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Guizhi Tang (Cinnamon Twig Decoction)

Guizhi Tang is the premier formula among Zhang Zhongjing's numerous prescriptions. It is the comprehensive formula for nourishing yin and harmonizing yang, releasing the muscle layer to induce sweating, and harmonizing Ying (Nutritive Qi) and Wei (Defensive Qi). For conditions such as Wind Strike (Zhong Feng), Cold Damage (Shang Han), or miscellaneous diseases presenting with a floating and weak pulse, spontaneous sweating, and unresolved exterior syndrome, this formula serves as the primary treatment. Predecessors stated that Guizhi Tang should not be used when there is no sweat, precisely because the decoction contains Shaoyao (Paeoniae Radix Alba), which can stop sweating. The function of Shaoyao lies in relieving irritability; once irritability is resolved, sweating also ceases. Therefore, for symptoms such as paradoxical irritability, worsening irritability, and palpitations accompanied by irritability, reliance is placed on Shaoyao. If the dosage of Shaoyao is doubled, it transforms into a Jianzhong (Establish the Middle) type formula, rather than a formula for inducing sweating again. In this formula, Guizhi (Cinnamomi Ramulus) is used to induce sweating, while simultaneously Shaoyao is used to stop sweating! The pungency of Shengjiang (Zingiberis Rhizoma) assists Guizhi in releasing the muscle layer; the sweetness of Dazao (Jujubae Fructus) assists Shaoyao in harmonizing the interior. The mutual synergy of Guizhi and Shaoyao, and the proper combination of Shengjiang and Dazao, allow the exterior (Yang) and interior (Yin) to proceed without contradiction. This represents the harmonization achieved through the mutual supplementation of rigidity and softness. Gancao (Glycyrrhizae Radix et Rhizoma) is sweet and neutral, possessing the ability to stabilize the interior and repel external pathogens. It is used to harmonize Qi and Blood, thereby harmonizing the exterior and interior, and also to harmonize the various herbs in the prescription. The profound essence of this formula further lies in drinking hot thin porridge to assist the medicinal power. When grain Qi is充盈 (full) within, pathogens cannot re-enter. Drinking porridge after taking the medicine ensures that residual pathogens do not remain. Thus, the subtle application of compound formulas is demonstrated here. It must be understood that this formula specifically treats Exterior Deficiency Syndrome, capable of releasing the muscle layer to induce sweat from the Ying level, but it cannot open the pores of the skin to expel pathogens from the Wei level. Therefore, absence of sweating indicates a Mahuang Tang (Ephedra Decoction) syndrome, and a floating-tight pulse indicates a Mahuang Tang pulse; in such cases, Guizhi Tang should not be administered. ○ When Guizhi alone is insufficient to overcome wind pathogens, one should first puncture Fengchi (GB20) and Fengfu (GV16), then administer Guizhi Tang to dispel wind. When burning needle therapy is insufficient to disperse cold, one should first moxa the needle sites, then administer Guizhi Jia Gui Tang (Guizhi Decoction with Added Cinnamon Twig) to disperse cold. These are methods of attacking from both inside and outside, illustrating the principle of treating the exterior first and the interior subsequently. Adding Shaoyao to Guizhi Tang treats the sinking of Yang pathogens, while adding more Guizhi to Guizhi Tang treats the attacking upward of Yin pathogens. The subtlety lies in adjusting the dosage of a single herb within the formula, without seeking other ingredients outside the base formula, demonstrating a method that is neither too close nor too distant. ○ After taking Guizhi Tang, if profuse sweating occurs accompanied by severe irritability and thirst, this indicates Yang sinking into the interior. Immediate nourishment of Yin is required, so Baihu Jia Renshen Tang (White Tiger Decoction with Added Ginseng) is used to harmonize it. After using Mahuang Tang, if sweating continues unceasingly, this indicates Yang collapsing at the exterior. Immediate support of Yang is required, so Guizhi Jia Fuzi Tang (Guizhi Decoction with Added Aconite Root) is used to consolidate it. It must be known that in diaphoretic agents, excessive use of Guizhi causes Yang to sink into the interior, while excessive use of Mahuang causes Yang to collapse at the exterior. Because Guizhi Tang contains Shaoyao but lacks Mahuang, even with profuse sweating, the Yuan Fu (pores/sweat gates) can still close themselves, ensuring Yang remains abundant without leading to Yang collapse. ○ Whenever cold pathogens invade the body, if they do not enter Ying and Wei, they enter the Cou Li (interstices). Zhang Zhongjing formulated Guizhi Tang to harmonize Ying and Wei, and Chaihu Tang (Bupleuri Decoction) to harmonize the Cou Li. Observing the Six Meridian syndromes, Zhang Zhongjing uniquely designated "Guizhi Syndrome" and "Chaihu Syndrome," indicating that these two formulas bear significant responsibility and cannot be confined strictly to meridians. Only Taiyang governs the Qi of all Yang meridians, and all exterior syndromes of the Six Meridians belong to Taiyang. Therefore, Chaihu Tang stands in correspondence with Guizhi Tang within the Taiyang sector. Guizhi Tang was originally established for Taiyang Wind-Cold; for any pathogen initially affecting the Six Meridians that has not yet left Ying and Wei, it is suitable. Chaihu Tang was originally established for Shaoyang Half-Exterior/Half-Interior; for any pathogen of the Three Yang meridians lingering in the Cou Li, it is suitable. Zhang Zhongjing valued these two formulas most highly, hence he provided annotations specifically for Guizhi Syndrome and Chaihu Syndrome. Guizhi Tang has ambiguous syndromes, and Chaihu Tang also has ambiguous syndromes. Guizhi Tang syndromes can deteriorate (Hua Bing), and Chaihu Tang syndromes can also deteriorate. When the Guizhi Syndrome resolves and Guizhi Tang is no longer indicated, treatment follows the syndrome, yet still relies on modifications of the Guizhi Tang formula. When the Chaihu Syndrome resolves and Chaihu Tang is no longer indicated, methods to rescue adverse transformations are employed, yet still remain within the scope of modifications of the Chaihu Tang formula. (Ke Yunbo)

