Freiburger historische Bestände - digital

31

Elephant.

M. maxillo-labialis.

32

much greater space for traverses than is the case in the Elephant,
in which the muscle has become so narrow. That the maxillo-
labialis in the Elephant has been developed in a manner rather
different from that found in other Mammals is not surprising.
The portio inferior radiating like a fan in other Mammals (vide e.
g. the figures of Halmaturus, Horse, Dromedary, Tapir) has in the
Elephant become a long narrow muscle, whereas, on the other hand,
the portio superior has been developed into a powerful muscle,
which has widened its origin to the very median line and posteriorly
all over the fronto-nasal-region. It has been developed
into an enormously powerful raising muscle for the trunk, a
»m. levator proboscidis«, by which name all previous authors
have treated this muscle without, however, trying in the least to
explain its morphology. Such was also the case with the portio
inferior which only was put down as a »lateral, longitudinal
muscle« (vide e. g. Miall).

The longitudinal muscular system formed by the maxillo-
labialis on the dorsal and partly on the lateral circumference of
the trunk is, as is known, able to develop an enormous force,
just as it also has a considerable extent of motion, the trunk of
the Elephant possessing a wonderful mobility. The working powers
of a muscle are to a large extent determined partly by the
number of muscular fibres it contains, partly by the length of
the muscular belly; the former factor determines the force which
the muscle is able to develop, the latter, however, the extent of
its motion. In conformity to this the m. maxillo-labialis has in
the Elephant obtained an enormous length and a considerable
bulk of muscular fibres, which are to a large extent arranged in
a most singular manner, quite different from that of the muscle
in other Mammals.

The particulars in the structure of the muscle are as follows
(comp. PI. 1 and 2). It is very coarse-fibred and in its whole
course along the trunk is covered by a very strong fascia (PL 4,
where the fascia is dissected off on the proximal part of the
muscle), which, on the proximal part of the trunk is separated
from the corium by a layer of loose subcutaneus connective tissue
, so that the skin may here easily be taken off. But very
soon (about the end of the upper fourth of the trunk) the subcutaneous
connective tissue begins to be reduced and it soon
disappears, so that the corium throughout a very considerable
length of the organ (more than the half) is intimately united
with the fascia and cannot be separated from it. Posteriorly the
fascia proceeds on to the face, where it covers the proximal
part of the portio superior; here it gradually grows thinner
and is at last lost in the connective tissue on the frontal
surface.

In the proximal part of the portio superior, that is the part
thereof which extends across the nasal cartilage with its muscles,
from which the portio superior is separated by a layer of adipose
tissue, — the intramuscular connective tissue is very powerfully
developed, and forms thin fibrous longitudinal leaves,
which extend upwards through the muscular body between the
bundles and insert into the inner face of the fascia. Between
these leaves there are deep grooves or rather canals, being closed
above by the fascia, each of them quite filled up with coarse
fascicles.

In front of the cartilaginous nose where the portio superior
passes out upon the trunk these fibrous intramuscular leaves
proceed in the fibrous leaves that belong to the radiate muscular
system of the trunk (v. Plate 2 and PI. 14, fig. 2). As we shall
describe more fully below, there is in the trunk a considerable
system of muscular bundles that, from the wall of the nasal
canals, radiate upwards. They are arranged in long parallel rows
and each such row passes into a thin fibrous leaf that is inserted
into the inner face of the fascia. Between these rows of radiate
muscular bundles with their fibrous leaves, there are formed
long grooves or canals, in which the fascicles of both portions
of the maxillo-labialis are placed, similar to the grooves limited
by the leaves of the intramuscular connective tissue in the proximal
part of the portio superior; the grooves on the trunk are
deepest on its proximal part (some of the deepest grooves measured
1V2—2 cm in height and were 1—1V2 cm broad just below
the fascia), whereas they gradually grow lower and narrower
towards the distal end of the trunk.

These leaves present many special peculiarities (fig. D). Some
of them are of considerable length, and may be traced far down
the trunk with long intervening grooves; but no leaf reaches
continuously from the upper end of the^trunk to the lower one.
Other leaves are short (vide e. g. a and b in fig. D), some of the
shortest we found measured 2—3 cm. Now, if we follow such
leaves it is found that they suddenly stop with steep, truncated
ends (v. a in fig. D). At a shorter or longer distance distad of
this, one or two new leaves begin (v. b in fig. D) which may
then be traced for a shorter or longer extent. Hereby there arise
many singularities in the course of the grooves. If we follow a
groove (vide e. g. the grooves 7, 15, 17, 22, 23, 24 in the fig. D)
then, after a shorter or longer course we suddenly meet a leaf
that arises from the trough of the groove and at the sharp edge
of which the groove, as it were, splits into two. Sometimes this
is repeated several times in the course of a groove (v. e. g. the
grooves 7, 15, 17 in the fig. D) so that it is divided into several
parallel grooves. Sometimes we see how a groove splitting into
two by a leaf that juts out from its bottom, reunites at the
distal end of this leaf (v, e. g. the groove 7; the upper b). Besides
these peculiarities, determined by the length of the leaves,
and by their origin, there are others which arise by the formation
of abundant »anastomoses« between the leaves. The leaves
unite or amalgamate; and in details this is done in several ways.
Very frequently two leaves are found approaching each other,
uniting for a short space then parting again (vide e. g. the grooves

I, 2, 6, 8, 10, 13, 16, 17, 23). The groove is in this way interrupted
and at the »anastomoses* the two leaves are firmly connected
by short, tight fascicles of connective tissue. Sometimes
this is repeated several times in the course of a leaf so that it
»anastomoses« now with its mediad now with its laterad neighbouring
leaf (v. e. g. the plate between the grooves 1 and 2). In
other places there will be found two (v. e. g. the grooves 5, 11,

14, 15, 17, 24) or three leaves (v. the grooves 21—22) amalgamating
so that the intervening groove or grooves are closed.
Most frequently this form of »anastomoses« appears at the short
leaves, most of which join the long neighbouring leaves, but it
is also found now and then between the latter (v. e. g. the grooves

II, 24). The leaf formed by the anastomose then proceeds in
order to divide after a shorter or longer course (v. the grooves

15, 21) and to anastomose again etc. Upon the whole, there will
very frequently be found divisions of leaves, often in such a
manner that from the lateral faces of a leaf others arise which
generally stop after a shorter or longer course parallel to the leaf
of origin (v. e. g. the grooves 7, 15, 17); it looks as if a secondary
, proximally closed groove had, as it were, been cut off from
the main-groove, reuniting the latter at the distal end of the secondary
leaf.

On the dorsal face of the trunk and on the neighbouring
parts of its lateral circumference there is formed in this way a
system of longitudinal fibrous, or muscular-fibrous leaves radiating
through the wall of the trunk. Between them they include
grooves, in the course of which, however, many peculiarities
occur, brought about by the relations of the leaves mentioned
above. In these grooves the muscular portion of the maxillo-labialis
is imbedded, and so it becomes evident that an extremely
large surface of origin and insertion is afforded the muscle
by this arrangement, the leaves serving as surfaces for attachment
.

By the whole system of the radiate leaves the muscular body
is, as it were, divided into parallel, longitudinal sections each
consisting of a greater or smaller number of coarse bundles,
which may most easily be dissected and followed along their
whole length. The length of such sections differs considerably.
We found them up to 12—15 cm long. The proximal sections arise
from the aponeurosis on the nasal surface and project into the
grooves, where they show the following insertions: Some fascicles
end in short tendons, from the distal ends of which new fascicles