1. Six Meridians Differentiation

1. Six Meridians Differentiation

This approach divides exogenous febrile diseases into six stages according to their path of transmission: Taiyang, Yangming, Shaoyang, Taiyin, Shaoyin, and Jueyin. All formulas are derived from the "Treatise on Cold Damage."

(1) Taiyang Syndrome

Headache, fever, chills, and a floating pulse constitute the basic symptom complex of Taiyang syndrome. If accompanied by anhidrosis and a tight pulse, it is classified as Shanghan (narrowly defined Shanghan), with Mahuang Tang as the representative formula; if accompanied by sweating and a slow pulse, it is classified as Zhongfeng, with Guizhi Tang as the representative formula; if accompanied by thirst, it is considered a warm disease, for which no formula was prescribed in the "Treatise on Cold Damage." From the perspective of the Eight Principles, the Taiyang syndrome can be categorized as either wind-cold exterior excess or wind-cold exterior deficiency. The former corresponds to the exterior heat syndrome, while the latter corresponds to the exterior deficiency syndrome. The treatment methods and formulas for the first two types were clearly outlined in the "Treatise on Cold Damage," whereas the treatment method and formula for the third type—warm disease—were later proposed by the warm disease school, with representative formulas such as Sangju Yin and Yinqiao San (both from the "Differentiation of Warm Diseases").

(2) Yangming Syndrome

High fever, intense thirst, profuse sweating, and a large, forceful pulse characterize the Yangming meridian syndrome; fullness, distension, dryness, and solid accumulation define the Yangming fu syndrome. The representative formula for the meridian syndrome is Baihu Tang, while the representative formula for the fu syndrome is Chengqi Tang (including Dachengqi Tang, Xiaochengqi Tang, and Tiaowei Chengqi Tang).

From the perspective of the Eight Principles, the Yangming syndrome falls under the category of interior excess heat. When the heat is more concentrated in the meridians, it is classified as the Yangming meridian syndrome; when the heat is more concentrated in the fu organs, it is classified as the Yangming fu syndrome. The meridian syndrome indicates that the heat is dispersed throughout the meridians, while the fu syndrome indicates that the heat is concentrated in the fu organs. The former is intangible, while the latter is tangible. "Pi" refers to epigastric fullness and discomfort, "man" refers to abdominal distension, "zao" refers to dry stools, and "shi" refers to abdominal pain due to internal obstruction.

(3) Shaoyang Syndrome

Bitter taste in the mouth, dry throat, dizziness, alternating chills and fever, chest and flank fullness and discomfort, irritability and nausea, reluctance to drink, and the use of Xiao Chaihu Tang; if accompanied by headache, chills, and fever, it is classified as the Shaosha combined syndrome, treated with Chaihu Guizhi Tang; if accompanied by constipation and thick yellow tongue coating, it is classified as the Shaoyang-Yangming combined syndrome, treated with Da Chaihu Tang.

From the perspective of the Eight Principles, the Shaoyang syndrome is a semi-exterior, semi-interior syndrome. As long as one of the seven symptoms of Shaoyang is present, a diagnosis of Shaoyang syndrome can be made. This syndrome is relatively common, and many systemic reactive syndromes associated with subacute and chronic inflammation in modern medicine fall into this category.

(4) Taiyin Syndrome

Abdominal fullness and vomiting, inability to eat, worsening of symptoms after eating, intermittent abdominal pain—these are the main symptoms of Taiyin syndrome, treated with Lizhong Tang. From the perspective of the Eight Principles, this syndrome is classified as spleen-stomach deficiency-cold syndrome.

(5) Shaoyin Syndrome

The hallmark of Shaoyin syndrome is a weak, fine pulse and a strong desire to sleep, treated with Sini Tang. From the perspective of the Eight Principles, this syndrome is classified as heart-kidney yang deficiency syndrome, with yang deficiency progressing to yang collapse, indicating a severe case of yang deficiency requiring urgent resuscitation. Sini Tang is the appropriate formula for such cases. From a modern medical perspective, this syndrome represents peripheral circulatory failure.

(6) Jueyin Syndrome

Thirst, upward rushing qi to the heart, burning sensation in the heart, hunger without appetite, vomiting of worms after eating—these are the main symptoms of Jueyin syndrome, treated with Wumei Wan.

The clinical manifestations of Jueyin syndrome are quite complex, and there has been inconsistent understanding among physicians throughout history. The above-mentioned symptom complex is only one set of symptoms among many that can represent Jueyin syndrome, and people often regard this set of symptoms as the typical manifestation of Jueyin syndrome. From the perspective of the Eight Principles, this syndrome is classified as a mixed cold-heat syndrome; from a modern medical perspective, it is classified as intestinal ascariasis or biliary ascariasis.

The Six Meridians differentiation is the essence of the "Treatise on Cold Damage." It describes the six different stages at which exogenous cold pathogens invade the body: starting with Taiyang, then progressing to Yangming; it is also possible to bypass Taiyang and directly attack Yangming. Alternatively, one can move from Yangming back to Taiyang, or from Shaoyang to Taiyin, Shaoyin, or Jueyin. The "Treatise on Cold Damage and Miscellaneous Diseases" was compiled at the end of the Eastern Han Dynasty, but during the wars its original text was scattered and lost. Although Wang Shuhe later reorganized it, the complete original form remains unverifiable. Throughout history, physicians such as Fang Youzhi and Yu Jiayan have expressed regret over this, with Yu Jiayan using the metaphor of "cutting up beautiful brocade and patching it with scraps of old cloth" ("Shanglun Pian") to describe the imperfections in the work. Contemporary physician Yan Derun stated: "In fact, the Three Yin Meridians are not truly transmitted" ("Commentary on the Treatise on Cold Damage"). Lu Yuanlei believed: "Since we classify whole-body deficiency-cold as Shaoyin, gastrointestinal deficiency-cold as Taiyin, and there is no other type of deficiency-cold that could reasonably be classified as Jueyin, we are essentially forced to make arbitrary distinctions, which is an overextension of the number of meridians and a case of forcing the shoe to fit the foot" ("Modern Interpretation of the Treatise on Cold Damage"). The criticisms raised by these physicians regarding the Six Meridians differentiation demonstrate the need for further refinement and development of this diagnostic method. However, the formulas and symptom patterns revealed by the Six Meridians have stood the test of time and remain a timeless treasure, a point on which all physicians throughout history have agreed.