The psychology of crazes is clearly seen in certain of its aspects in the homicidal manias that have swept over communities or whole countries at frequent intervals in the world’s history. The homicidal impulse itself is one of the most primitive and basal of all impulses. The reason for this is apparent. The history of man has been a history of warfare and of struggle for existence. It has been man against man, tribe against tribe, nation against nation. Habits like these are not quickly unlearned, and reversion to them in times of social disturbance is not strange. In the massacre of St. Bartholomew we have a typical instance of the homicidal mania. The necessary conditions were, first, great emotional excitement caused by religious fanaticism acting as an inhibitory agent upon the higher brain centers and allowing the primitive impulses to act unchecked; second, the removal of external and customary restraints, effected in this case by the royal decree; and third, the mental effects of imitation and suggestion. These conditions being all supplied, the French people resolved themselves speedily into assassins and cut-throats, and enjoyed a homicidal debauch. Begun in Paris, the massacre spread in true epidemic form throughout France, until fifteen or twenty thousand people had perished. These homicidal manias have, of course, been very frequent in history. The decivilizing influence of the craze is, however, most perfectly illustrated in the various scenes of the French Revolution. Here the overturning of the social and religious order itself acted in part as the unsettling and emotionally exciting cause. The usual results followed. The effect of social excitement in paralyzing the intellect was shown in this case in the wholesale and useless destruction of women and children. Furthermore, this reversion to the manners of the savage carries with it its appropriate mood. The slaughterers are not like demons, as we imagine demons to be, but rather like thoughtless children. There is merriment and much gayety, and there is dancing and singing around the corpses, and seats are arranged for the ladies, who are eager to enjoy the spectacle; and finally the victims are made to pass through a double row of executioners, who carve them into pieces gradually, so that all can saturate themselves with the sight of the bloodshed.