The meridians and collaterals (finer branches) are pathways that carry Qi, blood, and body fluid around the body. They are the communication lines between all parts of the organism. The Canon of Difficult Medical Problems states: “The meridians move blood and Qi and ensure the free flow of Yin and Yang, so that the body is properly nourished.” The organs, orifices, skin and hair, sinews and flesh, bones, and other tissues all rely on communication through the meridians, forming an integrated, unified organism.
The theory of meridians and collaterals, derived to some extent from human anatomy, is an important element of Chinese medicine. The Canon of Medicine states: Regard the body of an eight cubit man; when alive, take his measurement, feel his pulses; when dead, dissect his body and regard the strength of his viscera, the size of his bowels, the volume of the trunk cavity and the organs within it, the length of the meridians, the clarity of the blood and the state of the Qi. All are shown to conform to a standard.
This quotation provides evidence that by the time of the Warring States Period, knowledge about the meridians was gained from human anatomy. However, the theory of meridians and collaterals was largely derived from clinical practice and the subjective experiences of patients undergoing acupuncture treatment. Thus, this theory represents a synthesis of anatomical and clinical findings with subjective sensory experience. It is applied in the clinical practice of all branches of medicine, particularly in acupuncture and moxibustion, and has led to major medical developments such as acupuncture anesthesia.
The meridians and collaterals include the major trunks and minor branches. The meridian vessels have clearly defined pathways that penetrate deep into the body; the network vessels are their branches. The Gateway to Medicine states: “The meridians represent the main pathways and their ramifications are the collaterals.” There are two types of meridians: the twelve meridians and the eight extraordinary meridians. Concerning the difference between the meridians and the extraordinary collaterals, The Salvation General Compendium states: There are ordinary and extraordinary meridians. The regular meridians are the twelve meridians. The eight extraordinary meridians are so named because they do not conform to the norm. Qi and blood constantly flow through the twelve meridians and, when abundant, overflow into the extraordinary meridians.
The collaterals are described in three categories: the large ones, of which there are fifteen, serve to connect interior (Yin) and exterior (Yang) major meridians. Those that run through the exterior of the body are called superficial collaterals. Their finer ramifications are known as the minute collaterals. Twelve meridians enhance communication between organs and the major meridians and between the meridians themselves. Finally, twelve meridian muscle and twelve cutaneous regions divide the body’s musculature and integument into twelve distinct regions corresponding to the twelve meridians.
The theory of meridians and collaterals is of significance in physiology, pathology, pattern identification, and treatment. In physiology, the meridians represent the principal pathways by which Qi, blood, and body fluid are distributed around the body, providing nourishment and warmth. They also serve as vital links among the organs and other parts of the body. The Canon of Medicine explains: The meridians are the routes by which blood and Qi circulate, regulating Yin and Yang, keeping the bones and sinews moistened and the joints lubricated.
The blood and body fluid are carried through the meridians by Qi and in acupuncture the sensation produced when obtaining Qi shows that the meridian is live, or has abundant Qi. The meridians are the transmission lines between the various parts of the body, making the organism a unified whole.
In pathology, external evils invade the body through the exterior and penetrate into the interior, affecting the organs. The Canon of Medicine states: An evil settling in the body must first abide in the skin and hair. If it resists expulsion, it will enter minute collaterals. If it continues to resist, it will enter the larger collaterals. If it persists, it will enter the major meridians that communicate with the organs in the inner body. When the evil spreads to the stomach and intestines, Yin and Yang are both affected and all the organs suffer damage. This is the sequence by which evils penetrating the body through the surface skin and hair eventually affect the five viscera.
Similarly, organ pathologies may spread to other parts of the body through the meridians. A disorder in a given organ may be transmitted through the relevant meridian, manifesting as morbidity in regions along the meridian’s course. An example of this is seen in liver fire flaming upwards which may be characterized not only by red eyes and pain in the center of the chest, but also by pain in the related meridian along the inner face of the arm. Disease in one organ can also spread to other organs through the meridians. Examples include heart fire, which can spread to the small intestine, and kidney vacuity water-flood which intimidates the heart or shoots into the lung. Through meridian transmission, morbidity in the organs may also be reflected in areas of palpatory tenderness, swellings, indentations, nodes, and hyperemia. These signs are often helpful in diagnosis.
The main significance of meridian theory in pattern identification and treatment is found in a series of methods based on the laws governing the flow of meridian Qi, interorgan connections, physiopathologic characteristics of the meridians, and meridian interrelationships. There are three most common uses of these methods. Determining meridian relevance based on pathology location involves determining the meridians relevant to a disorder based on its location. Pattern identification by meridians involves evaluating symptoms based on the physiopathologic features of the meridians. Selection of acupoints and medicinals according to meridian involves determining treatment through the physiopathologic features of the meridians.
Organs and Meridians
For example, the forehead, cheeks, teeth, lips, and throat are all located on the foot Yang brightness (Yangming) stomach meridian and the hand Yang brightness (Yangming) large intestine meridian. Therefore, disorders such as frontal headache, wind-fire toothache, and sore throat may be treated as Yang brightness (Yangming) meridian disorders. In acumoxatherapy, they are treated by needling the points ST-6 (Jawbone), ST-7 (Below the Joint), ST-36 (Leg Three Li), and ST-44 (Inner Court) on the foot Yang brightness (Yangming) stomach meridian. LI-4 (Union Valley) and LI-1 (Shang Yang) on the hand Yang brightness (Yangming) large intestine meridian also may be chosen. If medication is indicated, agents that dissipate Yang brightness (Yangming) wind-fire, and agents that clear Yang brightness repletion heat may be used. Since the hand and foot Yang brightness meridians are linked to the intestines and stomach, agents that flush gastrointestinal heat-bind also may be used.
To sum up, the theory of meridians and collaterals represents an important part of the body of medical theory, and is widely applied in pattern identification and treatment in the clinical practice of all branches of medicine. It is of greatest importance in organ pattern identification and six-meridian pattern identification; in external medicine, where attention is paid to the proximity of pathologies to meridians; and in the regulation of the penetrating and conception vessels in gynecology. Recent research has led to major advances in acuanesthesia, as well as facial and scalp acupuncture.