Mahuang Tang (Ephedra Decoction)

The Mahuang formula, combined with half the dosage of Guizhi, induces slight sweating; adding Shigao (Gypsum Fibrosum), Shengjiang, and Dazao clears fire and relieves irritability while releasing the exterior; removing the pungent heat of Guizhi and adding the pungent coolness of Shigao clears fire and calms wheezing while releasing the exterior; using Wen Ge (Clam Shell) as the sovereign herb dispels internal and external damp-heat while releasing the exterior; adding bitter-cold herbs like Lianqiao (Forsythiae Fructus) clears fire and treats jaundice while releasing the exterior; adding the great pungent-hot properties of Fuzi (Aconiti Lateralis Radix Praeparata) and Xixin (Asari Radix et Rhizoma), or the pungent-sweet nature of Fuzi and Gancao, depends on the severity of the Shaoyin interior-exterior condition, and is not restricted merely to times of severe cold. Physicians generally assert that Mahuang should not be used lightly, failing to appreciate the divine transformation of Zhang Zhongjing. ○ Predecessors stated that Mahuang Tang primarily treats Shang Han (Cold Damage) and does not treat Zhong Feng (Wind Strike), which seems an inaccurate conclusion. In fact, Mahuang Tang and Da Qing Long Tang (Great Azure Dragon Decoction) are heavy-dose formulas for treating Zhong Feng; Guizhi Tang and Gegen Tang (Kudzu Decoction) are light-dose formulas for treating Zhong Feng. These can be commonly used for Shang Han, but they are not exclusively formulas for treating Shang Han. ○ The Mahuang Tang syndrome, characterized by fever and bone/joint pain, indicates injury by both Wind and Cold, affecting both Ying and Wei. Why did predecessors argue that Da Qing Long Tang treats simultaneous Ying-Wei injury, Mahuang Tang treats Cold injuring Ying without injuring Wei, and Guizhi San treats Wind injuring Wei without injuring Ying? Why not cross-reference the aversion to cold in Guizhi syndrome with the aversion to wind in Mahuang syndrome? Essentially, Wind and Cold in winter share the same origin; thus, both Zhong Feng and Shang Han present with aversion to wind and cold. If Ying is diseased, Wei must also be diseased. Severe Zhong Feng is equivalent to Shang Han; mild Shang Han is equivalent to Zhong Feng. There is no need to distinguish finely between Wind and Cold; one must focus on the presence or absence of sweating. (Ke Yunbo)

