I. The Source and Evolution of the Six Meridians Syndrome Differentiation

1. From the “Inner Canon” to the “Treatise on Cold Damage”

• “The Discussion of Heat in the Basic Questions” first proposed the theory of the “three yin and three yang” six meridians, but it was not directly linked to clinical syndrome differentiation.
• Zhang Zhongjing creatively developed the six meridians (Taiyang, Yangming, Shaoyang, Taiyin, Shaoyin, Jueyin) into a dynamic energy layer model in the “Treatise on Cold Damage” for analyzing the transmission patterns of exogenous diseases.

2. Zhu Gong’s Naming Contribution in the Song Dynasty

• Zhu Gong first named the “three yin and three yang diseases” in the “Treatise on Cold Damage” as “six meridians” in the “Classified Book for Saving Lives,” but its essence is a six-layer energy defense system, not merely a concept of meridians.

The “six meridians syndrome differentiation” in the “Treatise on Cold Damage and Miscellaneous Diseases” is not exactly the same concept as the six meridians in the “Inner Canon.”

The “Treatise on Cold Damage” does not mention the name “six meridians.” Throughout the entire “Treatise on Cold Damage,” it discusses the diagnosis and treatment of Taiyang disease, Yangming disease, etc., without mentioning Taiyang meridian or Yangming meridian. The one who named it “six meridians syndrome differentiation” was not Zhang Zhongjing, but Zhu Gong from the Song Dynasty. In his “Classified Book for Saving Lives,” he first referred to the three yin and three yang diseases in the “Treatise on Cold Damage” as the six meridians, and this is the origin of what we later call the six meridians syndrome differentiation. Zhu Gong named it the six meridians because it directly comes from “The Discussion of Heat in the Basic Questions.”

The six meridians in the “Treatise on Cold Damage” originally refer to six different layers of energy, which can also be understood as different defense mechanisms.

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II. The Core Theory of the Six Meridians Energy Layers

(With Energy Layer Diagram)
1. Correspondence Between the Six Meridians and Energy

Six Meridians	Energy Level	Physiological Function	Pathological Manifestation
Taiyang	Surface Defense	Regulating body temperature, resisting external pathogens	Aversion to cold, fever, absence of sweat or spontaneous sweating
Yangming	Internal Supply	Digestion and absorption, generation of qi and blood	High fever, constipation, thirst
Shaoyang	Pivotal Regulation	Regulation of qi movement, balance of yin and yang	Alternating chills and fever, fullness in the chest and hypochondrium
Taiyin	Generation of Qi and Blood	Transportation and transformation by the spleen and stomach, distribution of body fluids	Abdominal distension, loose stools, loss of appetite
Shaoyin	Fundamental Nourishment	Interaction between the heart and kidney, storage of yang qi	Cold limbs, mental fatigue
Jueyin	Dynamic Balance	Dispersion of liver qi, transformation between yin and yang	Cold hands and feet, vomiting of roundworms

2. Dialectical Relationship Between Meridians and Energy Layers

• Taiyang Meridian (Bladder Meridian, Small Intestine Meridian): Governs surface defense; when the meridian qi is abundant, the pores open and close freely (e.g., Gui Zhi Tang activates the yang qi of the Taiyang layer).
• Yangming Meridian (Stomach Meridian, Large Intestine Meridian): Rich in qi and blood, serving as an “energy reinforcement unit” (e.g., sweating through Hegu point requires the qi of the Yangming meridian).
• Taiyin Meridian (Spleen Meridian, Lung Meridian): When the spleen and stomach are deficient, all diseases arise (e.g., children’s cough requires strengthening the spleen rather than just stopping the cough).

How are the Taiyang, Shaoyang, Yangming, Taiyin, Shaoyin, and Jueyin meridians related to different levels of energy? Meridians are the specific manifestations of different levels of energy. But energy is not equivalent to just meridians.

For example: the Hand Taiyang Small Intestine Meridian and the Foot Taiyang Bladder Meridian. Both belong to the energy of the Taiyang layer. They both govern the surface: the surface that contacts the outside world. When the Bladder Meridian’s qi is abundant, the back is less likely to catch a cold. When the Small Intestine Meridian’s qi is abundant, food is easily digested without stagnation.

The Taiyang in the “Treatise on Cold Damage” is different from the Taiyang meridian. The Taiyang layer is the surface energy and is not limited to the skin areas where the Hand and Foot Taiyang meridians run; all skin areas can be attributed to the Taiyang layer. However, activating the qi of the Hand and Foot Taiyang meridians can achieve the effect of opening all the pores of the body.

