What constitutes a crowd from the psychological point of view-A numerically strong agglomeration of individuals does not suffice to form a crowd-Special characteristics of psychological crowds-The turning in a fixed direction of the ideas and sentiments of individuals composing such a crowd, and the disappearance of their personality-The crowd is always dominated by considerations of which it is unconscious-The disappearance of brain activity and the predominance of medullar activity-The lowering of the intelligence and the complete transformation of the sentiments-The transformed sentiments may be better or worse than those of the individuals of which the crowd is composed-A crowd is as easily heroic as criminal.