Zhang Zhongjing treated Shang Han by using Mahuang Tang for absence of sweat and Guizhi Tang for presence of sweat. Famous physicians of subsequent generations failed to investigate its subtleties. I have pondered this and seem to have gained some insight. It is said that Body Fluids transform into sweat, and sweat is essentially blood. Within Ying, it is called blood; within Wei, it is called sweat. When Cold injures Ying, Ying-Blood becomes stagnant internally and cannot communicate externally with Wei. Wei-Qi closes and secures, Body Fluids fail to circulate, resulting in absence of sweat, fever, and aversion to cold. When Wind injures Wei, Wei-Qi leaks externally and cannot protect Ying internally. Ying-Qi becomes deficient, Body Fluids fail to secure, resulting in presence of sweat, fever, and aversion to wind. However, Wind and Cold pathogens enter via the skin and hair, which are the exterior correspondences of the Lung. The Lung governs Wei-Qi and envelops the entire body, resembling the image of Heaven. Although this syndrome belongs to Taiyang, the Lung actually receives the pathogenic qi. Symptoms including flushed face, depression, cough, phlegm-wheezing, and chest fullness indicate Lung disease. Generally, when the exterior skin and hair close, pathogenic heat attacks internally, causing Lung Qi stagnation. Therefore, Mahuang and Gancao, assisted by Guizhi, draw out pathogens from the Ying level to the muscle surface, assisted by Xingren (Armeniacae Semen Amarum) to drain the Lung and promote Qi flow. Thus, although Mahuang Tang is a heavy diaphoretic agent for Taiyang, it is essentially a medication for dispersing Fire Stagnation in the Lung Meridian. (Li Shizhen)

Gegen Tang (Kudzu Decoction)

Gegen (Puerariae Lobatae Radix) is a herb of the Yangming Meridian. It is suitable only for Exterior Excess and Interior Deficiency, and is not suitable for Yangming Organ Excess (Stomach Excess). Therefore, Zhang Zhongjing rarely uses Gegen in Yangming meridian treatments. If one argues it is avoided because it consumes Body Fluids, this contradicts the materia medica description of Gegen generating fluids. If one argues it greatly opens the muscles, why is it added to combinations involving sweating and aversion to wind? Whether there is sweat or not, whether there is diarrhea or not, Gegen can serve as the principal treatment. This shows that Gegen and Guizhi are both formulas for releasing the muscle layer and harmonizing the middle, differing from Mahuang which specializes in releasing the exterior. ○ Zhang Zhongjing did not use Gegen in Yangming treatments, yet Li Dongyuan classified it as a Yangming herb, and Yi Lao (Wang Haogu) stated: "Do not take it before entering Yangming." Did these two masters not read Zhang Zhongjing's books? (Ke Yunbo)

Da Qing Long Tang (Great Azure Dragon Decoction)

