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17 Mammals generally.

As to details of the m. scutularis we note the following. In
the Dog (PL 15, fig. 5) — where the muscle is strongly developed
and extends far forward on the front — as well as in the Rabbit
and the Elk the hindmost dorsal part of the m. scutularis joins the
corresponding one of the other side across the head and forms a
great muscular plate going from one scutellum to the other. In
Swine an aponeurosis unites the dorsal ends of the scutularis-fibres
of the right and left side. In the Dog the foremost ventral part,
pars antero-ventralis nob. (PI. 12; PL 15, fig. 5), of the scutularis
has a certain similarity to the pars zygomatics platysmatis of
many Mammals and has indeed received the name: in. zygomatics
; it is a narrow oblique ribbon extending from the scutellum
into the upper lip; in the other forms with a scutellum
examined by us this part of the muscle is not developed in this
manner, and the whole ventral part does not extend far down
on the face. The scutularis of the Tapir (PL 7) is peculiar in
that a small anterior portion, taking its origin from the skull
above the e}^e, is connected through a rather long tendinous
band with the rest of the muscle, which otherwise does not extend
so far in front.

As mentioned above the pars transiens musculi scutularis is
composed of fibres of the scutularis crossing the scutellum and
of others arising from it. If we imagine, that the crossing
fibres of the pars transiens disappear, those of its fibres, which
take their origin from the surface of the scutellum would alone
be left, and the pars transiens would then appear as a separate
muscle arising from the scutellum. In Swine, at least in the
specimen figured (PL 9), this emancipation has for the most part
taken place, the dorsal bundles of the pars transiens being all
quite separate.

We make this remark because there arises from the scutellum
two muscles, which we think may possibly have been developed
from the scutularis in this manner and which therefore we rank
with the scutularis-complex. One of these is the m. levator brevis
(»kurzer Heber«) of the Veterinarians (PL 15, fig. 4), which arises
from the outer surface of the scutellum and is inserted into the
convex surface of the ear (Horse, Tapir, Elk, Cow; in the other
forms examined we have not found this muscle). As to the
derivation of this muscle from the scutularis comp. the description
of the scutularis of Didelphys given below. The other muscle,
which we are inclined to derive from the scutularis, is the m. rotator
(PL 15, fig. 5), a strong muscle arising from the inner surface
of the scutellum; its fibres are directed backward (and downward
) and inserted into the proximal part of the mediad side
of the auricle; in the Horse and Tapir it consists of two distinct
crossing portions1).

b. Auriculo-occipitalis-group.

PI. 15, fig. 4—6.

The m. auriculo-occipitalis is a lamelliform muscle taking its
origin on the occiput and the neck from a tendinous median
dorsal line, where it meets the corresponding muscle of the other
side; it extends over the pinna, into whose mediad side it is inserted
; in addition it is inserted into the scutellum, and the foremost
part of it frequently extends as a muscular plate on the
dorsal side of the head. It has its place behind the scutularis; as
far as it extends into the same region as this, it is covered by the
scutularis. The direction of the fibres of the auriculo-occipitalis is
posteriorly chiefly transverse, anteriorly longitudinal. The anterior
part, consisting of longitudinal fibres and extending on the dorsal
side of the cranium, we term the epicranial part; the next part, inserted
into the scutellum, we term the scutellular part, the last
part, inserted into the auricle, the auricular part. They may be
confluent or more or less separated. The epicranial part may
be wanting.

In the Dog (PL 15, fig. 5) the muscle is fully developed: it extends
on the auricle, is further inserted into the scutellum and
extends forwards on the dorsal side of the head (the lastnamed part

*) In the Cow, where the muscle has a more dorso-ventrad direction than usual,
a rather large foremost part of it inserts partially into the deeper portion of the m.
postauricularis, partially into a prominence of the skull above the bony meatus.

