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210
The Fairy-Land of Science
·
Arabella B. Buckley
124
On
the
other
side
of
this
membrane,
inside
the
ear,
there
is
air,
which
fills
the
whole
of
the
inner
chamber
and
the
tube,
which
runs
down
into
the
throat
behind
the
nose,
and
is
called
the
Eustachian
tube
after
the
man
who
discovered
it.
This
tube
is
closed
at
the
end
by
a
valve
which
opens
and
shuts.
If
you
breathe
out
strongly,
and
then
shut
your
mouth
and
swallow,
you
will
hear
a
little
"click"
in
your
ear.
This
is
because
in
swallowing
you
draw
the
air
out
of
the
Eustachian
tube
and
so
draw
in
the
membrane,
which
clicks
as
it
goes
back
again.
But
unless
you
do
this
the
tube
and
the
whole
chamber
cavity
behind
the
membrane
remains
full
of
air.
Now,
as
this
membrane
is
driven
to
and
fro
by
the
sound-waves,
it
naturally
shakes
the
air
in
the
cavity
behind
it,
and
it
also
sets
moving
three
most
curious
little
bones.
The
first
of
the
bones
is
fastened
to
the
middle
of
the
drumhead
so
that
it
moves
to
and
fro
every
time
this
membrane
quivers.
The
head
of
this
bone
fits
into
a
hole
in
the
next
bone,
the
anvil,
and
is
fastened
to
it
by
muscles,
so
as
to
drag
it
along
with
it;
but,
the
muscles
being
elastic,
it
can
draw
back
a
little
from
the
anvil,
and
so
give
it
a
blow
each
time
it
comes
back.
This
anvil
is
in
its
turn
very
firmly
fixed
to
the
little
bone,
shaped
like
a
stirrup,
which
you
see
at
the
end
of
the
chain.
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