The syndrome of Da Qing Long Tang has remained unclear to the world since Xu Shuwei initiated the misunderstanding. He stated: Guizhi Tang treats Zhong Feng, Mahuang Tang treats Shang Han, and Da Qing Long Tang treats Zhong Feng presenting with Cold pulses, or Shang Han presenting with Wind pulses. These three stand like a tripod, forming the source of these three major outlines. I propose analyzing by pulse first: Zhong Feng pulse floating-tight, Shang Han pulse floating-slow—this is Zhang Zhongjing’s use of parallel prose to imply meaning. It means Zhong Feng pulses are mostly slow, but can be tight; Shang Han pulses should be tight, but can be slow. Generally, Zhong Feng and Shang Han have varying depths, differing due to individual strength, geographical altitude, or seasonal harmony/disorder. Syndromes cannot be rigidly fixed, nor can pulses be dogmatically interpreted. For example, Yangming Zhong Feng may present with a floating-tight pulse, and Taiyang Shang Han may present with a floating-slow pulse; one cannot claim tight pulse necessarily means Shang Han, or slow pulse necessarily means Zhong Feng. According to: *Neijing* states slippery pulse indicates Wind, so Wind pulse has no fixed image; strong and tight indicates distension, so tight pulse does not exclusively indicate Shang Han; slow and slippery indicates Heat in the Middle, so slow pulse does not exclusively indicate Zhong Feng. Moreover, Yangming Zhong Feng presents with floating-tight or floating-large pulses. If one insists floating-slow pulse defines Zhong Feng, what would those two cases be? Current practitioners only differentiate Wind and Cold, Ying and Wei based on Taiyang slow pulse with spontaneous sweat versus tight pulse without sweat, ignoring that all meridians can have Zhong Feng, including Yangming Zhong Feng, which is rarely discussed. Let us speak of Taiyang: The Taiyang chapter describes two Zhong Feng pulse-syndromes: 1) Taiyang Zhong Feng, floating Yang and weak Yin, Yang floating means heat spontaneously arises, Yin weak means sweat spontaneously exits, shivering aversion to cold, chilly aversion to wind, mild fever, nasal congestion, dry vomiting—treated with Guizhi Tang. 2) Taiyang Zhong Feng, floating-tight pulse, fever, aversion to cold, body pain, no sweat, irritability—treated with Da Qing Long Tang. Comparing these two: Floating Yang indicates mild cold, floating-tight indicates severe cold; sweating indicates mild cold, no sweat indicates severe cold; shivering/chilly indicates mild Wind-Cold, mild fever indicates mild heat; nasal congestion indicates mild Wind, body pain indicates severe Wind; spontaneous sweat/dry vomiting indicates mild irritability, no sweat/irritability indicates severe irritability. Regarding Shang Han pulse-syndromes: 1) Taiyang Disease, either no fever or already fever, must have aversion to cold, body pain, vomiting/reversal, pulse tight at both Yin and Yang positions—named Shang Han. 2) Shang Han, floating pulse, spontaneous sweat, frequent urination, irritability, slight aversion to cold, foot cramping. Comparing these two: Slight aversion to cold indicates severe aversion to cold; body pain indicates mild cramping; spontaneous sweat/frequent urination/irritability indicates mild Shang Han; no fever indicates difficulty in fever onset; vomiting/reversal indicates severe Shang Han; floating pulse indicates mild cold, tight Yin-Yang pulse indicates severe cold. Thus, Zhong Feng and Shang Han have varying degrees of severity. Current practitioners insist Shang Han is severe and Zhong Feng is mild, knowing only to distinguish Wind/Cold invasion but not their severity, leading to excuses