effect produced upon the sympathetic nerve, or rather the system of
nerves termed respiratory. These communicate with every organ affected
in mirth, but the ultimate connection between mind and body is hidden
from our view.

In all laughter there is more or less pleasure, except in that of
hysteria, when by a sudden shock the course of Nature is reversed, and
excessive grief will produce the signs of joy, as extravagant delight
will sometimes exhibit those of sorrow. We should also exclude the
laughter caused by inhalation of gas, and that of maniacs, which arising
from some strange and unaccountable feeling is abnormal and imperfect,
and known by a hollow sound peculiar to itself. None of these kinds of
laughter are primary, they are but imperfect reflections of our usual
modes of expression, and, excepting such cases, we may agree that M.
Paffe is correct in observing that "Joy is an indispensable condition of
laughter." Dr. Darwin refers to the laughter of idiots to prove that it
may be occasioned by pleasure alone. Strangely enough, he quotes as an
instance in point the fact of an idiot boy having laughed at receiving a
black eye.

Proceeding onwards, we next come to inquire why the sense of humour is
expressed by voice and countenance, and does not merely afford a silent
and secret delight? The answer may be given, that one object, at least,
is to increase social communication and multiply pleasure. The
well-being of the animal world largely depends upon the power of each
member of it to communicate with others of the same species. They all do
so by sound and gesture, probably to a larger extent than we generally
imagine. A celebrated physician lately observed to me that "all animals
have some language." How far mere signs deserve so high a name may be
questioned. But man has great powers of intercourse, and it is much