t make sounds whilst indulging in "spasms of laughter." But their
distant cousin, the hyena, does laugh aloud, and its laughter agrees
with that of the dog and with the laughter of children and grown men
in simpler moods in that it is caused by the pleasurable emotion set
up by the imminent gratification of a healthy desire. The hyena
laughs, the dog grins and bounds, the child laughs and jumps for joy
at the approach of something good to eat. But it is a curious fact
that the whole attitude is changed when the food is within reach, and
the serious business of consuming it has commenced! Nor, indeed, is
the satisfaction which is felt after the gratification of appetite
accompanied by laughter. It seems that the display of the teeth by
drawing back the corners of the mouth, which is called a "grin," and
is associated in many dogs with a short, sharp, demonstrative bark,
and in mankind with the cackle we call a "laugh," is a retention, a
survival, of the playful, good-natured movement of gently biting or
pulling a companion with the teeth used by our animal ancestors to
draw attention to their joy and to communicate it to others. Gradually
it has lost the actual character of a friendly bite; the fore-feet or
hand pull instead of the teeth; the sound emitted has become further
differentiated from other sounds made by the animal. But the movement
for the display of the teeth, though no longer needed as a part of the
act of gripping, remains as an understood and universal indication of
joy and kindly feeling. So universal is it that this friendly display
of the teeth under the name "smile" is attributed to Nature, to
Fortune, and to deities by all races of men when those powers seem to
favour them.

Laughter is, then, in its essence and origin, a communication or
expression to others of the joyous mood of the laugher. There are many
and strangely varied occasions when laughter seizes on man, and it is
interesting to see how far they can be explained by this conception of
the primary and essential nature of the laugh, for many of them seem
at first sight remote from it. There is, first of all, the laughter of
revivification and escape from death or danger. After railway
accidents, earthquakes, and such terrible occurrences, those who have
been in great danger often burst into laughter. The nervous balance
has been upset by the shock (we call them "shocking accidents"), and
the emotional joy of escape, the joy of recovered lif