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19

Mammals generally.

Ear-muscles in Placentals with a scutellum. Do .in Marsupials. 20

the auricular portion of the sphincter profundus; the fibres have a
predominant longitudinal direction. Sometimes it arises almost
only from the scutellum (Elk), in others it arises only from the
face farther down (Dog, PI. 12; Cow); in the Horse it has been
divided into two quite separate muscles (»adductor inferior« and
»adductor externus« of the Veterinarians), of which only the upper
takes its origin from the scutellum. In the Swine (PI. 9) the
muscle is divided into three small portions, which together form
a three-lobed fan, and of which only the uppermost takes its
origin from the scutellum; the front ends of the others are connected
with the ends of the fibres of some of the scutularis-
bundles, of which a large part do not reach the scutellum in the
Swine. This is a secondary connection (comp. the Marsupials).

c. Musculus temporo-auricularis.

The m. temporo-auricularis1) (PI. 15, fig. 5) is a narrow, often
rather long muscle, which has its place along the cartilaginous
meatus and inserts into the anteron 5, below the rotator.
It takes its origin sometimes from the lower jaw (Dog, Rabbit),
sometimes from the bony meatus (Horse), sometimes from the
posterior end of the zygoma (Elk, Swine). The muscle is quite
independent and presents no connection with other muscles; it
might be thought probable that it is to be derived from one of
the two great muscular complexes described above, but there is
no indication of the way in which it may have arisen from any
of them.

d. Muscles which both arise from and insert into

the auricular cartilage.

The 772. anted sexti — = m. helicis major -f minor horn. —
(PI. 15, fig. 4; PI. 12) is a small muscle lying near the anterior
border of the ear before the anteron 6; sometimes it arises from
the anteron 5 and inserts into the anteron 7 (Dog, Swine); in
others it takes its origin from the posteron 4 or tragus (Horse, Elk).

Dog. Lies on the concave side of the auricle, near the anterior
border in the furrow before the anteron 6, taking its origin
from the proximal part of the anteron 5 and inserting into the
proximal margin of the anteron 7.

Rabbit. Lies along the very elongated anteron 6 on the corresponding
place as in the Dog. It is a long thin muscle.

Swine. Arises from the anteron 5 and inserts into the anteron
7, lying near the anterior margin — as in the Dog. But
in the Swine, where the muscle is rather strong, there is furthermore
a portion developed, intimately connected with the first
described, taking its origin from the margin of the incisura anterior
4.

Horse. Takes its origin from the posteron 4 (tragus) and lies
in the furrow outside the anteron 6, into which furrow it is
also inserted.

Elk. A rather broad muscle lying on the concave side of
the auricle proximad of the anteron 6 and taking its origin as
in the Horse from the posteron 4.

M. posteri septimi — = m. antitragicus horn. — (PI. 15, fig. 4;
PI. 9). Of the animals examined by us we have only found this
muscle in the Dog, Rabbit and Swine (PI. 9). In all these the
muscle inserts into the proximal margin of the posteron 7, which
in these animals is well developed; sometimes the insertion extends
somewhat on the external (Dog) or internal (Swine) face
of the posteron. As to the origin of the muscle, this is variable.
In the Swine it arises from the margin of the antitragus and
from the distal margin of the posteron 5. In the Dog it arises
from the proximal margin of the posteron 5 and from the convex
surface of the concha, but not from the antitragus. In the
Rabbit it arises only from the convex surface of the concha. (In
man it arises from the antitragus and goes to the posteron I)2).

M. fissuralis (PI. 15, fig. 4) takes its origin from the posteron 4

(tragus) and inserts into the anteron 5.

Dog. Takes its origin from the inflected margin of the tragus
and inserts into the concave surface of the anteron 5.

*) Of the Veterinarians falsely named m. tragicus and homologized with the muscle
of this name of man, which is quite another.

2) Qaain, Anatomy, Vol. 3, Part 3, 10. Ed. p. 75.

Rabbit. Covered by the m. trago-anterus and the adductor
inferior. It is a rather strong muscle, taking its origin from the
proximal part of the tragus and inserting into the proximal part
of the anteron 5. The proximal part of the muscle, which at the
insertion is confluent with the rest, is a long slender muscle
taking its origin from the bony meatus.

Horse. A short rather strong muscle going between the tragus
and the anteron 5, which overlaps the tragus.

Elk and Swine (PI. 9). Arises from the surface of the tragus
and inserts into the margin of the anteron 5.

We think this muscle is the true homologue of the m. tragicus
of man. This muscle has its place on the tragus and sometimes1
) it sends some bundles to the »spina helicis«, the homologue
of the anteron 5.

The m. trago-anterus we have only found in the Dog (PI. 9)
and Rabbit. In the Dog it arises with three slips: one takes its
origin from the outside, near the proximal border, of the tragus;
another from the outside of the posteron 3, the third from the
ear-cartilage between the posteron 2 and the anteron 2; all insert
into the anterior margin of the anteron 5. In the Rabbit it is a
very broad, short muscular band going from the very elongated
lateral margin of the tragus to that part of the anterior margin
of the ear which in the Rabbit represents the margin of the anteron
5.

In the Rabbit alone we have found a muscle, which covers
the fissure between the antitragus and the posteron 5, a layer of
transverse-oblique muscular fibres going from the antitragus to
the posteron 5. We propose for this muscle the name: m. anti-
trago-posterus.

Besides these muscles there may, on the convex surface of
the auricle, be present tracts of muscular fibres. They are called
m. transversi and obliqui and the direction of the generally short
fibres may be either longitudinal or transverse. In the Dog the
above-described m. posteri septimi is continued by such a muscular
tract across the auricle.

B. The ear-muscles of the
Marsupials.2)

The facts surveyed in the preceding part, with regard to the
ear-muscles of the Placentals, are better understood if the ear-
muscles of the Marsupials are also taken into consideration.

In Didelphys (PL 15, fig. 3; fig. A) there are two large lamelli-
form ear-muscles lying on the head above and in front of the
ear, from the eye to the neck; the two muscle-plates overlap one
another a little, the anterior being external. The anterior muscle,
the scuiularis, sends off a pars transiens, which segregating from
the rest of the muscle is inserted into the anteron 7; it entirely
resembles the muscular portion of the same name in the Placentals
. The rest of the muscle is continued into a rather narrow
but thick muscular body, lying directly above the ear-conch,
which gradually grows narrower and is inserted into the arched
surface of the ear-conch (PI. 15, fig. 3, scutularis, a). This part of
the muscle is intimately connate with the other great muscle-plate,
which it overlies. We think this narrow terminal part of the
scutularis corresponds to the levator brevis of the Horse and other
animals; like it, it is inserted into the auricle near the insertion
of the auriculo-occipitalis, which in Didelphys here overlies
it. This is not the case in the Horse and Elk, the auriculo-occipitalis
not extending so far on the auricle as in Didelphys.

The other large, lamelliform, muscle of Didelphys corresponds
to the auriculo-occipitalis + the postauricularis of the Placentals;
which two muscles are still continuous in Didelphys; moreover,
posteriorly, this great muscular plate is continued in such a manner
into the platysma behind the ear that it has quite the appearance
of a forward continuation of the last-named muscle, the
fibres of which here have the same direction as the neighbouring
fibres of the auriculo-occipitalis -f postauricularis; dorsally a natural
limit does not exist. The muscular plate may be divided
into three portions, which dorsally are continuous, but ventrally
are more or less separated through splits having a dorso-ventrad

x) Henle, Eingeweidelehre, 2. Aufl. p. 757.

2) In this group a scutellum is not developed.