express it physiologically, the unusual excitement in the lower centers of the brain accompanying excessive emotion may not only find expression in muscular movements, but may also exercise an inhibitory or paralyzing effect upon the higher centers, resulting in a kind of hypnotic condition. Neither is it difficult to understand the presence of this excessive emotion during mental epidemics or during any purely social movements, when we remember that war itself is the great original social movement, which even in this age always takes the form of a mental epidemic called the war spirit. The emotional effect of the mere physical congregation of a large number of men, the emotion increasing with the size of the assemblage, is known to all. As we glance now at a few of the typical mental epidemics of history, we shall notice the ever-recurring presence of some or all of the mental and moral traits that I have pointed out. For illustrations of these phenomena we may turn indifferently to ancient, medieval or modern history. They abound at every period. Very good examples may be found in Hecker’s ‘Epidemics of the Middle Ages.’ In the Crusades, particularly in the Children’s Crusades, we may observe all the mental, moral and physical peculiarities that have been mentioned. In the anti-Semitic mania, we see in its history of criminal horror the dehumanizing effects of the epidemic and the moral reversion which takes place under the influence of social excitement. The peculiar physical phenomena which have been referred to as characterizing epidemic excitement are best illustrated in the dancing manias of the Middle Ages and in the religious revival. Although epidemic ‘revivals’ have occurred in all countries, some of the best illustrations are seen in America in its early history and to some extent at the present day. At the time of the elder Edwards, revivals were accompanied by fainting, falling, tremor and numbness. In the Kentucky revivals the meetings, called camp meetings, were held in the open air. The interest in them spread in true epidemic form. At the height of the excitement, as many as 20,000 people, men, women and children, were gathered in a single camp at one time. Dr. Davidson, who writes a history of this revival, says that “the laborer quitted his task, age snatched his crutch, youth forgot his pastime, the plough was left in the furrow, business of all kinds was suspended, bold hunters and sober matrons, young men, maidens and little children flocked to the common center of attraction.” The emotional tension was very great. A boy perhaps would spring to his feet and begin to rave, or some over-excited person would utter a piercing shriek, or a cry of triumph, and this would be the signal for a general hysterical outbreak, accompanied by many remarkable physical symptoms. Of these the most common were falling in convulsive spasms, jerking, dancing, barking like dogs, fainting, crying, singing, praying and cursing.