ridges correspond on
the opposite side. The outer eminence is called helix. Within the
body of the cartilage arises a forked eminence called antihelix,
which terminates in a small and short tongue called antitragus. The
remaining part of the ear, called the concha or shell, is anteriorly
hollow, but posteriorly convex, growing gradually deeper; with a
crooked line or ridge running along its middle, which is immediately
joined to the meatus auditorius, or entrance into the ear; before
which stands a round moveable appendix, which serves as a defense,
called tragus.

Against this funnel of the ear the sonorous waves strike, and its
different parts are most admirably contrived to reflect them all into
the meatus auditorius: if it would not occupy too much time, it might
be shown, that all these curves and spirals are contrived in the best
manner possible, and with a most perfect knowledge of the geometry of
sounds, to reflect the sonorous pulses accurately, and in the
greatest possible quantity, into the ear.

This external part of the ear is differently formed in different
animals; and admirably suited to their various situations and habits.
In man it is close to the head, but so formed as to collect the
various pulses with great accuracy; in other animals it is more
simple, where less accuracy is required, but it is, in general, much
larger, having the appearance of an oblong funnel; and this gives
them a greater delicacy of hearing, which was necessary for them.

In animals which are defenceless and timid, and which are constantly
obliged to seek their safety in flight, the opening of this funnel is
placed behind, that they may better hear the noises behind them. This
is particularly instanced in the hare. Beasts of prey have this
opening before, that they may more easily discover their prey; as the
lion and tiger. Those that feed on birds have the opening directed
upwards, as the fox; and it is inclined downwards in animals, such as
the weasel, which seek their prey on the earth.

To this external part of the ear, which I have described, is
connected the meatus auditorius, or passage to the internal ear,
which is somewhat of a compressed cylindrical figure, lessening as it
bends inwards: a considerable part of it is bony, and it is bent
towards the middle. Across this passage, at its inner extremity, is
stretched a thin membrane, called membrana tympani. Upon the surface
of this membrane, the sonorous waves, whic