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103

The nasal cavity.

The nasal cavity.

104

Elephant Chang, blunt in the other specimens examined), which
lies at the base of a thick downward and caudad projection of
the mucous membrane, above which the entrance to the sinus
maxillaris has its place. To a low oblique longitudinal crest on
the bony nasoturbinal is appended a large and thick cartilaginous
plate, which forms a continuation of it and is connected with it
through a narrow stripe of connective tissue. The mucous membrane
investing the bony nasoturbinal is directly continued over
the median side of the said cartilage and forms a smooth even
surface. The ventral margin of the caudal half of the cartilage
is free and the mucous membrane here passes beyond the margin
and is continued on the lateral surface of the cartilage and
further curves on to the lateral wall of the nasal cavity. The
mucous membrane then forms a large nasad closed diverticulum
between the cartilage and the nasal wall, the blind end of which
extends nasad considerably beyond the cartilage (PI. 38 figs. 2—3).
On the lateral nasal wall, nearly on a level with the ventral margin
of the cartilage, a fold of the mucous membrane arises, which
extends rostrad, successively increasing in height, and finally twins
up to the lateral surface of the cartilage. From this point to the
bottom of the diverticulum it has in the old Elephant Chang a
length of c. 12 cm, whilst the height is c. 10 and the breadth
c. 6 cm. The medial wall of the diverticulum invests the cartilage
, the ventral and lateral walls resp. the pars dentalis and
ascendens of the intermaxillary bone. The dorsal wall is mostly
separated from the nasal bone through a thick la}^er of connective
tissue containing a venous plexus. At the nasal end of the diverticulum
there are one or two openings forming the entrance to
the air-sinus in the nasal bone.

Rostrad the cartilaginous plate in question runs into the cartilaginous
sheet investing the inner side of the anterior part of the
nasal bones, also the rostral end of the bony nasoturbinal is continuous
with the same cartilaginous sheet, which in the median
line is continuous with the cartilaginous septum nasi.

The latter extends rostrad a little beyond the tip of the nasal
bones; it terminates above the supreme point of the intermaxillary,
where the anterior and posterior side of that bone meet. At this
point the median margin of the two large, vaulted cartilaginous
nasal wings (PI. 40 fig. 1) is connected with it; only the posterior
half of that margin is confluent with the septum; the anterior
half of it is quite free, the two nasal wings here being only
through connective tissue connected with one another. The outer
margin is quite free. The medial part of the posterior margin
of the cartilaginous wing is continued into the cartilaginous investment
of the inner side of the nasal bones, while the rest of
the posterior margin is free.

If we compare the above described facts found in the Elephant
with the general find in Mammals, we cannot doubt that
the remarkable thick cartilage, appended to the bony nasoturbinal,
is really a specially developed and partially emancipated part of
the cartilaginous nasoturbinal. The projection of the mucous membrane
, in the base of which the small projection of the bony nasoturbinal
is situated, is evidently the downward process of the nasoturbinal
extending into the opening of the maxillary sinus, which
opening is also in the Elephant intimately connected with it; only
the bone in it is not so well developed as usual.

The little cartilage in the cushion mentioned above (p. 101)
we cannot imagine to be anything but a separate part of the cartilaginous
crest which we find in the anterior part of the nasoturbinal
of other Mammals and which may sometimes be partly
disintegrated in small separate cartilaginous bodies.

The septum between the nasal tubes is in different parts of
different thickness. In the free proboscis it is tolerably thick (see
PI. 14 fig. 2 in the First Part of this work). Where the cushionlike
thickening of the wall is developed, the septum is as thin as
paper (PI. 41 fig. 4). At the upper end of that part of the nasal
cavity which is surrounded by bone, where the septum incloses
the cartilaginous median plate, the distance between the two tubes
is considerable, the septum cartilagineum is here very thick (PI.
41 fig. 6); farther caudad the septum is again thinner, and in the
vicinity of the inferior (caudal) margin, where no solid parts are
present any more, it is again rather thin.

The significance of the special arrangements in the nasal
cavity of the Elephant are presumably the following.

When the tip of the proboscis is put down into water and
the muscular fascicles of the cushion contract, the water must
ascend in the nasal tubes; at the same time perhaps a feeble
suction takes place by means of the lungs. The water ascends
scarcely farther than to the uppermost point of the intermaxillary,
the nasal tubes here forming a considerable angle and being rather
narrowed.

Of the significance of the marvellous large rigid cartilaginous
plate on the lateral side of the nasal cavity it is more difficult to
form a conception. We venture the supposition that it is the cause
of the flourishes, which the Elephant sets up: the air being vigorously
expelled through the nasal cavity it meets the margin of
the plate, which is set vibrating.