When treating Taiyang surface symptoms, we use the medical principle of activating the Taiyang meridian’s qi to relieve the exterior, such as drinking a bowl of Cong Chi Tang, Ginger Soup, or Gui Zhi Tang, all of which activate the body’s yang qi. The first to be activated is the Taiyang layer.

Similarly, we can also directly scrape the back, use acupuncture, etc. Speaking of acupuncture, we might not needle the Taiyang meridian but instead needle the Yangming meridian, such as Hegu point for sweating. Why? Because the Yangming meridian is the only one of the twelve regular meridians that is rich in qi and blood. The reason people catch a cold is still due to insufficient Taiyang meridian qi. So, we divert some energy from the Yangming meridian, which is the most abundant in energy, like a reinforcement unit.

And if it progresses to a cough? At this point, you need not only to relieve the exterior but also to clear the lungs and relieve the exterior. The reason it turns into a cough is because there is an internal and external cooperation of the Taiyin. Many children directly cough after catching a cold, which is directly related to lung and spleen deficiency. Some doctors prescribe formulas that only clear the lungs and stop the cough, without paying attention to the spleen and stomach. Therefore, a situation may arise: the child recovers, but the next time they catch a cold, they cough again directly.

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III. Clinical Practice: The Application Logic of Six Meridians Syndrome Differentiation

(With Tongue Image and Medication Guide)
1. Taiyang Surface Syndrome: Relieving the Exterior First

• Tongue Image: Pale red tongue, thin white coating, floating and tight pulse.
• Classic Formulas:
  • Gui Zhi Tang (Harmonizing营卫, activating the Taiyang layer’s yang qi).
  • Cong Chi Tang (Dietary therapy: 3 scallions + 10g of fermented soybeans, sweating to relieve the exterior).
• External Treatment: Scraping the back (along the Bladder Meridian) or moxibustion at the Dazhui point.

2. Yangming Internal Syndrome: Purging the Bowels and Clearing Heat

• Tongue Image: Red tongue with yellow coating, surging and large pulse.
• Classic Formulas:
  • Bai Hu Tang (Gypsum + Anemarrhena to clear heat in the Yangming qi division).
  • Tiao Wei Cheng Qi Tang (Rhubarb + Mirabilite to purge the bowels and clear heat).

3. Shaoyang Pivotal Syndrome: Harmonizing Shaoyang

• Tongue Image: Red tongue with thin yellow coating, wiry and fine pulse.
• Classic Formulas:
  • Xiao Chai Hu Tang (Bupleurum + Scutellaria to harmonize Shaoyang, balancing the liver, gallbladder, spleen, and stomach).

4. Taiyin Spleen Deficiency: Nourishing the Earth to Generate Metal

• Tongue Image: Pale and swollen tongue, teeth marks on the edges, white and greasy coating.
• Classic Formulas:
  • Si Jun Zi Tang (Ginseng + Atractylodes + Poria + Licorice to strengthen the spleen and benefit qi).
  • Shen Ling Bai Zhu San (Enhanced to remove dampness and stop diarrhea).

5. Shaoyin Heart and Kidney: Restoring Yang and Rescuing from Collapse

• Tongue Image: Pale purple tongue, gray-black coating, deep and slow pulse.
• Classic Formulas:
  • Si Ni Tang (Aconite + Dried Ginger + Honey-fried Licorice to restore yang and rescue from collapse).

6. Jueyin Liver Reversal: Harmonizing Yin and Yang

• Tongue Image: Crimson tongue, yellow and dry coating, wiry and hesitant pulse.
• Classic Formulas:
  • Wu Mei Wan (Black Plum + Coptis + Aconite, using both cold and hot to harmonize Jueyin).

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IV. Modern Misinterpretations and Return to the Classics

(With Analysis of Clinical Cases)
1. Common Misconceptions

• Misconception One: “The six meridians are just six meridians” → Truth: The six meridians are dynamic energy layers, encompassing meridians, viscera, and qi transformation functions.
• Misconception Two: “Yangming meridian rich in qi and blood = can sweat freely” → Risk: Depleting body fluids, worsening yin deficiency (Case: A patient overused Ma Huang Tang, leading to worsened constipation).

2. Return to the Classics: Six Meridians Syndrome Differentiation for Children’s Cough

• Case: A 4-year-old child coughs after catching a cold, with a pale tongue, white coating, and floating and tight pulse.
• Mistreatment: Using only cough syrup (treating the symptoms but not the root cause).
• Correct Treatment: Gui Zhi Tang + Fu Ling Xing Ren Gan Cao Tang (relieving the exterior and clearing the lungs + strengthening the spleen and removing dampness), cough stopped after 3 doses.