Ear-muscles in Placentals with a scutellum. 18

of the muscle is the m. epicranius s. occipitalis of Ellenberger-Baum,
Anatomie des Hundes). In a similar manner the muscle is developed
in the Rabbit, the Lama and the Elk: the muscle is inserted
into the auricle (in the Elk through a separate slip) and further
into the scutellum, and it is continued on the upper side of the
head. In the Swine examined the muscle is rather small; it is deeply
split up into five slips, of which the four first have all the same
direction: obliquely-forward; the hindmost of these four inserts
partially into the scutellum, the rest is epicranial. The fifth slip inserts
into the ear. In the Tapir (PL 7) the muscle is separated into
three portions, the hindmost inserting into the auricle; the two anterior
extend both beneath the scutularis, none of them reaching
the scutellum. In the Horse the epicranial part has disappeared, but
the auricular and scutellular are both well developed and only
partially separated; the scutellular part, which is a broad plate
largely tendinous, is generally described as a deep layer of the
m. scutularis. In the Cow the epicranial part has also disappeared
and the auricular and scutellular parts are intimately connected.

Inside the auriculo-occipitalis, from the same tendinous line
on the occiput and the neck, the musculus postauricularis (= m.
auricularis posterior of Ruge) takes its origin (PL 15, fig. 5). It consists
firstly (1) of a superficial part, which is inserted into a line
on the caudad side of the auricle; it is in the Swine a broad
fanshaped continuous muscular plate, but generally is split up
into two (Horse, Tapir, Cow, Rabbit) or three (Elk, Dog) digitiform
portions (PL 15, fig. 6), which at their origin generally cohere, but
more or less widely separated run to the auricle; of the three
digitations in the Dog the foremost is inserted into the scutellum,
but in the Elk all are inserted into the auricle (from the foremost
digitation in the Elk some fibres insert also into the scutellum
)1). Secondly (2) there is a deeper part, which arises posteriorly
either separately from the above-named tendinous line (Dog,
PL 15, fig. 5; Rabbit) or from the inner side of the superficial part
(Ungulata generally) or from both2) (Elk, PL 15, fig. 6); it inserts
below the insertion of the m. rotator hard above the incisura3)
2 + 3. — As to the original connection of the postauricularis
and the auriculo-occipitalis comp. the statements below on the
Marsupials.

To the auriculo-occipitalis-group further belong the muscles
which in the veterinary anatomical treatises are termed: mm. adductor
medius and inferior.

The m. adductor medius is, in the Swine (PL 9), quite a separate
muscle taking its origin from the inferior margin of the scutellum
and inserting into the anterior side of the auricle covered by the
pars transiens musculi scutularis. Also in the Tapir it is quite a
separate muscle. But generally in the animals examined it appears
partially as a continuation of the auriculo-occipitalis, some
of the fibres taking their origin from the scutellum but others
being a continuation of fibres of the auriculo-occipitalis. Such is
the case in the Rabbit, the Horse, the Cow and the Elk. In the Dog
(PL 15, fig. 5) the foremost slip of the m. postauricularis is inside
the scutellum confluent with the auriculo-occipitalis and from this
muscle part of the fibres of the adductor medius arise, while
others arise from the scutellum4).

While, from a comparison of the animals in question we
might contend that the adductor medius is a portion of the auriculo
-occipitalis, this is not possible with regard to the adductor
inferior, which is in all these forms quite a separate muscle; it
is only by taking the Marsupials into comparison that it may
be demonstrated, that this muscle also is part of the auriculo-
occipitalis (comp. below p. 21).

The m. adductor inferior (PL 15, fig. 4) is a fanshaped flat
muscle, which takes its origin from the lower margin of the scutellum
and from the face below it (sometimes from the zygoma)
and inserts round the incisura posterior 4 near the insertion of

x) The foremost of the two muscular slips in the Horse has a more caudad direction
than general and inserts into the auricle with a narrow tendon, not broadly as
usual; it gives rather the impression of a separate muscle (»mittlerer Heber«, levator
medius, of the Veterinarians).

2) Also in the Dog there is a connection between the superficial and the deep
part of the m. postauricularis (PI. 15, fig. 5).

3) Comp. as to »incisura«, »anteron« and »posteron«, Boas, Z. vergl. Anat. d.
Ohrknorpels der Saugetiere, in: Anat. Anzeiger 30. Bd., 1907, p. 434—42.

4) In the Dog there is a separate muscular slip, which inserts into the anteron 5 at
the inner angle of incisura 4, and which sometimes appears as a direct continuation
of the postauricularis; this little slip is not present in the other animals examined.

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