'The nerves are easily excited into movement by an infinite variety of external impulses, or internal agitations. By whatever impulse any motion, vibration, or affection, in the nervous system is produced, a correspondent sensation, or train of sensations, or ideas in the mind, will naturally follow. When the body is in regular health, and the operations of the mind are in a natural and healthful train, the action of the nervous system, being affected only by the regular and successive impressions made upon it by the objects of nature, as they successively occur, will present to the mind just and true images of the scenes that surround it. But by various species of infirmity and disorder in the body, the nerves, sometimes in their entire system, and sometimes only in those divisions of them which are attached to particular organs of sense, may be subjected to very irregular motions or vibrations. Hence unreal images may be raised in the mind. The state of the nervous affections may be vitiated by intemperate indulgence, or by infirmity resulting from sedentary and melancholy habits. Superstitions, fancies, or enthusiastic emotions, do often greatly disturb the regular action of the nervous system. Such elastic and vibratory strings may be subject to an infinite variety of irregular movements, sometimes in consequence of a disordered state of health, and sometimes arising from peculiarity of constitutional structure, which may present false and often fantastic images to the mind. No cause, perhaps, produces a more anomalous oscitancy, or vibration of the nervous system, or of some particular portions of it, than habits of intemperate indulgence. And I have not unfrequently become acquainted with men who had been addicted to such excesses, who were troubled with apprehensions of supernatural apparitions. A peculiar imbecility of constitution, however, created by study, retirement, or other causes, may be productive of similar effects, and sometimes these nervous anomalies are formed in men who are otherwise of active and athletic constitutions. But where they possess enlightened minds and vigorous understandings, such visionary tendencies may be counteracted by their intellectual energies. Yet have we sometimes known the strongest understandings overcome by the vivacity of nervous impression, which frequently is scarcely inferior to the most lively ideas of sense. This may, especially, be the case in two opposite conditions; either when the body has fallen into a gloomy temperament, and the mind is weakened by fears, in which case it is oppressed by distressing apprehensions; or, on the other hand, when the nerves, the primary organs, of sensation, are strained into an unnatural tension, and the whole system is exalted by an enthusiastic fervor to the pitch of delirious intoxication. When a man is exalted to such a degree of nervous excitement and mental feeling, his visions are commonly pleasing, often rapturous, and sometimes