You have not, perhaps, remarked that in the act of swallowing, something
rises and contracts itself at the same moment in your throat, producing
a kind of internal convulsion which jerks whatever is inside. People
do not think about it when they are eating, because it is an involuntary
action, and their attention is otherwise engaged.

But try to swallow when there is nothing in your mouth, and you will
perceive what I mean at once.

Now, imagine our lobby at the back of the throat as a small closet,
with a doorway in its wall, half-way up, the doorway being closed by
a curtain. In the ceiling is a hole, which leads to the nose; in the
floor two large tubes open out; the front one leading to the lungs,
the one behind, to the stomach.

Now swallow, and I will tell you what happens. The curtain rises up
and clings to the ceiling, and thus the passage to the nose is stopped
up. The lung-tube rises along the wall, and hides itself under the
door, contracting itself, and making itself quite small, as if it
wished to leave plenty of room for the mouthful of food which is about
to pass over it; and, for still greater security, at the very moment
it rises, it pushes against a small trap-door which shuts up its mouth.
No other road remains, therefore, but through the tube which leads to
the stomach; the pulpy mouthful drops straight therein, without risk
of mistake, and when it is once there, everything readjusts itself as
before.

These are very ingenious contrivances, and I will venture to say that
if we would but study the wonders of the marvellous and varied machinery