PARALYSIS, the loss of the natural power of sensation or motion in any part of the body. It is owing to some. dis eased condition of the nervous system, either of the brain or spinal cord, or of the nerves. If the nerves of sensation or their centers be affected, there will be loss of sensation; if of motion, then loss of motion; to the latter of which the term paralysis is by some exclusively ap plied. The most usual form is when one side or half of the body is deprived of sensation or motion, or both, called hemiplegia; paraplegia is when the lower part of the body is paralyzed, while the upper retains both sensation and motion; and general paralysis is when the loss of nervous power extends over nearly every part of the body. In hemiplegia, the seat of the disease is one side of the brain, usually that op posite to the affected side of the body; in paraplegia, the lesion is within the spinal cord; and when more limited in extent, the disease usually arises from some abnormal state of a particular nerve. Paralysis frequently follows apoplectic attacks, and this usually in its most severe and dangerous form. The prognosis must be looked on as extremely unfavorable when the attack is sudden, the paralysis extensive and complete, and the loss of consciousness protracted; while, on the other hand, when the pa ralysis advances gradually, there is more reason to hope for prolonged life, if not for a complete restoration of health.
Among the other causes that may give rise to paralysis are various injuries and diseases of the brain or spinal cord; as tumors, inflammation, external injuries, etc. When paralysis takes place with out any previous apoplectic attack, the premonitory symptoms are a general torpor or lassitude, occasional giddiness, or a sense of weight and pain in the head, and loss of memory. When it is the result of injury of the spinal cord, then, of course, the paralysis takes place instantly. Paraplegia sometimes lasts for many years without greatly interfer ing with any function except locomotion; but when it occurs during fevers and ad vances rapidly, it is of very sinister au gury, especially if it involves the sphinc ter muscles of the anus and bladder. Paralysis is not a disease of itself, but only a sign of some disorder of the ner vous system, probably at a distance from parts affected.