n. facialis of the face, o: the part anterior to the
external ear, founded on investigations of the Prosimise. According
to this schedule the n. facialis ramificates into 3 main branches
: the ramus temporalis innervating the m. orbicularis oculi
in the dorsal eyelid and the m. orbito-auricularis; the ramus mandibularis
innervating the platysma, sphincter colli, m. buccinatorius
, m. orbicularis oris in the lower lip and m. mentalis; the
ramus maxillaris innervating m. orbicularis oculi in the ventral
eyelid, the muscles of the nose and upper lip, m. buccinatorius
and m. maxillolabialis.

As is easily seen from the above, an investigation of the n.
facialis of the Elephant leads to the result that the corresponding
ramification of n. facialis exactly agrees with this schedule, except
for the modification that the ramus maxillaris is so considerably
developed that it apparently appears as a direct continuation of
the trunk of the n. facialis.