us in being
present at a play, or in reading a romance, some persons are so totally
absorbed as to forget their usual time of sleep, and to neglect their
meals; while others are said to have been so involved in voluntary study as
not to have heard the discharge of artillery; and there is a story of an
Italian politician, who could think so intensely on other subjects, as to
be insensible to the torture of the rack.

From hence it appears, that these catenations of ideas and muscular
motions, which form the trains of reverie, are composed both of voluntary
and sensitive associations of them; and that these ideas differ from those
of delirium or of sleep, as they are kept consistent by the power of
volition; and they differ also from the trains of ideas belonging to
insanity, as they are as frequently excited by sensation as by volition.
But lastly, that the whole sensorial power is so employed on these trains
of complete reverie, that like the violent efforts of volition, as in
convulsions or insanity; or like the great activity of the irritative
motions in drunkenness; or of the sensitive motions in delirium; they
preclude all sensation consequent to external stimulus.

2. Those persons, who are said to walk in their sleep, are affected with
reverie to so great a degree, that it becomes a formidable disease; the
essence of which consists in the inaptitude of the mind to attend to
external stimuli. Many histories of this disease have been published by
medical writers; of which there is a very curious one in the Lausanne
Transactions. I shall here subjoin an account of such a case, with its
cure, for the better illustration of this subject.

A very ingenious and elegant young lady, with light eyes and hair, about
the age of seventeen, in other respects well, was suddenly seized soon
after her usual menstruation with this very wonderful malady. The disease
began with vehement convulsions of almost every muscle of her body, with
great but vain efforts to vomit, and the most violent hiccoughs, that can
be conceived: these were succeeded in about an hour with a fixed spasm; in
which one hand was applied to her head, and the other to support it: in
about half an hour these ceased, and the reverie began suddenly, and was at
first manifest by the look of her eyes and countenance, which seemed to
express attention. Then she conversed aloud with imaginary persons with her
eyes open, and could not for about an hour be brought to a