Freiburger historische Bestände - digital

113

The ethmoid and the pneumatic sinuses.

The pneumatic sinuses.

114

The sinus 7' has been reduced to a small bulla, a little larger
than a pea, raising slightly from the bottom of the sinus 6'.

The sinus 8' is very large and mainly behaving as the corresponding
one in the left half; only in its rostral part it has
been somewhat restricted by the expansion of the sinus 3 a'.

The sinus 8 a has been reduced to a very small sinus lying
deep down in the frontale, exactly dorsally to the ethmoid and
not reaching to the surface.

The sinus IV is a small sinus of two compartments in the
ventral part of the pars orbitalis of the frontale, ventrally to the
sinus 6 a'.

The sinus 15' likewise is a small sinus of two compartments,
it is a little larger than the preceding and lies in the frontale,
ventrally to this latter.

The sinus 23' is a little narrow sinus ventrally in the pre-
sphenoid, completely covered by the two preceding sinuses.

The sinus 25' and 26' are like those of the left side.

The sinus V and Va' are mainly as the corresponding sinuses
in the left side but for the sinus Va' being so large that it extends
into the left half (see left sinus Va').

The sinus Va" is a little irregular sinus in the dorsal part of
the presphenoid, where it lies medially and dorsally to the foramen
opticum.

The sinus Va'" is a bulla a little larger than a pea arching
into the sinus Va'.

In the furrow-shaped depression on the lateral wall of the
nasal cavity (see above) is found the aperture of the sinus max-
illaris, which is in the main like that of the left side, yet it does
not caudally extend as far in the pars orbitalis as the corresponding
sinus; here it borders on the sinus 4' and 6a'.

The sinus intermaxillaris inferior essentially like that of the
left side; only caudally it extends a little farther than the other one.

The sinus nasalis mainly as that of the left side.

The aperture of the sinus intermaxillaris superior is not sharply
outlined in its nasal circumference and the sinus is almost only
half as large as the left one.

The pneumatic sinuses derived from the cavum tympani are
mainly like those of the left side.

Elephant h.

Left half of the skull (PI. 28 fig. 2, PI. 29 figs. 5 and 6, PI. 42
figs. 1—3, PI. 44 figs. 1—3, PI. 45 fig. 3).

The system of the pneumatic sinuses issuing from the ethmoid
is as follows:

In the caudal arched part of the nasoturbinale there are two
small sinuses, the sinus F and a ventral and a dorsal one,
both rather low, but especially the ventral one somewhat broad.
The apertures are lying on the lateral side of the nasoturbinale.
In the rostral part of the nasoturbinale there is a flat, triangular
sinus with the aperture on the lateral side of the nasoturbinale,
a little rostrad to the aperture of the sinus I'. Dorsally to the
triangular sinus there is another, smaller sinus expanding a little
laterally in the frontale and covered by the sinus nasalis; its aperture
is situated between the nasoturbinal and the 1. ectoturbinal.

The sinus 1' is a smaller sinus at the bottom of the frontale,
completely covered by the sinus nasalis.

The sinus 1 a, the aperture of which is lying a little ventrally
to that of the preceding sinus, is somewhat larger than and laterally
placed to the sinus 1' in the frontale; it is completely covered
by the sinus nasalis.

The sinus 2' and sinus 3' are two quite small sinuses in
the frontale, completely covered by the sinus 4'.

The sinus V is large and has several compartments, it is lying
in the frontale and intermaxillare. It extends in the frontale right
on to the dorsal plane of the skull and here occupies a part which
in the Elephant c is occupied by the lateral part of the sinus 6'
and 8 a'. From the frontale the sinus 4' extends rostrad into the
intermaxillare, where it takes up the place, which in c is occupied
by the sinus intermaxillaris sup. and a lateral part of the sinus
intermaxillaris inf., so that the sinus 4' reaches right on to the
sinus maxillaris. The sinus 4' at the same time expands ventrally
in the frontale in a large multilocular section, whose anterior part
occupies a considerable part of the pars orbitalis and borders rostrad

on the sinus maxillaris, caudad on the sinus 8'; ventrally it extends
to the sinus 15'. The sinus 4' sends a rather broad but flat elongation
into the lacrymale.

