Freiburger historische Bestände - digital

91

The skull.

The skull of the Indian Elephant.

92

On the inferior face of the nasal bone and of the adjoining
part of the intermaxillary bone there is a large hole, which is
often divided into two by a vertical rim on the border of the two
bones. This hole is the entrance to an air-sinus filling most of
the interior of the nasal bone, while in young Elephants it only
more superficially excavates the upper part of the intermaxillary.
If the hole and therewith the air-sinus is divided into two, one
of them belongs to the nasal bone, the other to the intermaxillary.
In older Elephants (g) the first extends from the nasal bone into
the anterior part of the frontal, in the quite old (Chang) it fills
even a large part of the dorsal wall of the brain-case; also that
belonging to the intermaxillary bone is considerably deepened in
older individuals.

In one case, the young Elephant b, there is in the right nasal
bone instead of the described air-sinus only a shallow groove,
and the air-sinus in the bone is derived from the air-sinuses of
the frontal bone, emitting a diverticulum into the nasal bone. In
the left nasal bone of the same individual the ordinary air-sinus
is present as usual and fills the whole bone.

In the limitation of the nasal cavity also partakes the palatine
bone (PI. 31 fig. 5, PI. 32 fig. 5), the ascending part of which,
being as usual applied to the inner side of the maxillary bone, is
a very thin and feebly developed plate, which — at least in some
elephantine skulls — is cleft in an anterior and a posterior part,
the canalis pterygopalatine being for its greater extend represented
by a mere fissure, only its inferior extremity being a veritable canal.

A bone which in many Mammals forms a larger or smaller
part of the limitation of the nasal cavity is the lacrymal bone.
In the Elephant that is not the case; the bone (PI. 25 fig. 1) is
here very feebly developed, in most specimens without any trace
of the lacrymal canal, and does not form any part of the wall
limiting the nasal cavity. As usual it is placed between the maxillary
and the frontal bones. At its posterior end it reaches in the
skull b the maxillary sinus and forms a minimal part of its wall;
at the anterior end, which is endowed with a blunt, rather high,
freely projecting protuberance, the right lacrymal bone in the
skull b is on the side, which is applied to the maxillary bone,
feebly hollowed out through a prolongation from the maxillary
sinus, while the left lacrymal bone of the same skull is deeply
hollowed out through a diverticulum from an air-sinus of the
frontal bone.

In the skull c the right lacrymal possesses exceptionally a well
developed lacrymal canal with an orbital opening on the lateral
(hind) side of the bone; the canal opens into the nasal cavity
near behind the opening of the maxillary sinus. In the left lacrymal
there is a trace of the canal, but it is obliterated, being to a
large extent filled with osseous tissue; into this bone extends a
diverticulum from an air-sinus in the frontal bone.

Like the nasals also the frontal bones have been extraordinarily
shortened; and the median parts of them have been pushed
backwards. This becomes more marked as the animal grows older
(PI. 22—23). In the fetal skull a (PI. 22 fig. 1) the anterior end
of the suture between the two frontals is situated a little behind
the middle of the orbita; the dorsal parts of the two frontals make
together a bended transverse ribbon, the anterior and posterior
margin of which are almost parallel; the ribbon is about five
times broader than long. In the skull b (fig. 2) the anterior end
of the suture lies already a little behind the postorbital process
of the frontal; in the skull d (fig. 3) the same point lies 3—4 cm
behind the postorbital process and in e c. 10 cm. With the age the
ribbon becomes more and more bent and its median part particularly
increased in length, the breadth of the two frontals being
for instance already in the young skull b only 3—4 times that of
the length in the median line. The concavity of the anterior frontal
margin grows deeper and deeper and correspondingly the nasal
bones lying in it are pushed backwards; while in our fetal skull
the anterior end of the nasal bones extends a little beyond the
anterior margin of the orbit, in the oldest Elephant it does not
reach the posterior margin of it.

