ncing on his perch, and the canary by hopping and fluttering
about his cage with unwonted rapidity. Under emotions of an opposite
kind, animals equally display muscular excitement. The enraged lion
lashes his sides with his tail, knits his brows, protrudes his claws.
The cat sets up her back; the dog retracts his upper lip; the horse
throws back his ears. And in the struggles of creatures in pain, we see
that the like relation holds between excitement of the muscles and
excitement of the nerves of sensation.

In ourselves, distinguished from lower creatures as we are by feelings
alike more powerful and more varied, parallel facts are at once more
conspicuous and more numerous. We may conveniently look at them in
groups. We shall find that pleasurable sensations and painful
sensations, pleasurable emotions and painful emotions, all tend to
produce active demonstrations in proportion to their intensity.

In children, and even in adults who are not restrained by regard for
appearances, a highly agreeable taste is followed by a smacking of the
lips. An infant will laugh and bound in its nurse's arms at the sight of
a brilliant colour or the hearing of a new sound. People are apt to beat
time with head or feet to music which particularly pleases them. In a
sensitive person an agreeable perfume will produce a smile; and smiles
will be seen on the faces of a crowd gazing at some splendid burst of
fireworks Even the pleasant sensation of warmth felt on getting to the
fireside out of a winter's storm, will similarly express itself in the
face.

Painful sensations, being mostly far more intense than pleasurable ones,
cause muscular actions of a much more decided kind. A sudden twinge
produces a convulsive start of the whole body. A pain less violent, but
continuous, is accompanied by a knitting of the brows, a setting of the
teeth or biting of the lip, and a contraction of the features generally.
Under a persistent pain of a severer kind, other muscular actions are
added: the body is swayed to and fro; the hands clench anything they can
lay hold of; and should the agony rise still higher, the sufferer rolls
about on the floor almost convulsed.

Though more varied, the natural language of the pleasurable emotions
comes within the same generalisation. A smile, which is the commonest
expression of gratified feeling, is a contraction of certain facial
muscles; and when the smile broadens into a laugh, we see a more violent
and mo