brain centers which represent the most recent acquirements of the race are temporarily out of the circuit. If again we study the mind of the child, we find that it presents many points of likeness to the mind of the hypnotic subject and to the mind of the primitive man. We learn from biology that the child is to some extent a recapitulation of the life of the race, passing through in his individual development the stages of race development. Physiologically speaking, the higher brain centers and the centers for association, which are late acquirements of the race, are last developed in the child. We are therefore not surprised to find that the child, like the savage and the hypnotic subject, is imitative, impulsive, non-reflective, incapable of much abstract thought, deliberation or reasoning, and that he acts with a view to immediate rather than remote ends. If now we turn to the behavior of the normal adult man in mental epidemics and crazes of all kinds, from the Crusades to the Massacre of St. Bartholomew, from the tulip mania in Holland to the Dewey welcome in New York City, we observe that his behavior is to some extent similar to that of the hypnotic subject, and the child, and the primitive man. The general character of mental action in epidemics is as follows: Men become imitative beings and their actions are determined by suggestion from the actions of others. Memory and the association of ideas are inactive, and there is an inability to reason and an indisposition towards deliberation and calm reflection. Past experiences are disregarded, remote consequences are not seen and behavior is impulsive and spasmodic. Feeling is very strong and every kind of emotion is apt to be exaggerated. Calm observation is also lacking and mental images may be mistaken for objective reality, as in the case of the hallucinations that are frequent in these phenomena.