Among the phenomena observed in demonomaniacal hysteria there are some, as we have remarked, that modern neurologists have wished to _pass over in silence_, because it was impossible to give a rational explanation. It arose from that mysterious force which acts upon the human personality and its faculties and produces _supernatural results_ in contradiction to well known scientific laws, known in one sense as _Psychic Force_, but which is nothing else than _modern spiritualism_. This force, a power possessed in a high degree not only by hysterical persons, but all varieties of neuropaths, who are designated as _mediums_ by spiritual psychologists, _cannot be doubted by real scientists to day_. The demonologists of the Middle Ages have often mentioned it in the demonomaniacs, and attributed it to possession by evil spirits; and, if not pathologists, _they did not disdain to occupy themselves with something that tends to simplify the study of the physiology of the nervous system_; but to minds of the modern type, that consider science as synonymous with truth, it seems strange and incomprehensible that our learned investigators should have been overpowered by the fear of the criticism that might overtake them because _they cannot explain purely and simply an inexplicable fact, a truth, real positive and certain_. Not being ourselves timorous to this prudence, which is, they claim, one of the conditions, _sine qua non_, to be a candidate for the Institute of France, we shall now pursue our investigations with the historical documents regarding the medical Middle Age we possess, and thus loyally seek a scientific interpretation for facts observed in modern spiritualism or _psychic force_. Among these documents we will choose as a type the “Trial made to deliver a girl possessed by the Evil Spirit, at Louviers.” This suit, which dates back to 1591, is in reality a series of trials written up by several magistrates, in the presence of numerous witnesses, reporting with precision all facts observed by them—facts interpreted, it is true, with ideas of the demonidolatry of the sixteenth century, but having a character whose authenticity is undisputed, and _even undiscussed_. The first trial is thus conceived:[81] “On Saturday, the 18th day of August, 1591, in the morning at Louviers, in the aforesaid place, before us, Louis Morel, Councillor of the King, Provost General and Marshal of France for the Province of Normandy, holding Court in the service of the King in the villages and castles of Pont de l’Arche and Louviers, with one lieutenant, one recorder, and fifty archers, assisted by Monsieur Behotte, licentiate of law, Judge Advocate and Lieutenant General of Monsieur the Viscount of Rouen, in the presence of Louis Vauquet, our clerk.” * * *