As to the position of the orbita in the skull of the Elephant
we may in this place make the following remarks. In the skulls
b, bx, b2 the orbita is still situated above the grinders or the first
of these reaches even a little before the orbit. But already in the

skulls c (PI. 25 fig. 1) and d the anterior margin of the orbit is
in advance of the anterior end of the grinder series, and in the
older Elephants the orbit is wholly or almost wholly in front of
the teeth, decidedly so in „Chang" (PI. 25 fig. 2). Probably this
is an outcome of the mighty development of the temporal muscle.
Gomp. the Manatee (p. 83).

As to the peculiar conditions of the placing of the grinders
of the Elephant it should firstly be emphasized, that the part of
the skull in which these teeth are implanted has a very peculiar
place, being, contrary to the usual condition, pushed backwards
below the brain-case, the grinders entering into an intimate connexion
with the basisphenoid. The special circumstances are as
follows.

From the hard palate extends in the Mammals generally backwards
a pair of large vertical plates of very different length, one
on each side of the nasopharyngeal cavity: the lamina? pterygoidea?.
They are composed of the hindmost part of the palatine bone,
of the pterygoid process of the basisphenoid and of the os ptery-
goideum; laterally it is (on the border of the alisphenoid) in many
Mammals perforated by a horizontal canal, canalis alisphenoidalis
(through which passes the arteria maxillaris int., a branch of caro-
tis externa). Posteriorly the lamina is often cleft in two branches
embracing a large pit, in which the m. pterygoideus int. takes its
origin. Frequently the os pteryg., which forms part of the median
side of the pit, is early fusing with the proc. pteryg. of the basisphenoid
. That is also the case with the Elephant, in which the os
pteryg. is quite early united at the top with the proc. pteryg. (already
in the fetus examined), while farther down both in the fetal
skull and in the skull b it is separate.

On the lateral side of the lamina pterygoidea in many young
Mammals extends a posterior outgrowth of the maxillary bone,
containing the germs of the posterior molars: processus molaris
(PI. 30 fig. 1). It is, at least partially, through a broader or narrower
fissure, separated from the palatine bone. In the fig. 1 PI. 25
and in fig. 1 PL 32 this process is seen in a young Bear, the first
molar of which (m1) has cut, but in which the second molar still
lies in the said outgrowth. In the last figure is also seen that from
the feeble postorbital process a rounded rim goes downwards and
hindwards, finally passing into the external margin of the alisphenoid
canal; in old Bears (PI. 32 fig. 2) this rim: the orbital
crest, crista orbitalis, is more sharply marked, directly before it
a series of openings (foramina ethmoidalia, foramen opt., fissura
orbit.) are found.

Now in the Elephant the case is this, that the processus molaris
is applied to the lateral surface of the lamina pterygoidea
— which is here sagittally very shortened — and is covered by
the inferior part of the orbital crest, which in the Elephant is
very prominent; or perhaps it is preferable to say that the proc.
molaris is immersed into the enormously widened alisphenoid
canal, the margin of the anterior opening of which loosely covers
it as a large plate. The lamina pterygoidea in this manner forms
a deep thin-walled bowl round the processus molaris; the bony
wall of the proc. mol. being thus covered is partially very thin or
even membranous. The proc. molaris is still present in the oldest
Elephant at our disposal (Chang); while in most Mammals the
proc. mol. totally disappears, when the last molar has got into
use, for instance in the Bear (PI. 32 fig. 2), where it is so prominent
in the young. Yet in the Ox (PI. 30 fig. 2), Camel and
others it persists as a strong outgrowth, separated from the lamina
pterygoidea through a rather broad cleft.

The two processus molares are in the Elephant of so large
extent that they have, as it were, forced themselves into the body
of the basisphenoid, in which are hollowed out two cavities, a right
and a left, that nearly meet in the median line of the bone, being
only separated by a thin vertical dissepiment. In the skull b the
basiphenoid is so largely hollowed out that also ventrally the bone
is in several points reduced to a membrane of connective tissue
or to a quite thin bony plate of silkpaper thickness. In these
cavities the processus molares are lodged. They do not extend
into the basioccipitale, although they reach nearly the posterior
end of the basisphenoid and in the skull g (PL 28 fig. 1—2), in
which it has been dissected out, overlies the anterior end of the
petrosal bone. In our oldest Elephant (Chang), in which most