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Elephant.

Buccinator-group.

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the mandibular portion described; where the latter forms the
transverse layer that is by a layer of connective tissue distinctly
separated from the underlying longitudinal fascicles, whereas in
the lower half of the buccinator the longitudinal fascicles of the
maxillary portion, quite closely, and without any limit whatever,
join those of the mandibular portion. Thus the buccinator, in
its upper half, consists of two distinctly separated layers: a superficial
transverse layer, and a deep longitudinal layer, — in its
lower one, however, only of a longitudinal layer (comp. PL 16,
fig. 16). As to the longitudinal fascicles in the maxillary portion
it must however be remarked that they together form a rather considerable
mass as under their course numerous new fascicles are
added, arising, partly from the maxillary bone, and partly from the
external surface of the mucous membrane. The latter forms a
large and somewhat oblique fold (PI. 3) which juts far out being
on both surfaces used partly as insertion partly as origin of numbers
of the deep longitudinal fascicles of the buccinator.

The deep »longitudinal layer« of the buccinator, — that is,
the longitudinal fascicles belonging to the maxillary portion —
proceeds onwards as well in the upper as in the under lip forming
, immediately under the skin, a brim of fascicles that run
longitudinally through the lips: pars rimana (in PI. 4 this brim is
seen in the upper lip; in the under lip it is only visible posteriorly
as the upper lip projects so far to the side that it covers the
upper part of the under lip).

If we first examine the under lip, we see, in PI. 4, the lower
part of the deep longitudinal fascicles projecting in rather a considerable
number partly under, partly between, the fascicles of
the transverse layer, after which they bend obliquely downwards
in the under lip ending here with short pointed tendons, inserted
to the skin. The fascicles, however, reach only a short way —
a few centimeters — into the under lip; but at the same time
new fascicles have been added arising below the angle of the
mouth (PI. 16, fig. 16). The new fascicles run onwards in the under
lip, at first mixed up among the fascicles of the buccinator,
and where the latter end the new ones continue their course forwards
as an immediate continuation thereof. The new fascicles
extend, for a shorter or longer distance, forwards into the lip,
but as they end, other fascicles are added, which continue the
course farther on. In this way there is formed a continuous
brim — 1 or iy2 cm high, — of longitudinal fascicles which
may be followed forwards to about the base of the free spout-like
termination of the under lip where the fascicles end, at the same
time spreading somewhat.

The upper fascicles of the deep longitudinal layer of the
buccinator proceed above the angle of the mouth into the upper
lip (PI. 4), where, after a short course, they end with short
pointed tendons and in a way similar to that which obtains in
the under lip: new fascicles are added forming an immediate
continuation of the fascicles of the buccinator. In this way there
is formed a continuous border of longitudinal fascicles, but in
the upper lip they are present in far greater numbers than in
the under lip, so that the border becomes much broader; it, however
, is not very thick. The fascicles reach down to the free
margin of the upper lip, running in a bow corresponding to the
form of the lip; they proceed outside the fold around the incisor
reaching in front thereof out upon the trunk, where they continue
their course down to its very point, forming a superficial
muscular layer on its ventral, and partly its lateral face (PI. 1,
comp. PI. 16, fig. 16).

Before we follow the further course of the buccinator upon
the trunk we will compare the part already described with the
buccinator in the other Mammals examined, as is mentioned
in the General Part. We find then in the Elephant the two
layers generally found, a superficial transverse layer and a longitudinal
layer, which posteriorly at the origin pass so closely
into each other that they only form one layer. We have found
the same in several Ungulates (Tapir, Horse, Boar, Wapiti, Elk,
Zebu), and in several figures (PL 8, fig. 1 and the schemes PL 16,
fig. 1—15) the details of the relations of the fascicles to each
other are given. A comparison shows then that the state of