like "Shang Han showing Wind signs, Zhong Feng showing Cold signs." Synthesizing this, one cannot define Zhong Feng solely by slow pulse and sweat, nor define Shang Han solely by tight pulse and no sweat. It must be known that Zhang Zhongjing diagnoses based on pulse and syndrome, focusing only on Deficiency and Excess. Regardless of Zhong Feng or Shang Han, if the pulse is tight or slow but forceful under the fingers, it is Excess; if weak and powerless, it is Deficiency; no sweat with irritability is Excess; profuse sweat with irritability is Deficiency; irritability in Taiyang is Excess; irritability in Shaoyin is Deficiency. Excess patterns can take Da Qing Long Tang; Deficiency patterns must not. This is easy to understand. It must be known that Zhang Zhongjing formulates based on syndrome, not solely on pulse. Da Qing Long Tang is established for Wind-Cold at the exterior combined with internal Heat, not solely for absence of sweat. Therefore, it can be used for Zhong Feng with irritability, and for Shang Han with irritability. Since Wind and Cold share the same origin, the decoctions can be interchangeable. The text mentions Zhong Feng and Shang Han interchangeably, as seen in Da Qing Long Tang; and together, as seen in Xiao Chai Hu Tang. Zhang Zhongjing carefully examines pulse and syndrome to apply treatment; how could he be constrained by the names Zhong Feng and Shang Han? ○ The various syndromes of Da Qing Long Tang are based on Mahuang, distinguished by wheezing versus irritability. Wheezing results from Cold stagnating Qi, disrupting ascending and descending functions, hence Xingren’s bitter property is used to descend Qi. Irritability results from Heat damaging Qi and lack of fluids preventing sweat, hence Gypsum’s sweet property is specifically added to generate fluids. ○ In Mahuang Tang syndrome, Heat is entirely at the exterior. Spontaneous sweat in Guizhi Tang syndrome, and irritability in Da Qing Long Tang syndrome, both involve interior Heat. Zhang Zhongjing uses cold medicines within exterior-releasing formulas to clear the interior. Spontaneous sweat is a sign of irritability; irritability is a sign of restlessness. With sweat, irritability can vent outward, so there is no restlessness; mild cold, sour, and bitter flavors are used to harmonize. Without sweat, irritability cannot vent, so restlessness occurs; great cold and heavy substances are used to clear. Shaoyao and Shigao are interior herbs placed in exterior formulas. Modern practitioners, failing to recognize interior involvement in exterior conditions, hesitate and fail to use them when needed, until Heat merges into Yangming, causing macules, jaundice, mania, and confusion. Zhang Zhongjing uses Shigao in Taiyang to clear Stomach Fire, a preemptive move to protect Yangming; adding Jiang and Zao to fortify the Middle Earth prevents transmission to Taiyin. ○ Both Qing Long formulas are methods of resolving both exterior and interior. Da Qing Long Tang treats interior Heat; Xiao Qing Long Tang treats interior Cold. Thus, exterior-releasing herbs are the same, but interior-treating herbs differ. ○ The key point of Da Qing Long Tang lies in the phrases "no sweat, irritability, and no Shaoyin syndrome." ○ Da Qing Long Tang is named a heavy formula; it is not only contraindicated in Shaoyin Shang Han but should also not be used lightly in Taiyang Zhong Feng. Floating-tight pulse with no sweat is a Mahuang Tang syndrome, contraindicated for Guizhi Tang because Shaoyao stops sweat. Floating-weak pulse with spontaneous sweat is a Guizhi Tang syndrome, contraindicated for Da Qing Long Tang because it contains Mahuang and Shigao. (Ke Yunbo)

