is investigation of the Black Death, was
perhaps the first to give currency to the term.[295] Both the Black
Death and the Dancing Mania assumed the form of epidemics and the
latter, the Dancing Mania, was in his estimation the sequel of the
former, the Black Death. It was perhaps this similarity in the manner in
which they spread--the one by physical and the other by psychical
infection--that led him to speak of the spread of a popular delusion in
terms of a physical science. Furthermore, the hysteria was directly
traceable, as he believed, to the prevailing conditions of the time, and
this seemed to put the manifestations in the world of intelligible and
controllable phenomena, where they could be investigated.

It is this notion, then, that unrest which manifests itself in social
epidemics is an indication of pathological social conditions, and the
further, the more general, conception that unrest does not become social
and hence contagious except when there are contributing causes in the
environment--it is this that gives its special significance to the term
and the facts. Unrest in the social organism with the social ferments
that it induces is like fever in the individual organism, a highly
important diagnostic symptom.

b) _The crowd._--Neither Le Bon nor any of the other writers upon the
subject of mass psychology has succeeded in distinguishing clearly
between the organized or "psychological" crowd, as Le Bon calls it, and
other similar types of social groups. These distinctions, if they are to
be made objectively, must be made on the basis of case studies. It is
the purpose of the materials under the general heading of "The 'Animal'
Crowd," not so much to furnish a definition, as to indicate the nature
and sources of materials from which a definition can be formulated. It
is apparent that the different animal groups behave in ways that are
distinctive and characteristic, ways which are predetermined in the
organism to an extent that is not true of human beings.

One other distinction may possibly be made between the so-called
"animal" and the human crowd. The organized crowd is controlled by _a
common purpose_ and acts to achieve, no matter how vaguely it is
defined, a common end. The herd, on the other hand, has apparently no
common purpose. Every sheep in the flock, at least as the behavior of
the flock is ordinarily interpreted, behaves like every other. Action in
a stampede, for example, is collective bu