course, and even by those aspects of nature--for
instance, blue open sky or overhanging mountains--which naturally call
up in us the physical manifestation of emotional states. The coercive
force with which our surroundings--animate or inanimate--compel us to
adopt the feelings which are suggested by their attitudes, forms, or
movements, is perhaps as a rule too weak to be noticed by a
self-controlled, unemotional man. But if we want an example of this
influence at its strongest, we need but remember how difficult it is for
an individual to resist the contagion of collective feeling. On public
occasions the common mood, whether of joy or sorrow, is often
communicated even to those who were originally possessed by the opposite
feeling. So powerful is the infection of great excitement
that--according to M. Fere--even a perfectly sober man who takes part in
a drinking bout may often be tempted to join in the antics of his
drunken comrades in a sort of second-hand intoxication, "drunkenness by
induction." In the great mental epidemics of the Middle Ages this kind
of contagion operated with more fatal results than ever before or
afterward. But even in modern times a popular street riot may often show
us something of the same phenomenon. The great tumult in London in 1886
afforded, it is said, a good opportunity of observing how people who had
originally maintained an indifferent attitude were gradually carried
away by the general excitement, even to the extent of joining in the
outrages. In this instance the contagious effect of expressional
movements was undoubtedly facilitated by their connection with so
primary an impulse as that of rapine and destruction. But the case is
the same with all the activities which appear as the outward
manifestations of our strongest feeling-states. They all consist of
instinctive actions with which everyone is well familiar from his own
experience. It is therefore natural that anger, hate, or love may be
communicated almost automatically from an individual to masses, and from
masses to individuals.

Now that the principle of the interindividual diffusion of feeling has
been stated and explained, we may return to our main line of research
and examine its bearings on the expressional impulse. We have seen that
in the social surroundings of the individual there is enacted a process
resembling that which takes place within his own organism. Just as
functional modifications spread from organ to o