On the right side parts of the superficial muscles have been removed
and the scutiform cartilage turned back to display the
deeper muscles. _a_, Frontal part, _a′_, temporal part of
fronto-scutularis; _b_, interscutularis; _c_, cervico-scutularis;
_d_, _e_, scutulo-auricularis superficialis superior and medius;
_f_, zygomatico-auricularis; _g_, scutulo-auricularis superficialis
accessorius; _o_, cervico-auricularis superficialis; _q_,
scutulo-auricularis superficialis inferior; _t_, scutiform
cartilage; _u_, parieto-auricularis; _v_, cervico-auricularis
profundus major; _w_, cervico-auricularis prof. minor; _x_, _x′_,
scutulo-auricularis prof. major et minor; _y_, temporalis.
(Ellenberger-Baum, Anat. d. Haustiere.)
]
7. The =tragicus= or mastoido-auricularis is a small muscle which arises
from the temporal bone just behind the external auditory process and
from the annular cartilage; it passes upward to be inserted into the
lower part of the anterior border of the conchal cartilage.
The =intrinsic muscles= are very small and of little importance. They
are as follows:
1. The =antitragicus= consists of a few bundles which are attached to
the conchal cartilage behind the junction of its two borders, and are
partially blended with the insertion of the parotido-auricularis.
2. The =helicis= is a small muscle attached in a position opposite to
the preceding on the anterior border of the conchal cartilage; it
extends also into the depression between the two divisions of the
border. It is in part continuous with the insertion of the
parotido-auricularis.
3. The =verticalis auriculæ=[221] is a thin stratum of muscular and
tendinous fibers which extends upward on the posterior surface of the
concha from the eminentia conchæ.
=Actions.=—The base of the concha is rounded and rests in a pad of fat
(Corpus adiposum auriculæ), so that the movements of the external ear
resemble those of a ball-and-socket joint. It is noticeable that
movements about the longitudinal and transverse axes are accompanied by
rotation. When the ear is vertical or drawn forward (“pricked up”), the
opening is usually directed forward; conversely, when the ears are “laid
back,” the opening faces backward. These movements evidently result from
the coördinated actions of several muscles which are very complex and
cannot be discussed in detail here. The scutularis acting as a whole
fixes the scutiform cartilage, so that the muscles which arise on the
latter act efficiently on the concha. The anterior auricular muscles in
general erect the ear and turn the opening forward. The interscutularis
concurs in this action, causing adduction and a symmetrical position of
the ears; it also acts directly on the conchal cartilage, since the
scutulo-auricularis superficialis superior is in reality a conchal
insertion of the interscutularis. The scutulo-auricularis superficialis
accessorius draws the concha forward and turns the opening outward. The
parieto-auricularis adducts the concha and inclines it forward. The
cervico-auricularis superficialis is chiefly an adductor of the conchal
cartilage, and directs the opening outward. The cervico-auricularis
profundus major turns the opening outward and, acting with the
parotido-auricularis, inclines the ear toward the poll. The
cervico-auricularis profundus minor tends to direct the opening downward
and outward. The parotido-auricularis draws the ear downward and
backward, and acts with the cervico-auricularis profundus major in
“laying back the ears”; the deep auricular muscles concur in these
actions. The tragicus shortens the external auditory canal. The actions
of the intrinsic muscles are inappreciable.
The =arteries= of the external ear are derived from the anterior
auricular branch of the superficial temporal, the posterior or great
auricular branch of the internal maxillary, and the anterior branch of
the occipital artery.
The =motor nerves= to the muscles come from the auricular and
auriculo-palpebral branches of the facial nerve and from the first and
second cervical nerves. The sensory nerves are supplied by the
superficial temporal branch of the mandibular nerve and the auricular
branch of the vagus.