The understanding of how acupuncture works has evolved with its practice, but the descriptions set down a thousand years ago have largely been retained. The dominant function of acupuncture is to regulate the circulation of qi (vital energy) and blood. Approximately 2,000 years ago, the pre-eminent acupuncture text, Huangdi Neijing (Yellow Emperor’s Classic on Internal Medicine), was written. In it, acupuncture was described as a means of letting out excess qi or blood by making holes in the body along certain pathways, called jingluo (meridians). For some of these meridians, it was advised to acupuncture in such a way as to let out the blood but not the qi; for others, to let out the qi, but not the blood. Many diseases were thought to enter the body through the skin, and then penetrate inward through muscle, internal organs, and, if not cured in timely fashion, to the marrow of the bone. By inserting a needle to the appropriate depth-to correspond with the degree of disease penetration-the disease could be let out.
Instead of discussing acupuncture in terms of letting something out of the body, physicians began describing it in terms of regulating something within the body. The flow of qi through the meridians, just like the flow of water through a stream, could be blocked off by an obstruction-a dam across the waterway. In the streams, this might be a fallen tree or a mud slide; in humans, it might be caused by something striking the body, the influence of bad weather, or ingestion of improper foods. When a stream is blocked, it floods above the blockage, and below the blockage it dries up. If one goes to the point of blockage and clears it away, then the stream can resume its natural course. In a like manner, if the qi in the meridian becomes blocked, the condition of the body becomes disordered like the flooding and dryness; if one could remove the blockage from the flow of qi within a meridian, the natural flow could be restored.
In a blocked stream, just cutting a small hole or crevice in the blockage will often clear the entire stream path, because the force of the water that penetrates the hole will widen it continuously until the normal course is restored. In the human body, inserting a small needle into the blocked meridian will have a similar effect. Just as a stream may have certain points more easily accessed (or more easily blocked), the meridians have certain points which, if treated by needling, will have a significant impact on the flow pattern. Many acupuncture points are named for geological structures: mountains, streams, ponds, and oceans.
Although this description of the basic acupuncture concept is somewhat simplified, it conveys the approach that is taught today to students of traditional acupuncture: locate the areas of disturbance, isolate the main blockage points, and clear the blockage. Ultimately, all the descriptions of acupuncture that are based on the traditional model involve rectifying a disturbance in the flow of qi. If the qi circulation is corrected, the body can eliminate most symptoms and eventually-with proper diet, exercise, and other habits-overcome virtually all disease.