unknown, we naturally desire, when startled, to perceive the cause as
quickly as possible; and we consequently open our eyes fully, so that
the field of vision may be increased, and the eyeballs moved easily in
any direction. But this hardly accounts for the eyebrows being so
greatly raised as is the case, and for the wild staring of the open
eyes. The explanation lies, I believe, in the impossibility of opening
the eyes with great rapidity by merely raising the upper lids. To
effect this the eyebrows must be lifted energetically. Any one who will
try to open his eyes as quickly as possible before a mirror will find
that he acts thus; and the energetic lifting up of the eyebrows opens
the eyes so widely that they stare, the white being exposed all round
the iris. Moreover, the elevation of the eyebrows is an advantage in
looking upwards; for as long as they are lowered they impede our vision
in this direction. Sir C. Bell gives[1203] a curious little proof of
the part which the eyebrows play in opening the eyelids. In a stupidly
drunken man all the muscles are relaxed, and the eyelids consequently
droop, in the same manner as when we are falling asleep. To counteract
this tendency the drunkard raises his eyebrows; and this gives to him a
puzzled, foolish look, as is well represented in one of Hogarth s
drawings. The habit of raising the eyebrows having once been gained in
order to see as quickly as possible all around us, the movement would
follow from the force of association whenever astonishment was felt
from any cause, even from a sudden sound or an idea.
With adult persons, when the eyebrows are raised, the whole forehead
becomes much wrinkled in transverse lines; but with children this
occurs only to a slight degree. The wrinkles run in lines concentric
with each eyebrow, and are partially confluent in the middle. They are
highly characteristic of the expression of surprise or astonishment.
Each eyebrow, when raised, becomes also, as Duchenne remarks,[1204]
more arched than it was before.
The cause of the mouth being opened when astonishment is felt, is a
much more complex affair; and several causes apparently concur in
leading to this movement. It has often been supposed[1205] that the
sense of hearing is thus rendered more acute; but I have watched
persons listening intently to a slight noise, the nature and source of
which they knew perfectly, and they did not open their mouths.
Therefore I at one time imagined that the open mouth might aid in
distinguishing the direction whence a sound proceeded, by giving
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