1) Directing the Diagnosis of Diseases
Because meridians and collaterals have fixed courses of extension in the body, and a fixed connection with the viscera, the symptoms and signs of viscera disease are easily manifested. In clinical practice, the meridian system can be the foundation of diagnosis according to the positions of symptoms, and used in combination with the meridian distributions and their related viscera. For example, pain in both hypochondriac regions is mainly due to liver and gallbladder diseases; while pain in the supraclavicular fossa is usua11y caused by lung diseases. Headaches are another example. The pain in the forehead is related to the Yangming Meridian, pain in both lateral sides with Shaoyang Meridian, Dain in the occipital region and nape with Taiyang Meridan'pare in vertex with Jueyn Meridian.

The diagnosis of the six meridian syndromes in the Treatise on Cold Attacks is accompllished through use of the syndrome differentiation system developed from meridians theory. In addition, it is helpful to diagnose pressure pare,and the tubercular or rectangular reactive substances in places the meridians pass or where the meridian-qi gathers at some acupoints. It is helpful as well to diagnose morphological changes in the local areas of skin.

An example of this diagnosis is the disorder of the lung-viscus. When it is not functioning properly, tubes in the Feishu acupoint area, and pressure pare in the Zhongfu acupoint area can occur. Another example is that pressure pain in the Lanwei extra-point will appear in patients with appendicitis. Abnormal changes in Pishu acupoint usually appear in chronic indigestion. Just as Chapter 73 in the Spirit Pivot says:"The pain can be diagnosed by observing the left parts, the right parts, the upper parts and lower parts of the body, as well as its nature of cold or warm. Then the meridian it attaches to can be decided." This reiterates that the meridians are of great significance in clinical diagnosis.

2) Guiding the Treatment
The meridian theory is broadly applied in clinical treatment, and IS of great guiding significance, especially regarding the therapies of acupuncture,moxibustion, massage and Chinese herbs.

The therapy of acupuncture and massage use points from local spots near the affected area, or use distant points along the meridians length in order to regulate the functional activities of q i and blood of the meridians, thus good therapeutic effect is achieved. However, the point-taking must be determined through the guidelines of the meridian theory. Through these guidelines one can differentiate and decide which meridian the disease is treatable form and then choose the points based on the distributions and communicating ranges of the meridians. This is called "taking the points according to the meridians."

Herbal therapy also relies on the meridian theory. The herbs take effect through the channelling function of the meridians, which deliver the herbs to the affected part. Based on long-term clinical practice, ancient doctors formed a new theory called "meridian tropism of herbs." This involved the specific selectivity of herbs geared toward one of the meridians.