In a large number of cases such phenomena appear in connection with persons who suffer of some nervous disease, and then the knockings are, of course, produced unconsciously, and may be accompanied by evidences of exceptional powers. It need not be added, however, that the two symptoms are not necessarily of the same nature; generally the mechanical knockings precede the development of ecstatic visions. A girl of eleven years, the child of humble Alsatian parents, presented, in 1852, this succession of symptoms very strikingly. The child had a habit of falling asleep at all hours; at once mysterious knockings began to perform a dance or a march, and continued daily for more than an hour. After some time the poor girl began, also, to talk in her sleep, and to converse with the knocking agent. She would order him to beat a tattoo, or to play a quickstep, and immediately it was done. The directions of bystanders, even when not uttered but merely formed earnestly in their mind, were obeyed in like manner. Finally the child, getting no doubt worse and unmercifully excited by the crowds of curious people who thronged the house, began to admonish her audience, and to preach and pray; during these exhortations no knockings were heard, but she became clairvoyant and recognized all the persons present, even with her eyes closed. She fancied that a black man with a red shawl produced the knockings and delivered the speeches. Her clairvoyance became at last so striking that her case excited the deepest interest of persons in high social position, and several physicians examined it with great care. Her disease was declared to be neurosis coeliaca ("Magicon," v. 274).