Weir Mitchell has written fascinatingly of disorders of sleep, making absorbing reading for the profession as well as the laity. He it was who described first the sensory shocks, strange feelings passing along the body, culminating in some abrupt explosion, noise, odor or vision. Vertigo is occasionally thus experienced, especially by those who have felt it before. That mysterious malady called 'migraine' sometimes occurs suddenly while asleep 'and hales the sufferer from profound sleep to waking hours of misery.'
Morbid or perverted sensations, numbness, 'pins and needles' formications and such like mild neuroses appear at times during sleep. Limbs may seem 'dead,' sensation being temporarily lost and not in any way which follows upon marked pressure interrupting the flow of nervous impulses, but purely a phenomenon of sleep. These are more common in the later hours of night, when the motor cells are restored in part, losing irritability, the sensory cells being still excitable. These discomforts may be referred to interruptions in the conductivity of the spinal cord. Nocturnal psychoses, the night terrors of children, nightmare, strange mental vagaries, changes in intellectual and emotional balance, are of such wide variety that they can only be alluded to; each person of rich experience is able to recall instances. In these conditions of distress much folly can be committed, and frequently is; evil thoughts are thus engendered, which too often influence action later. Sometimes imperative impulses arising in slumber drive one to commit questionable or silly deeds. The imagination in some is thus stimulated to utter weird statements, or to put on record what are falsely estimated to be thoughts of deep significance. I recall reading an incident in the early official life of Bismarck, who often thus wakened in the night with the conviction that he had solved perplexing problems. On reducing to writing the ideas thus excited he found, on perusal next day, that they were altogether fanciful. It is true, valuable ideas do come in dreams or in real temporary waking states.
The sleep of early life is peculiarly sensitive to irritations of the organs below the diaphragm, digestive or genital; in later life to those above, of the heart, blood vessels or lungs. In this connection we may refer to dreams. The suspension of brain activity in sleep is only partial; there prevails a certain amount of psychic life. Every nervous stimulus, sensation or idea leaves an impression, a trace, in the cerebro-spinal system. Obscure motions, influences, irritants generated in the organism, may afterward revive temporarily under some impulsation of consciousness, as by afflux of blood. Each cell of the body is endowed with more or less memory (Henle), for by this means are preserved hereditary influences, the transmission of psychic and mental characteristics, the after images of sensations. In this manner many sounds, sights, feelings, which are partially conveyed to the sensorium,