The sinus 6' is at its origin a narrow canal running in caudad
direction beneath the sinus nasalis, then it inclines medially, expanding
like a broad, quite flat compartment constantly below
the sinus nasalis; at last, mediad to the prolongation from this
sinus (see below), it reaches right to the septum sinuum and then
expands as a large sinus, divided into many small compartments
in the frontale and parietale. It extends caudad along the septum
(which is winding irregularly) but at the same time expands laterally
, especially in its rostral part, which is wedged in between
the sinuses 8' and 4' and the sinus nasalis, covering the caudal
prolongation from the lastnamed sinus, and whilst the sinus 6'
here only obtains a depth of 7 cm it has close by the septum
a depth of 15 cm.

The sinus 7' is a quite small sinus, completely covered by
the sinus nasalis.

The sinus 8' is an enormously large sinus. It extends to the
dorsal plane of the skull laterally and caudally to the sinus 6',
o: it pneumatizes the rest of the frontale and the greater part of
the parietale, where it obtains a depth of 18 cm. It expands
further down into the occipitale, where it occupies by far the
greater part; only ventro-laterally a little section is pneumatized
by the sinus occipitalis. The sinus 8' also extends down into the
lateral plane of the skull, where it expands in the caudal part of
the frontale, in the parietale, and from there down into the squamosum
; here it almost encloses the meatus acusticus externus
(except ventrally, where there is still a longitudinal fissure to be
found in the meatus) and is here of a depth of 10 cm; the sinus
at the same time extends into the proc. zygomaticus. From the
naso-ventral part of the squamosum the sinus expands into the
basisphenoid, and from there down into the proc. pterygoideus,
where it does not, however, obtain any very considerable compass
, as it is essentially limited to the root of this processus. All
this sinus is divided into a great many small compartments; only
in a few places, in the squamosum, in the proc. zygomaticus and
in the ventral part of the occipitale there are also a few larger
compartments. The sinus is divided into two large sections, a
dorsal one, in expansion almost corresponding to the sinus 7' in
Elephant c, and a ventral one, almost corresponding to the sinus 8';
between these two the sutura squamosa, which has the shape of
a high and thin bony lamella, forms a septum, but rostrad to this
suture and right down at the bottom of the sinus the two sections
are communicating through a narrow opening. In the dorsal section
of the sinus 8' there is a system of consolidating bony lamellae;
9 of them are primary, o: lamellae reaching from the bottom to
the top and extending radially from the periphery of the sinus
towards its rostral part. 1.—4. lamellae, which are lying dorsally,
extend farthest into the sinus; the rest of the lamellae issue from
the ventral part of the sinus and from the sutura squamosa. Although
this number of primary lamellae corresponds to that found
in Elephant c, there is, however, so much difference in their distribution
that they cannot at once be looked upon as homologous.
These primary lamellae are of peculiar appearance: they are folded,
and may be compared with the waves of a piece of corrugated
iron, only with the modification that the folds of the lamellae are
more irregular and more or less angular; they expand infundi-
buliform towards the surface of the skull, and these funnels are
open at the bottom. On the way towards the surface the borders
of one wave or of two neighbouring waves approach each other
and coalesce; in this way another smaller compartment is formed,
likewise open at the bottom; it expands farther on towards the
surface with a wavy plane; through a continued coalescing of the
wavy borders this smaller compartment is divided into still smaller
ones a. s. f. To these are to be added rampant arches all reaching
to the surface and extending partly between the waves of one
lamella, partly between two neighbouring lamellae. These arches
are of different height; in the specimen at hand they were found
in four different heights, the lowest, 2—3 cm high, next to the surface
, whilst the highest could be reaching down to a few centimeters
from the bottom. Through these ramping arches and the
coalescing of the folds of the lamellae the numerous small com-