s energy in
sudden thoughts and feelings. If, when walking along, there flashes on
you an idea that creates great surprise, hope, or alarm, you stop; or if
sitting cross-legged, swinging your pendent foot, the movement is at
once arrested. From the viscera, too, intense mental action abstracts
energy. Joy, disappointment, anxiety, or any moral perturbation rising
to a great height, will destroy appetite; or if food has been taken,
will arrest digestion; and even a purely intellectual activity, when
extreme, will do the like.

Facts, then, fully bear out these _a priori_ inferences, that the
nervous excitement at any moment present to consciousness as feeling,
must expend itself in some way or other; that of the three classes of
channels open to it, it must take one, two, or more, according to
circumstances; that the closure or obstruction of one, must increase the
discharge through the others; and conversely, that if to answer some
demand, the efflux of nervous energy in one direction is unusually
great, there must be a corresponding decrease of the efflux in other
directions. Setting out from these premises, let us now see what
interpretation is to be put on the phenomena of laughter.

* * * * *

That laughter is a display of muscular excitement, and so illustrates
the general law that feeling passing a certain pitch habitually vents
itself in bodily action, scarcely needs pointing out. It perhaps needs
pointing out, however, that strong feeling of almost any kind produces
this result. It is not a sense of the ludicrous, only, which does it;
nor are the various forms of joyous emotion the sole additional causes.
We have, besides, the sardonic laughter and the hysterical laughter,
which result from mental distress; to which must be added certain
sensations, as tickling, and, according to Mr. Bain, cold, and some
kinds of acute pain.

Strong feeling, mental or physical, being, then, the general cause of
laughter, we have to note that the muscular actions constituting it are
distinguished from most others by this, that they are purposeless. In
general, bodily motions that are prompted by feelings are directed to
special ends; as when we try to escape a danger, or struggle to secure a
gratification. But the movements of chest and limbs which we make when
laughing have no object. And now remark that these quasi-convulsive
contractions of the muscles, having no object, but being results of