things in the Elephant recalls most nearly that found in the Pig
(PL 16, fig. 15); ventral longitudinal fascicles gradually taking the
transverse direction. In the Elephant, however, the transverse
layer is rather considerably reduced; it only occupies about the
upper half of the buccinator, whereas in return the longitudinal
layer, which owing to the reduction of the transverse layer lies
superficially on about the lower half of the buccinator, is by far
the more important and powerful. Indeed, it is probable that the
reduction is in a close connection with the peculiar form of the
cheek in the Elephant. For the cheek is short and — what must
be particularly emphasized — high, and has rather a considerable
mass (mucous membrane, glands, muscles, connective tissue)
so that the fascicles of the transverse layer run in a great arc
over the glands and the longitudinal fascicles; so the buccinator
will certainly most easily be able to perform its chief function —
that is, to hold the food in between the grinding surfaces of the
molars during the mastication — b}' means of longitudinal fascicles
. We shall in this respect also refer to the buccinator of
the Dog (v. the General Part p. 27 and comp. PL 16, fig. 17) in
which animal the cheek, as is known, also is very short; here the
transverse layer is reduced too since only the pars rimana remains
, whereas all the rest, the fascicles extending from upper
to lower jaw, is wanting. — By the reduction of the transverse
layer in the Elephant its share in the formation of the pars rimana
has also suffered; indeed the layer proceeds a short distance
into the upper lip but its fascicles have the same direction as in
the cheek and does not bend round the angle of the mouth as
is the case in other Mammals. So the pars rimana in the Elephant
is exclusively formed b}^ the longitudinal layer of the buccinator
. That it is really the pars rimana which is found in the
lips we think may be concluded from the fact that the longitudinal
layer of the buccinator in several other Mammals may also
contribute to the formation of the pars rimana (Wapiti, Zebu,
Swine, Erinaceus, Rabbit).

As we have said, the pars rimana proceeds down upon the
trunk throughout its whole length. The origin of the fascicles
proceeds, in front of the incisor, from the skin of the fold of the
upper lip round the tooth, upon the ventral face of the root of
the trunk. On the trunk the fascicles arise from a rather powerful
aponeurosis which covers its ventral face. On the proximal
part of the trunk it may be rather easily separated from the skin
as there is a thin layer of subcutaneous connective tissue; but
distad this layer is gradually reduced, so that the aponeurosis
is here closely united with the corium and onlv with difficult}^
may be dissected out. The line of origin of the fascicles is on
the upper half of the trunk only a short distance from the median
line, but under its further course it turns gradually more
and more laterad, reaching, on the distal part of the trunk, out
to the very lateral margin of the ventral face1); a broader and
broader piece of the ventral face of the trunk is therefore covered
by the aponeurosis (PL 14, fig. 9). From the whole of the margin
of the aponeurosis the fascicles arise and form a continuous superficial
layer in which the fascicles run obliquely distad and
dorsad, lying on the ventral and partly on the lateral circumference
of the trunk (PL 1). On the proximal part of the trunk,
where the fascicles are thick and coarse, they run rather steeply
dorsad so that they soon turn from the ventral on to the lateral
face (PL 4), but the farther one gets out upon the trunk the
more they take the direction obliquely forwards and on the most
distal part even so much that they almost become longitudinal.
The fascicles are inserted into the fascia, which covers the max-
illo-labialis; and upon the proximal end of the trunk, where the
fascia and the skin may easily be separated, this insertion into
the fascia is easily demonstrated (PL 4); but farther distad,
where the fascia and the corium melt together, the fascicles are

x) As long as the trunk is still covered with skin it has, — most distinctly on
its distal part — as is well known, an almost level ventral face, which, on each
side, by rather a projecting, notched, and fairly sharp edge is separated from the
smoothly arched dorso-lateral face; this outer relief is chiefly called forth by the
skin, whereas the muscles — and particularly the pars rimana — only slightly
contributes to this. When the skin is dissected off, the trunk assumes a more
cylindric or rather conical form.