105
PHYSIOLOGICAL ÆSTHETICS.
periods exactly or very closely coincide with their own, in
which case a sympathetic vibration is set up and augmented
by the recurring impacts of the air-waves. In the labyrinth
of the ear we find sets of nervous structures which apparently
answer to each of these conditions. In its outer portion,
known as the vestibule, and in certain of its windings called
the ampullæ, are nervous terminations whose construction
leads us to suppose that they are readily excited in sympathy
with irregular agitations of short duration : and the sensa¬
tions aroused in connection with these stimulations are co^-
Ö
nized in the auditory centre as Noises. The deepest recess
of the labyrinth consists of a snail-shaped cavity known as
the cochlea, on whose walls are arranged an immense number
of small bodies, called after their discoverer Corti’s organs,
each of which, apparently, is capable of sympathetic vibration
only under the influence of a regular undulation whose
periodic recurrences closely coincide with its own natural
period. These bodies are connected with separate fibres, and
when the stimulations thus received are communicated to the
brain they are cognized as Musical Tones.
Again, air-waves of either class may differ in size, or, as
it is offener expressed, in amplitude of oscillation ; that is
to sa}r, in distance from crest to crest. Upon this objective
difference in the waves depends the subjective difference of
Loudness and its opposite. When the waves are very great
in size, the resulting sound is said to be very loud : as the
size diminishes, the sound becomes less and less. In short,
loudness is the subjective concomitant of intensity in stimu¬
lation. It does not depend upon the particular fibres excited,