ANESTHESIA (a, privative, and aistliesis, sensation) is a term used to express a loss of sensibility to external impressions, which may involve a part or the whole surface of the body. In some diseased conditions of the nervous centers, a part of the body may become totally insensible to pain, while, in another part, sensation may be unnaturally acute, or be in a state of hypenesthesia. When a nerve is divided, there is no feeling of touch or pain referred to the parts which it supplies, because these are cut off from communicaVon with the brain; and in some diseases, as the elephantiasis gracerum, a loss of sensation in patches of the skin is an early and characteristic symptom. This insensibility to external impressions may be either peripheral—that is, on the surface of the body—or central, that is, from a cause acting primarily upon the brain or spinal cord.
In ancient writers, we read of insensibility or indifference to pain being obtained by means of Indian hemp (canabis Indica), either inhaled or taken into the stomach. The Chinese, more than 1500 years ago, used a preparation of hemp, or ma-ye, to annul pain. The Greeks and Romans used mandragora for a similar purpose (poiein anaisthesian): and as late as the 13th c., the vapor from a sponge filled with mandragora, opium, and other sedatives was used. The mandragora, however, occasionally induced convulsions, with other alarming symptoms; and though Bul]eyn, an English author (1579), mentions the possibility of putting patients who were to be cut for the stone into "a trance or a deepe terrible dreame" by its use, it gradually became obsolete and banished from the pharmacopoeia. John Baptista Porta, of Naples, in his work on natural magic (1597), speaks of a quintessence extracted from medicines by somniferous menstrua. This was kept in leaden vessels, perfectly closed, lest the aura should escape, for the medicine would vanish away. " When it is used, the cover being removed, it is. applied to the nostrils of the sleeper, who draws in the most subtile power of the vapor by smelling, and so blocks up the fortress of the senses, that he is plunged into the most profound sleep, and cannot be roused without the greatest effort These things are plain to the skillful physician, lint unintelligible to the Wicked." In 1784, Dr. Moore, of London, used compression on the nerves of a limb requiring amputation, but this method was in itself productive of much pain. In 1800, Sir Humphry Davy, experimenting with the nitrous oxide or laughing-gas, suggested its usefulness as an anesthetic; and in 1828, Dr.
Hickman suggested carbonic acid gas. As early as 1795, Dr. Pearson had used the vapor of sulphuric ether for the relief of spasmodic affections of the respiration. The fact that sulphuric ether could produce insensibility was shown by the American physicians Godwin (1822), Mitchell (1832), Jackson (1833), Wood and Bache (1834); but it was first used to prevent the pain of an operation in. 1846, by Dr. Morton, a dentist of Boston. The news of his success reached England on 17th Dee., 1846; on the 19th, Mr. Rob inson, a dentist, and Mr. Liston, the eminent surgeon, operated on patients rendered insensible by the inhalation of sulphuric ether. This material was extensively used for a year, when Sir J. Y. Simpson, of Edinburgh, .discovered the anaesthetic powers of chloroform (see CimonoFoam), and introduced the use of it into his own department, midwifery. Since that time, chloroform has been the antesthetic iu general use in Europe, but either is preferred in America. It is now the opinion of most medical men, that chloroform should not be given where there is weak action of the heart from disease. Other substances have been used by inhalation, such as nitric ether and bichloride of methylene. The latter substance has been recommended by Dr. Richardson, of London; but it has not been generally accepted, as it depresses to a dangerous extent after it has been administered for some time.
Nothing could be more desirable than the power of producing local A. Freezing mixtures have been employed; a stream of carbonic acid or cooled air, or a finely divided spray of ether, have been thrown on the part. All of these methods have the disadvan tage that they injure the tissues, and may be followed by much pain. An agent which would benumb the sensory nerves, without injuring them or the neighboring parts, is still a great want. Recently, in dentistry, the inhalation of nitrous oxide has been much employed. It is rapid in action, and is not usually followed by unpleasant effects; but as it induces a condition in the blood similar to that in asphyxia, its use is not unattended with danger. Chloroform continues to occupy its high place as one of the greatest bless ings granted to man. It is proper, however, to say that it requires to be used under cer tain precautions, and that in unskillful hands its application may be fatal.
See On Chloroform and other Anceetheties, by John Snow (Load., 1858); The Obstetric Memoirs and Contributions of James Y. Simpson (Edin., 1855).