Xiao Qing Long Tang (Minor Azure Dragon Decoction)

Xiao Qing Long Tang and Xiao Chai Hu Tang are both formulas that resolve both exterior and interior. Xiao Qing Long Tang focuses on interior syndromes; Xiao Chai Hu Tang focuses on exterior syndromes. Therefore, in modifications of Xiao Qing Long Tang, Mahuang can be removed; in modifications of Xiao Chai Hu Tang, Chaihu (Bupleuri Radix) remains unique. This is because Xiao Qing Long Tang focuses on Water-Dampness in the semi-interior, while Xiao Chai Hu Tang focuses on Heat in the semi-exterior. ○ Both Xiao Qing Long Tang and Xiao Chai Hu Tang are pivot mechanisms; thus, both include "possible syndromes" (Huo Ran Zheng) and respective modification methods. Once half the exterior syndrome is resolved, the disease mechanism tends inward. Therefore, the syndromes of these two formulas mostly belong to the interior, and Zhang Zhongjing uses more interior herbs and fewer exterior herbs. Since they have not completely left the exterior, they are called small exterior-resolving formulas. However, Xiao Qing Long Tang governs the semi-exterior/semi-interior of Taiyang and still uses Mahuang and Guizhi, valuing the exterior; Xiao Chai Hu Tang governs the semi-exterior/semi-interior of Shaoyang and uses only Chaihu and Shengjiang, slightly resolving the exterior. This is because the Yang Qi of Taiyang and Shaoyin differs, so the weight of exterior herbs varies. ○ Xiao Qing Long Tang sets five possible syndromes, containing five formulas within its modifications. Xiao Chai Hu Tang sets seven possible syndromes, containing seven formulas within its modifications. This is the method within Zhang Zhongjing’s methods, the formula beyond formulas. ○ Xiao Qing Long Tang and Wu Ling San (Five-Ingredient Powder with Poria) both treat unresolved exterior with Water-Qi under the heart. Wu Ling San treats Water accumulation and stagnation, promoting diuresis and slight sweating, following the *Neijing* principle of "breaking water stagnation"; Xiao Qing Long Tang treats Water movement and instability, employing pungent-warm herbs to scatter Water and sour-bitter herbs to calm the Lung, cultivating the source of transformation. (Ke Yunbo)

Shi Zao Tang (Ten Date Decoction)

Both present with Water-Qi under the heart, dry retching, coughing, and wheezing; one is treated with Xiao Qing Long Tang, the other with Shi Zao Tang. Why? Xiao Qing Long Tang disperses exterior pathogens, allowing Water-Qi to exit via the pores, following the *Neijing* method of "opening the ghost gate" (diaphoresis); Shi Zao Tang drives out interior pathogens, allowing Water-Qi to drain via urination and defecation, following the *Neijing* method of "cleaning the residence" (diuresis/catharsis). ○ Previously, Du Ren asked Sun Zhao: "What disease does Shi Zao Tang ultimately treat?" Sun replied: "It treats Taiyang Zhong Feng where the exterior is resolved but the interior is not harmonized." Du asked: "How do you know the interior is not harmonized?" Sun said: "Headache, epigastric fullness/stuffiness, hypochondriac pain, dry retching, sweating—these indicate the interior is not harmonized." Du said: "You only mentioned the syndrome, but not the crucial reason why the interior is not harmonized." Sun said: "I have been undecided on this; I wish to hear your enlightenment." Du said: "The interior is not harmonized because Phlegm and Water-Qi are congested in the Middle Jiao, causing headache, dry retching, shortness of breath, and sweating. This is Phlegm Obstruction. Only Shi Zao Tang can treat it. But this decoction should not be used lightly, as it may harm the patient suddenly. Users must be cautious!" (Yu Jiayan)

Wu Ling San (Five-Ingredient Powder with Poria)

In Shang Han, Wu Ling San is appropriately used when Taiyang Cold Pathogen invades the root, with Heat in the Bladder; thus, it promotes water drainage and dissipates Heat. The use of Guizhi here is to disseminate pathogens and continue treating Taiyang. In miscellaneous diseases, Wu Ling San is used specifically for Bladder Deficiency with Cold-Water congestion; thus, Rougui (Cinnamomi Cortex) is used as the sovereign herb to enable the circulation and discharge of Deficient-Cold Qi. The usage for these two conditions differs slightly and must be distinguished. (Luo Dongyi)

If one wishes to use Wu Ling San to release the exterior, hot drink travels to the exterior, and Guizhi takes command; if one wishes to promote urination, cold drink reaches the lower part, and Zexie (Alismatis Rhizoma) takes command. If one wishes to induce vomiting, warm administration followed by hot water probing allows Zhu Ling (Polypori Mycelium) to take command. Such infinite subtle applications exist within one formula. (*Shen Zhai San Shu*)

