[8]. In the section on sleep, it was observed that the nerves of sense are equally alive and susceptible to irritation in that state, as when we are awake; but that they are secluded from stimulating objects, or rendered unfit to receive them: but in complete reverie the reverse happens, the immediate organs of sense are exposed to their usual stimuli; but are either not excited into action at all, or not into so great action, as to produce attention or sensation.
The total forgetfulness of what passes in reveries; and the surprise on recovering from them, are explained in Section [XVIII. 19]. and in Section [XVII. 3. 7].
[9]. It appears from hence, that reverie is a disease of the epileptic or cataleptic kind, since the paroxysms of this young lady always began and frequently terminated with convulsions; and though in its greatest degree it has been called somnambulation, or sleep-walking, it is totally different from sleep; because the essential character of sleep consists in the total suspension of volition, which in reverie is not affected; and the essential character of reverie consists not in the absence of those irritative motions of our senses, which are occasioned by the stimulus of external objects, but in their never being productive of sensation. So that during a fit of reverie that strange event happens to the whole system of nerves, which occurs only to some particular branches of them in those, who are a second time exposed to the action of contagious matter. If the matter of the small-pox be inserted into the arm of one, who has previously had that disease, it will stimulate the wound, but the general sensation or inflammation of the system does not follow, which constitutes the disease. See Sect. [XII. 3. 6]. [XXXIII. 2. 8].
[10]. The following is the definition or character of complete reverie. 1. The irritative motions occasioned by internal stimuli continue, those from the stimuli of external objects are either not produced at all, or are never succeeded by sensation or attention, unless they are at the same time excited by volition. 2. The sensitive motions continue, and are kept consistent by the power of volition. 3. The voluntary motions continue undisturbed. 4. The associate motions continue undisturbed.
Two other cases of reverie are related in Section [XXXIV. 3]. which further evince, that reverie is an effort of the mind to relieve some painful sensation, and is hence allied to convulsion, and to insanity. Another case is related in Class III. 1. 2. 2.
SECT. [XX].
OF VERTIGO.
[1]. We determine our perpendicularity by the apparent motions of objects. A person hood-winked cannot walk in a straight line. Dizziness in looking from a tower, in a room stained with uniform lozenges, on riding over snow. [2]. Dizziness from moving objects. A whirling-wheel. Fluctuations of a river. Experiment with a child. [3]. Dizziness from our own motions and those of other objects. [4]. Riding over a broad stream. Sea-sickness. [5]. Of turning round on one foot. Dervises in Turkey. Attention of the mind prevents slight sea-sickness. After a voyage ideas of vibratory motions are still perceived on shore. [6]. Ideas continue some time after they are excited. Circumstances of turning on one foot, standing on a tower, and walking in the dark, explained. [7]. Irritative ideas of apparent motions. Irritative ideas of sounds. Battèment of the sound of bells and organ-pipes. Vertiginous noise in the head. Irritative motions of the stomach, intestines, and glands. [8]. Symptoms that accompany vertigo. Why vomiting comes on in strokes of the palsy. By the motion of a ship. By injuries on the head. Why motion makes sick people vomit. [9]. Why drunken people are vertiginous. Why a stone in the ureter, or bile-duct, produces vomiting. [10]. Why after a voyage ideas of vibratory motions are perceived on shore. [11]. Kinds of vertigo and their cure. [12]. Definition of vertigo.
[1]. In learning to walk we judge of the distances of the objects, which we approach, by the eye; and by observing their perpendicularity determine our own. This circumstance not having been attended to by the writers on vision, the disease called vertigo or dizziness has been little understood.