ly a social appeal and response. Only in rare cases do people
laugh when they are alone. Under conditions which in the presence of
others would cause them to laugh they only "chuckle" or smile, and
may, though ready to burst into laughter, not even exhibit its minor
expressions when alone. On the other hand, some sane people have the
habit of laughing aloud when alone, and there is a recognised form of
idiocy which is accompanied by incessant laughter, ceasing only with
sleep. Then there is that peculiar condition of laughter which is
called "giggling," which is laughter asserting itself in spite of
efforts made to restrain it, and frequently only because the occasion
is one when the "giggler" is especially anxious not to laugh. This
kind of "inverted suggestion," as in the case where an individual
"blurts out" the very word or phrase which he is anxious not to use,
is obviously not primitive, but connected with the long training and
drilling of mankind into approved "behaviour" by "taboos" and
restrictive injunctions. Efforts to behave correctly, by causing
anxiety and mental disturbance in excitable or so-called "nervous"
subjects, lead to an over mastering impulse to do the very thing which
must not be done!

It seems that laughter has its origin far back in the animal ancestry
of man, and is essentially an expression to others of the joy and
exhilaration felt by the laugher. It is an appeal through the eye and
ear for sympathy and comradeship in enjoyment. Its use to social
animals is in the binding together of the members of a group or
society in common feeling and action. Many monkeys laugh, some of them
grinning so as to show the teeth, partly opening the mouth and making
sounds by spasmodic breathing, identical with those made by man. I
have seen and heard the chimpanzees at the Zoological Gardens laugh
like children at the approach of their friend and my friend, the
distinguished naturalist, Mr. George Boulenger, F.R.S., recognising
him among the crowd in front of their cage when he was still far off.
And I have often made chimpanzees laugh--"roar with laughter," and
roll over in excitement--by tickling them under the arms. The saying
of Aristotle (inscribed over the curtain of the Palais Royal Theatre
in Paris) that "Laughter is better than tears, because laughter is the
speciality of man," is not true. Not only do the higher apes and some
of the smaller monkeys laugh, but dogs also laugh, although they do
no