More than one learned physician, who have given their attestations to the existence of this most distressing complaint, have agreed that it actually occurs, and is occasioned by different causes. The most frequent source of the malady is in the dissipated and intemperate habits of those who, by a continued series of intoxication, become subject to what is popularly called the Blue Devils, instances of which mental disorder may be known to most who have lived for any period of their lives in society where hard drinking was a common vice. The joyous visions suggested by intoxication when the habit is first acquired, in time disappear, and are supplied by frightful impressions and scenes, which destroy the tranquillity of the unhappy debauchee. Apparitions of the most unpleasant appearance are his companions in solitude, and intrude even upon his hours of society; and when, by an alteration of habits, the mind is cleared of these frightful ideas, it requires but the slightest renewal of the association to bring back the full tide of misery upon the repentant libertine.

Of this the following story was told to the author by a gentleman connected with the sufferer. A young man of fortune, who had led what is called so gay a life as considerably to injure both his health and fortune, was at length obliged to consult the physician upon the means of restoring at least the former. One of his principal complaints was the frequent presence of a set of apparitions, resembling a band of figures dressed in green, who performed in his drawing-room a singular dance, to which he was compelled to bear witness, though he knew, to his great annoyance, that the whole corps de ballet existed only in his own imagination. His physician immediately informed him that he had lived upon town too long and too fast not to require an exchange to a more healthy and natural course of life. He therefore prescribed a gentle course of medicine, but earnestly recommended to his patient to retire to his own house in the country, observe a temperate diet and early hours, practising regular exercise, on the same principle avoiding fatigue, and assured him that by doing so he might bid adieu to black spirits and white, blue, green, and grey, with all their trumpery. The patient observed the advice, and prospered. His physician, after the interval of a month, received a grateful letter from him, acknowledging the success of his regimen. The green goblins had disappeared, and with them the unpleasant train of emotions to which their visits had given rise, and the patient had ordered his town-house to be dis-furnished and sold, while the furniture was to be sent down to his residence in the country, where he was determined in future to spend his life, without exposing himself to the temptations of town. One would have supposed this a well-devised scheme for health. But, alas ! no sooner had the furniture of the London drawing-room been placed in order in the gallery of the old manor-house, than the former delusion returned in full force ! the green figurantes, whom the patient's depraved imagination had so long associated with these moveables, came capering and frisking to accompany them, exclaiming with great glee, as if the sufferer should have been rejoiced to see them, " Here we all are—here we all are !" The visionary, if I recollect right, was so much shocked at their appearance, that he retired abroad, in despair that any part of Britain could shelter him from the daily persecution of this domestic ballet.

There is reason to believe that such cases are numerous, and that they may perhaps arise not only from the debility of stomach brought on by excess in wine or spirits, which derangement often sensibly affects the sense of sight, but also because the mind becomes habitually predominated over by a train of fantastic visions, the consequence of frequent intoxication ; and is thus, like a dislocated joint, apt again to go wrong, even when a different cause occasions the derangement.

It is easy to be supposed that habitual excitement by means of any other intoxicating drug, as opium, or its various substitutes, must expose those who practise the dangerous custom to the same inconvenience. Very frequent use of the nitrous oxide which affects the senses so strongly, and produces a short but singular state of ecstasy, would probably be found to occasion this species of disorder. But there are many other causes which medical men find attended with the same symptom, of embodying before the eyes of a patient imaginary illusions which are visible to no one else.

This persecution of spectral deceptions is also found to exist where no excesses of the patient can be alleged as the cause, owing, doubtless, to a deranged state of the blood, or nervous system.

The learned and acute Dr. Ferriar, of Manchester, was the first who brought before the English public the leading case, as it may be called, in this department, namely, that of Mons. Nicolai, the celebrated bookseller of Berlin. This gentleman was not a man merely of books, but of letters, and had the moral courage to lay before the Philosophical Society of Berlin an account of his own sufferings, from having been, by disease, subjected to a series of spectral illusions. The leading circumstances of this case may be stated very shortly, as it has been repeatedly before the public, and is insisted on by Dr. Ferriar, Dr. Hibbert, and others who have assumed Demonology as a subject. Nicolai traces his illness remotely to a series of disagreeable incidents which had happened to him in the beginning of the year 1791. The depression of spirits which was occasioned by these unpleasant occurrences, was aided by the consequences of neglecting a course of periodical bleeding which he had been accustomed to observe. This state of health brought on the disposition to see phantasmata, which visited, or it may be more properly said frequented, the apartments of the learned bookseller, presenting crowds of persons who moved and acted before him, nay, even spoke to and addressed him. These phantoms afforded nothing unpleasant to the imagination of the visionary either in sight or expression, and the patient was possessed of too much firmness to be otherwise affected by their presence than with a species of curiosity, as he remained convinced, from the beginning to the end of the disorder, that these singular effects were merely symptoms of the state of his health, and did not in any other respect regard them as a subject of apprehension. After a certain time, and some use of medicine, the phantoms became less distinct in their outline, less vivid in their colouring, faded, as it were, on the eye of the patient, and at length totally disappeared.