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.

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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.  Battement 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.

When any person loses the power of muscular action, whether he is erect or in a sitting posture, he sinks down upon the ground; as is seen in fainting fits, and other instances of great debility.  Hence it follows, that some exertion of muscular power is necessary to preserve our perpendicular attitude.  This is performed by proportionally exerting the antagonist muscles of the trunk, neck, and limbs; and if at any time in our locomotions we find ourselves inclining to one side, we either restore our equilibrium by the efforts of the muscles on the other side, or by moving one of our feet extend the base, which we rest upon, to the new center of gravity.