The basic functions of the meridians and collaterals

• This channel starts from the tip of the radial side of the index (Point Shangyang, LI 1). It runs upwards along the radial side of the index and passes between the ossa metacarpalia I and 1 I, goes into the depression between the tendons of m. extensor pollicis longus and brevis, then along the antero-lateral aspect of the forearm to the lateral side of the elbow (Point Quchi, LIll). Along the anterior border of the lateral side of the upper arm, it ascends to the highest point of the shoulder (Point Jianyu, LI 15), and then goes along the anterior border of the acromion up to 7 th cervical vertebra (Point Dazhui, DU 14), from where it comes downwards into the supraclavicular fossa and communicates with the lung. Descending through the diaphragm, it enters its pertaining organ, the large intestine. The branch channel from the supraclavicular fossa runs upwards to the neck, passes through the cheek, and enters into the lower teeth and gum. Then it curves round the lips and meets at Point Renzhong(DU 26), or philtrum, thevertical groove on the mid-line of the upper lip. From there the channel ofthe left side turns right, while the right side channel turns left. They go upwards to both sides of the wings of the nose (Point Yingxiang, LI 20) and connect with the Stomach Channel of Foot-Yangming.

The basic functions of the meridians and collaterals • There are two basic functions of the meridians and collaterals. One is to connect the external with the internal as well as to connect the viscera with other organs. The other is to transport qi, blood, yin and yang to nourish the viscera and the body. In physiology, pathology and treatment, the meridians and the collaterals are responsible for the transmission and conduction of physiological and pathological information as well as the regulation of the physiological functions of the body.

To connect the external with the internal as well as to connect the viscera with other organs • The body is an organic whole. It is the meridians and collaterals that connect the viscera, the body, the five sensory organs and the nine orifices together. The meridians internally pertain to the viscera and externally connect the limbs. Since the meridians are composed of various collaterals of different levels, they have formulated the whole body into a network. There are three basic ways with which the meridians to connect all parts of the body together.

The relationships between the viscera, the body, the sensory organs and the orifices • The connection between the external and the internal as well as the viscera and other organs is mainly accomplished by the twelve meridians. On the one hand the twelve meridians and their branches accomplish such a connection by emerging from the external of the body and entering the internal of the body. On the other hand, they reinforce such a connection with the twelve branches, twelve tendons and twelve skin divisions.

The relationships between the zang-organs and fu-organs • The twelve meridians has formed six pairs of external and internal relationships which enable the zang-organs and the fu-organs in external and internal relationships to connect with each other. The meridians stemming from the viscera associate with several internal organs during their running processes. As a result each zangorgan or fu-organ is connected with several meridians.

The relationships among the meridians • The twelve meridians are connected with each other, follow a certain running and infusing order and together form a large circulatory system. The twelve meridians and the eight extraordinary vessels have formulated a crisscross network. The extensive association among the meridians and collaterals enables the body to become an organic whole.

To transport qi, blood, yin and yang to nourish the viscera and the body • All the viscera and other parts of the body depend on qi, blood, yin and yang to nourish and maintain their physiological functions. It is the meridians that transport qi, blood, yin and yang to the whole body. In fact, the meridians and collaterals are the passages of qi, blood, yin and yang. The purpose of the meridians to connect the viscera and the body is to transport qi, blood, yin and yang. With the extensive distribution of the meridians and collaterals, qi, blood, yin and yang in the body can flow freely to maintain a holistic balance of the body.

The functional characteristics of the eight extraordinary vessels • Apart from sharing the same functions with the twelve meridians, the eight extraordinary vessels still have three special functions. The first is to strengthen the connection of the twelve meridians. For example, the governor vessel accumulates qi and blood in all the yang meridians; the conception vessel accumulates qi and blood in all the yin meridians; the thoroughfare vessel accumulates qi and blood in the twelve meridians; the yang-link vessel connects all the yang meridians together; and the yin-link vessel connects all the yin meridians together. The second is to regulate qi and blood in the twelve meridians. When qi and blood in the twelve meridians are excessive, they then flow into the eight extraordinary vessels to store up. If qi and blood in the twelve meridians are insufficient, the eight extraordinary vessels will infuse some qi and blood stored in them into the twelve meridians. The third is to govern some of the special physiological activities of women. Since thoroughfare, conception and governor vessels all start from the uterus, they are closely related to the menstruation, pregnancy and labor of women. Since the belt vessel runs transversely around the lower abdomen, it can protect fetus and controls leukorrhea.

