The condition of the great nervous centers during sleep is a subject of much interest, on which considerable light has recently been thrown by the observations of Mr. Durham.* „These observations were made on a from which a portion of bone about as large as a shilling was removed from the parietal region of the skull, and the subjacent dura mater cut away so as to expose the brain; and Mr. Durham draws the following conclu sions from them: 1. Pressure of distended veins upon the brain is not, as is generally believed, the cause of sleep, for during sleep the veins are not distended. 2. During sleep, the brain is in a comparatively bloodless condition; and the blood,in the encephalic vessels is not only diminished in quantity, but mores with diminished rapidity; and this is corroborated by the observations of Dr. J. Hughlings Jackson on the ophthalmoscopic condition of the retina during sleep, the optic disk being then whiter, the arteries smaller, and the retina generally more anemic than in the waking state. 3. The condition of the cerebral circulation during sleep is, from physical causes, that which is most favorable to the nutrition of the brain-tissue.
This article would be imperfect without a brief reference to the conditions in which there is either an excess or a deficiency of sleep. There arc numerous instances on record in which sleep has been continuously prolonged for weeks, or even months. Dr. Carpenter refers to two such cases, namely, those of Samuel Chilton (Plot. Trans. 1694) and Mary Lyall (Trans. Roy. hoc. Edin. 1818). Blanchet, a French physician, has recently recorded three eases of what he terms "constitutional lethargic slumber" in the Comptes Rendus, 1864. In one of these cases, the patient, a lady aged 24 years, who had slept for 40 days when she was 18 years of age, and 50 days when she was 20, at length had a sleep of nearly a year, viz., from Easter Sunday, 1862, to March, 1863. During this period, a false front tooth was removed in order to feed her with milk and soup, her only coed. She was motionless and insensible. The pulse was low, the breathing scarcely perceptible, there were no evacuations, and she showed no signs of leanness, her complexion remaining florid and healthy. In such cases as these, it is not a pro long.arion of healthy natural sleep that is present, but a condition of hysteric coma.
Again. there are curtail' states of the nervous system in which there is either an entire ahsenee of sleep (and this may continue for many days, or even weeks) or incomplete sleeplessness. Complete sleeplessness is often a most important symptom Of disease. It
frequently accompanies certain forms of continued fever, inflammatory affections of the brain, the eruptive fevers, etc., and when it continues for many days and eights, delirium. followed by stupor, is very apt to supervene. When the wakefulness is unattended by any disorder sufficient to account fur it, some serious disease of the brain is most probably impending, such as palsy, apoplexy, or insanity. Incomplete or partial sleeplessness is a symptom of far less grave import. It is of frequent occurrence in persons whose minds are much engaged, or whose occupations subject them to great mental exertion or to the vicissitudes of fortune. It is, moreover, a symptom of many chronic diseases, as gout, chronic rheumatism, skin-diseases, disorders of the urinary organs, dyspepsia., hysterica, etc. It may also be excited by certain beverages and articles of diet; thus green tea and strong caffee often occasion wakefulness, and a full meal of animal food late in the day often disturbs the sleep of persons accustomed to dine at an earlier hour.
In the treatment of sleeplessness, or insomnia, as it is usually termed by medical writers, the first indication is to remove the cause, which occasions it, and " more par ticularly to correct a close or contaminated air; to reduce the temperature of the apart ment when it is high, arid the quantity and warmth of the bedclothes: to remove all thel excitants to the senses; to abstract the mind from all exciting, harassing, or engaging thoughts; and to remove or counteract the morbid conditions 01 which this is a symptom or prominent consequence."—Copland's Dictionary of Medicine, art. " Sleep and Sleep lessness." A careful regulation of the secretions, by the due use of purgatives and alteratives, will often remove this symptom; and rec airsc should not be had to anodynes and narcotics until morbid secretions and fecal accumulations have been completely got rid of. But these medicines are of great service when the system is thus prepared for their reception. The choice of the individual drug or combination of drugs must be dependent upon the peculiarities of the case, but, as it general rule, there is no more serviceable narcotic mixture for an adult than 25 or 30 minims of the solution of hydro chlorate of morphia (of tire British Pharmacopceia), and 10 minima of chloric ether, taken in half a wine-glassful of water: medicines of this class should, however, never be resorted to without the advice of a physician.