Freiburger historische Bestände - digital

97

The skull.

The skull of the Indian Elephant.

98

and in d it is also apparently still wholly open1. But in / it has
been wholly obliterated and only faint traces of the suture can be
seen on the upper surface. The suture between the two frontals is
still very distinct in /.

The parietal is very early united with the supraoccipital. In
the fetal skull a the parietals are still separate from the supra-
occipital; but in b the suture on the upper side of the skull is
certainly in most places open, but the obliteration has non the
less begun and on the inner side of the skull the suture is already
rather effaced. In the somewhat older skulls c and d the suture
is also nearly wholly effaced on the upper side of the skull. The
right and the left parietal are separate in the fetal skull and also in
the skull b; but in the older skulls they are united.

A conspicuous interparietal is not developed in the Elephant;
but in the skull b1 there is in the place of the interparietal an
unpaired little bone, 3 cm long and 1—2 broad, lying between
the hind ends of the parietals and posteriorly bordering on the
supraoccipital; this little bone is very distinct on the inside of
the skull, the suture being here open, while on the upper side
it is to a great extent obliterated. In the skulls a and b this same
bone is represented by a pair of minor bones lying between the
parietals and the supraoccipital; in b they are partially united with
the parietals. In older Elephants there are at most faint traces
of the interparietal, which is wholly united with the adjoining
bones.

Quite different from the relations between the parietals and
the supraoccipital are those of the exoccipital and the squamosal
to the adjoining bones. In the skull / the supraoccipital is wholly
separated from the two exoccipitals, which meet above the foramen
magnum, and the supraoccipital and the exoccipital are likewise
separated from the squamosal; and in e the exoccipitals are also
still separated from the basioccipital (in / the sutures between this
bone and the exoccipitals are only partially open). In g the suture
between the exoccipital and the squamosal and partially also that
between the exoccipital and the supraoccipital are still open. The
squamosal is still in d quite separate from the parietal. But in e
the suture between squamosal and parietal is closed on some
limited points above, while otherwise it is open, and in / we still
find the same. Great parts of the suture are still open in g and h.
The suture between the squamosal and the alisphenoid is still open
in the skull g.

The tympanicum and petrosum, which in the fetus a are still
separate, are already united in b (but rests of the suture between
them are still exstant), while both are separate from squamosum.
This is also the case with all the other skulls examined, with the
only exception of Chang, in which all the bones of the skull are
united.

The suture between the basioccipital and the basisphenoid is
still quite open in e, but already wholly obliterated in /.

The jugal is still quite separate in an Elephant as old as k.
But in Chang it is coalesced with the maxillary and the squamosal.

The measure, in which the sutures are obliterated in the Elephantine
skull, is obviously correlated with the special development
of the skull. If the transverse sutures between the frontal,
the parietal and the supraoccipital are so early obliterated, this
is evidently the consequence of the slight longitudinal growth of
the skull. This is also the reason why the suture between the
basioccipital and the basisphenoid is rather early obliterated. —
If on the other hand the exoccipital, lying beneath the supraoccipital
, is rather late fusing with this, it is obviously connected with
the vertical growth of the skull being more extensive than the
horizontal. That the petroso-tympanicum for a very long time
keeps separate from the adjoining bones, presumably is the consequence
of the considerable growth in transversal direction of
that region. — If the maxillary is only very late united with the
frontal, from which it is separated through a horizontal suture
(a suture parallel with the grinding surface of the molars), we
have no doubt that this is in connection with the mighty vertical
growth.

It is strange that the squamosal in some places rather early
coalesces with the parietal, while extended parts of the suture
remain open for a long time. One should think that even
a quite limited coalescence would be a hindrance to the bones

from receding from each other and thus be an equally large hindrance
to the considerable vertical and transverse growth, which
takes place in this region, as a more extended occlusion of the
suture. But perhaps the few small bony bridges, which are present
for instance in the skull /, are again resorbed, so that the
borders of the two bones may again be separated and an accretion
take place in both. _

Of peculiarities concerning the skull of the Elephant, besides
those already reported, we still may mention the fact that the tympanicum
furnishes part of the internal surface of the brain-cavity
(PI. 32 fig. 5, PI. 30 fig. 5). The (rather small) planes of the tympanicum
thus appearing on the inside of the braincase are situated
respectively below (behind) and before the plane belonging to the
petrosum, from which they are easily distinguished, the tympanicum
and petrosum being certainly already united in b, but the
limits of both being very well defined in b and 6j. — It is also
peculiar, that the deep furrow or imperfect bony canal, through
which the carotis interna makes its way into the brain-cavity, is
in the Elephant hollowed out in the tympanicum, not in the
petrosum.

Together with the adjoining parts of the petrosum the tympanicum
as usual articulates with the exoccipital. In the disconnected
tympano-petrosum (PI. 30 fig. 7) the tympanic cavity
is largely open on the plane adjoining the exoccipital, the opening
being surrounded with a bony frame formed partially of the
petrosum, partially of the tympanicum; the tympanic cavity here
communicates with the air-cavities in the exoccipital. At this large
opening also some air-cavities extend into the wall of the petrosum
. The walls of the tympanicum are likewise furnished with
air-sinuses from the tympanic cavity; on the contrary the squamosal
receives no air-sinuses from the tympanic cavity.

If we should in quite a few words express what is the most
characteristic in the Elephantine skull, we would say, that against
all general rules the skull during the postembryonal development
mainly grows not in length but in height. In this manner it is
attained, that it is easier for the animal to manage the heavy parts
— the tusks, the trunk —, which are placed at the anterior end,
the lever, at whose end they are situated, thereby being extraordinarily
shortened. At the same time the mighty molars are
pushed backwards as much as possible, which is also a considerable
alleviation. Through an enormous development of the air-
sinuses surrounding the small braincase the necessary planes are
produced for the attachment on the skull of the enormous masticatory
muscles and the muscles of the neck.

The skull appears to all intents as an outcome of the special
circumstances, under which it is placed, and the special claims
which are made to it. These might perhaps have been realised
also in other ways, but hardly more perfectly.

SOME REMARKS ON THE SKULL OF
THE AFRICAN ELEPHANT.

Plate 46.

At our disposal we had 4 skulls:

x, c. 55 cm long, is, judging from the wear of the teeth, the
youngest; it wears a tooth, which presumably is the dp3 (that is
to say the second of the six grinders of the Elephants); its anterior
end is already rather much worn, but all 7 plates, the last of which
is but a trace of a plate, can still be distinguished1; the first plate
is worn down to the base, but no part of the tooth has been
dropped. c?p4 has already come into use, but only the four anterior
plates have entered into wear.

y, c. 50 cm long. In this skull the dps has been so much worn
that the two anterior plates and most of the third are broken off.
dpi has to a much larger extent than in x come into use; the six
anterior plates have entered into wear (there are still two unworn2).

y' is a very defect skull, c. 60 cm long, the teeth of which
exhibit nearly quite the same figure as y.

i In the much younger skull b% the same suture is already wholly obliterated, the
occluse suture yet being distinctly seen on the upper surface.

1 Comp. Owen, Odontography p. 638.

2 According to Owen this tooth has only 7 plates.