The clinical application of theory of meridians and collaterals • The occurrence of exogenous disease is usually caused by invasion of pathogenic factors which first attack the surface of the body, then invade the collaterals with scanty defensive qi, and gradually get into the internal part of the body.

To explain pathogenesis and pathological transmission

To explain the pathogenesis • The occurrence of exogenous disease is usually caused by invasion of pathogenic factors which first attack the surface of the body, then invade the collaterals with scanty defensive qi, and gradually get into the internal part of the body. The occurrence of endogenous disease is caused either by insufficiency or imbalance of qi, blood, yin and yang. If qi, blood, yin and yang are insufficient, the meridians and collaterals will become empty; if qi, blood, yin and yang have lost balance, the meridian qi will be stagnated or in disorder, leading to the occurrence of disease.

To explain pathological transmission • Disease is usually transmitted along the meridians. The exogenous pathogenic factors are transmitted from the external to the internal, from the collaterals to the meridians, and from the meridians to the viscera. Thus the pathological changes of the viscera can be transmitted by the meridians. For example, disease of the zang-organs can be transmitted to the fu-organs and the disease of fu-organs can be transmitted to the zangorgans by the meridians in external and internal relationship with each other. On the other hand, the diseases of the five zang- organs can be transmitted among them because of the multiple relationships among the meridians and collaterals

• For example, the liver disease can be transmitted to the lung and the stomach; the kidney disease can be transmitted to the heart and the lung; etc. Besides, disease of the internal organs can be transmitted to the surface of the body, leading to pathological changes of the related constituents, organs and orifices. For example, angina pectoris may lead to tenderness on medial side of the upper limb along which the heart meridian runs; the disease caused by stomach-fire may cause swelling pain of the gums through which the stomach meridian runs; up-flaming of liver-fire may cause ocular disease, etc.

To guide the diagnosis and treatment of disease

To guide the diagnosis of disease • Since the meridians run along certain routes and pertain to certain viscera, there is a special relationship between different parts of the body and the internal organs. Clinically the relationship between the pathological location or the disease and the meridians can be used to decide which meridian and viscus are involved so as to make an accurate diagnosis.

• For example, the liver meridian distributes over the hypochondrium, so hypochondriac pain indicates liver disease; the lung meridian emerges from the supraclavicular fossa, pain in the supraclavicular fossa indicates lung disease. Take headache for another example. It usually appears in different regions. Pain in the forehead is related to the yangming meridian; pain in both sides of the head is usually related to the shaoyang meridian; and pain in the nape is often related to the taiyang meridian. Besides, some diseases show special reaction points on certain acupoints. If tenderness appears on these reaction points, it is very helpful for diagnosis. For example, intestinal abscess will lead to tenderness on Lanwei (EX-LE 7), gallbladder disease will bring on tenderness on Yanglingquan (GB 34).

To guide the treatment of disease • The theory of the meridians and collaterals is extensively used in clinical treatment, especially in acupuncture and moxibustion, massage and drug treatment.

• The treatment of disease by acupuncture, moxibustion and massage is usually done by needling or massaging the acupoints proximal or distal to the affected part on the meridians to regulate the functional activities of the meridian qi and blood. To select acupoints, one has to differentiate the syndrome first with theory of the meridians and collaterals to decide which meridian the disease is related to, and then select acupoints in the light of the running route and coverage of the meridian. Such a way to select acupoints is called "selection of acupoints along the meridians".

• Drug treatment also has to be done according to theory of meridians and collaterals because the meridians and collaterals can transport the effect of the drugs to the affected part. In the long course of clinical practice, TCM has developed theory of "meridian tropism of drugs" which holds that each drug can enter one or more meridians. With the guidance of this theory, clinically drugs are selected, based on syndrome differentiation, according to their state of "meridian tropism" to treat disease so as to improve therapeutic effect.

• Again take headache for example. If it is related to the taiyang meridian, Qianghuo (Rhizoma seu Radix Notopterygii) should be used; if it is related to the yangrning meridian, Baizhi (Radix Angelicae Dahuricae) should be used; if it is related to the shaoyang meridian, Chaihu (Radix Bupleuri ) should be used, because these drugs enter to these meridians respectively. In the formulation of a prescription, one or two drugs that enter a certain meridian can be added in order to guide the other drugs, which normally do not enter that meridian, to work on that meridian. The drug that leads other drugs to work on a certain meridian or organ is called "guiding drug".