Wu Ling San originally treats Water, not Thirst. It is used to dissipate ingested Water, not to treat Irritable Thirst or Wasting-Thirst (Xiao Ke). Moreover, Wu Ling San focuses on Internal Irritability and External Heat; using Guizhi is to drive out Water to relieve irritability, not "treating heat with heat." It induces slight sweating to resolve the exterior, not assisting Si Ling (the four draining herbs) to promote urination. Its use of Si Ling is to move accumulated water and retained turbidity, not merely to unblock water pathways. (Ke Yunbo)

Wu Ling San combines exterior treatment methods; Zhu Ling San specializes in interior treatment methods. If one desires pathogens to penetrate the exterior, Wu Ling San resolves from above, known as "opening the ghost gate"; if one desires pathogens to渗 (seep) downward, Zhu Ling San resolves from below, known as "cleaning the residence." (Wei Litong)

Zhu Xi Xin Tang (Various Heart-Draining Decoctions)

*Neijing* states: Above the waist is Yang. Therefore, the Three Yang meridians all have Heart and Chest diseases. Zhang Zhongjing established Xi Xin Tang to treat the Three Yang separately. In Taiyang, using Shengjiang as sovereign is because there was no erroneous purgation, yet Pi (Glomus/Stuffiness) formed under the heart; although sweat occurred and exterior resolved, Water-Qi had not dispersed, so it subtly incorporates the meaning of releasing the muscle layer. In Yangming, using Gancao as sovereign is because of double erroneous purgation leaving the Stomach empty, making Pi worse; thus, doubling Gancao establishes the Middle and slows the counterflow of guest pathogens, also a method of treating from the center. In Shaoyang, using Banxia (Pinelliae Rhizoma) as sovereign is because erroneous purgation caused Pi, pathogens have left the semi-exterior (so Chai Hu Tang is no longer suitable), and have not fully entered the interior (so Huang Qin Tang is no longer suitable). To treat Pi under the heart, soft upon pressure, with pulse floating at the Guan position, use Da Huang Huang Lian Xi Xin Tang (Rhubarb and Coptis Heart-Draining Decoction); for Pi under the heart accompanied by aversion to cold and sweating, use Fu Zi Xi Xin Tang (Aconite Heart-Draining Decoction). These are all excess-draining agents. Although sharing the name with the previous three formulas, their methods differ. ○ Zhang Zhongjing’s method for Xi Xin has no fixed rule. If Righteous Qi is depleted, it becomes Deficient Pi, treated with a mix of Sweet-Nourishing, Pungent-Dispersing, Bitter-Draining, and Cold-Warming items to harmonize. If Pathogenic Qi is abundant, it becomes Excess Pi, treated with Great Cold, Great Hot, Great Bitter, and Great Pungent flavors to drain. Harmonizing has degrees of lightness/heaviness; draining has distinctions of cold/warmth. Named similarly as Heart-Draining, but the prescribed formulas differ thus. However, among the five formulas, the number and dosage of herbs vary in each, except Huanglian (Coptidis Rhizoma) which remains fixed. This is because its bitterness enters the Heart first; hollow inside and connected outside, it can unblock the cold and heat of other herbs, making it the main agent for Heart-Draining. (Ke Yunbo)

Xi Xin was originally named Lizhong Huanglian Renshen Tang (Regulate the Middle, Coptis, and Ginseng Decoction). Treating Pi with Xi Xin is precisely the process of Regulating the Middle. One must know Zhang Zhongjing uses two methods in Lizhong: one to Support Yang, one to Benefit Yin. (Lin Yi)

Middle Deficiency fails to transform Qi, causing Yin to rebel downward and Yang to block upward. This is also Pathogen residing in the semi-exterior/semi-interior. Transforming Xiao Chai Hu Tang into Banxia Xi Xin Tang... [Text cuts off]