of the blood vessels and thus the vasomotor mechanisms are taxed heavily. The head should be permitted to rest as nearly upon a level as the feet, though most people prefer some support. The blood should be encouraged to reach all parts of the body equally, hence the limbs had best be extended, not flexed; the habit of extending the arms above the head is a particularly bad one.
To secure the most perfect repose the temperature of all parts should be equalized before retiring. Cold feet induce delay in securing sleep and it is then shallow when attained. The bladder and bowels by weight of their contents will interfere with repose, hence they should be previously emptied. It is most unwise to overfill the stomach before retiring; this disturbs sleep almost as much as hunger, but moderate eating before sleeping is not hurtful, and is often salutary.
Sleep is only a function; therefore, whatever disturbs it depends on structural derangement of some sort. Disorders of sleep are manifold. The commonest are psychic exaltations or depressions, worries, brooding on the cares of the day, continuing to dwell on the waking problems. Habit is ever forceful. A well-trained mind will promptly shut off or readily let go of the thought processes. Unnatural activity of the sensory and association centers causes dreams; that of the motor centers results in shocks, starts and spasmodic phenomena. Control of the visceral centers may become inhibited, permitting unconscious discharges from the bladder, intestines or sexual organs; innervation of the lungs or heart being thus deranged, palpitation or dyspnoea is induced. Sensory centers being over-stimulated, sensations of light follow, or of sound, also pain or vertigo. "In fine, the ordinary smooth current of the subconscious activities breaks against some pathologic states and now one symptom, now another, is thrust out and so unpleasantly that the sleeper awakens" (C. L. Dana).
A review of Dana's remarks on the disorders of sleep will be useful to achieve an understanding of the varieties and phenomena of insomnia; a better term perhaps would be difficulties of sleep. Some people, especially those of middle age, fall asleep easily, but wake in the small hours and thereafter only doze fitfully. This may be due to beginning degenerative changes in the arteries, connected with the effects of worries and strains, or only a habit, or echo of youthful customs of early rising, or an acquired weakness or irritability of the heart. Others fall asleep readily, but are soon disturbed by little explosions of motor, sensory or psychic forces. The body or limbs start or jerk; sleep follows, but these nervous explosions may be repeated two or three times. It is usually the result of exhaustion, psychic or muscular over-tension, physiologic irritability, indigestion, nervous fatigue, or may foreshadow some serious derangement. Sudden awakenings often betray emotional distress, fear or disorders of ideation.
