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In all diseases, there are names and symptoms, mechanisms and conditions. For example, wind-stroke (Zhongfeng), cold damage (Shanghan), warm diseases (Wenbing), summerheat diseases (Shu Bing), dampness diseases (Shi Bing), and spasm diseases (Jing Bing) belong to the category of "names" (disease nomenclature). External manifestations include headache, body pain, and lower back pain; internal manifestations include wheezing and coughing, vexation and thirst, vomiting and diarrhea, and abdominal fullness. These constitute the "symptoms" (Zheng). The location of the pathogen in the exterior or interior, the presence or absence of sweating, the pulse being floating or sunken, and the pulse force being strong or weak, represent the "mechanism" (Ji - key pathological mechanism). At this time, aversion to cold or heat, chest and hypochondriac fullness with a tendency to vomit, ability or inability to eat, desire to sleep but inability to do so, drinking several liters of water, or swishing water in the mouth without swallowing, are all "conditions" (Qing - specific clinical presentations). Formulating prescriptions based solely on disease names is the work of crude physicians; determining prescriptions based on symptoms is the work of average physicians; examining the pathological mechanism and observing the clinical condition within the symptoms is the work of excellent physicians. Zhang Zhongjing formulated prescriptions without being bound by disease names, but only by seeking accuracy in symptoms. By mastering the mechanism and understanding the condition, for any wind-stroke, cold damage, or miscellaneous disease, he would select the appropriate prescription effortlessly, employing flexible methods without exception. This is what is meant by "physicians do not adhere rigidly to fixed prescriptions." Today, those who discuss Zhongjing's prescriptions claim that Guizhi Tang (Cinnamon Twig Decoction) treats wind-stroke but not cold damage, and Mahuang Tang (Ephedra Decoction) treats cold damage but not wind-stroke. They fail to examine which symptoms Zhongjing's prescriptions primarily address, nor do they analyze which herbs Zhongjing used for specific symptoms. Instead, they merely compare wind-stroke and cold damage symptoms and speculate on names like Qinglong (Azure Dragon) and Baihu (White Tiger), thereby turning Zhongjing's flexible prescriptions and methods into rigid ones.

Zhongjing's prescriptions are exquisite and non-mixed, with six main formulas serving as the foundation from which others are modified. All diaphoretic (sweating-inducing) prescriptions are based on Guizhi Tang (Cinnamon Twig Decoction); all emetic prescriptions are based on Zhizi Chidao Tang (Gardenia and Fermented Soybean Decoction); all purgative prescriptions are based on Chengqi Tang (Order the Qi Decoction); all harmonizing prescriptions are based on Chaihu Tang (Bupleurum Decoction); all cooling prescriptions are based on Xiexin Tang (Drain the Epigastrium Decoction); and all warming prescriptions are based on Sini Tang (Reverse the Extremities Decoction). The count of one hundred and thirteen prescriptions mixed together results from a lack of careful examination.

Each of the Six Meridians has its primary governing prescription, yet there is subtle mutual applicability among them. For instance, Mahuang Tang (Ephedra Decoction) and Guizhi Tang (Cinnamon Twig Decoction) were established for Taiyang (Greater Yang) disharmony of Ying (Nutrient) and Wei (Defensive) levels, yet they are also used when Yangming (Yang Brightness) pathology involves the Ying and Wei levels. Zhenwu Tang (True Warrior Decoction) was established for Shaoyin (Lesser Yin) water qi pathology, yet it is also used for Taiyang pathology involving yang collapse after sweating. Sini Tang (Reverse the Extremities Decoction) was established for Taiyin (Great Yin) diarrhea with undigested food, yet it is suitable for Taiyang pathology where the pulse is unexpectedly sunken. Wuling San (Five-Ingredient Powder with Poria) was established for Taiyang polydipsia and water regurgitation, yet it is also suitable for Yangming pathology involving excessive water intake. Zhuling Tang (Poria Decoction) was established for Shaoyin diarrhea, yet it is also suitable for Yangming pathology involving difficult urination. Didang Tang (Arriving at the Blood Stasis Decoction) was established for Taiyang blood stasis in the interior, yet it is also used for Yangming blood accumulation. Gouti San (Melon Tip Powder) was established for Yangming epigastric hardness and oppression, yet it is also used for Shaoyin pathology involving a persistent urge to vomit. When symptoms match, the corresponding prescription is used. Although each prescription belongs to a specific meridian, its application need not be restricted. This is Zhongjing's method. Zhongjing's prescriptions differ only in terms of exterior/interior, cold/heat, and deficiency/excess, without distinct separation between cold damage, wind-stroke, or miscellaneous diseases. There is a subtlety in alternating two prescriptions for wind-cold, and a uniqueness in exchanging two prescriptions for exterior/interior issues. Some achieve success with the complete formula, while others achieve results through modifications. Later scholars discussed prescriptions without analyzing symptoms, making Zhongjing's prescriptions seem difficult to use. Guizhi Tang (Cinnamon Twig Decoction) is the premier diaphoretic agent. Mahuang (Ephedrae Herba) penetrates directly through the skin and hair follicles, while Shengjiang (Zingiberis Rhizoma Recens) disperses horizontally through the muscles. Therefore, when Guizhi Tang (Cinnamon Twig Decoction) assists Mahuang Tang (Ephedra Decoction), it opens the Xuankou (pores) and expels pathogens from the Wei (Defensive) level, inducing sweating in those who have none, thus termed "inducing sweating." When Guizhi Tang (Cinnamon Twig Decoction) leads Shengjiang (Zingiberis Rhizoma Recens), it opens the Couli (interstices) and drives out pathogens from the Ying (Nutrient) level, inducing sweating in those who already sweat, thus termed "releasing the muscle layer." Releasing the muscle layer means resolving pathogens in the muscle layer, which resides in the Ying level. Why do proponents of the "Three Guidelines" theory claim Mahuang manages Ying and Guizhi manages Wei? Mahuang Tang does not explicitly mention releasing the muscle layer, yet the muscle layer is invariably resolved; Guizhi Tang's release of the muscle layer is precisely how it induces sweating. It must be understood that Mahuang Tang (Ephedra Decoction) and Guizhi Tang (Cinnamon Twig Decoction) represent methods of inducing sweating at different depths. Sweating should not be attributed solely to Mahuang, nor should releasing the muscle layer be contrasted against inducing sweating. Previous scholars discussed these two prescriptions as topics of conversation rather than using them clinically.

When wind-cold invades the human body, if it does not enter the Ying and Wei levels, it enters the Couli (interstices). Zhongjing formulated Guizhi Tang (Cinnamon Twig Decoction) to harmonize Ying and Wei, and Chaihu Tang (Bupleurum Decoction) to harmonize the Couli. Observing the Six Meridians' symptoms, Zhongjing uniquely coined the terms "Guizhi Syndrome" and "Chaihu Syndrome," indicating that these two prescriptions bear significant responsibility and cannot be confined to a single meridian. Only the Taiyang (Greater Yang) meridian governs the Qi of all Yang meridians, and all exterior syndromes of the Six Meridians belong to Taiyang. Thus, Chaihu Tang (Bupleurum Decoction) stands in opposition to Guizhi Tang (Cinnamon Twig Decoction) within the Taiyang sector. Guizhi Tang (Cinnamon Twig Decoction) was originally established for Taiyang wind-cold; it is suitable for any initial external pathogen affecting the Six Meridians that has not yet left the Ying and Wei levels. Chaihu Tang (Bupleurum Decoction) was originally established for Shaoyang (Lesser Yang) semi-exterior/semi-interior locations; it is suitable for any pathogen of the Three Yang meridians lingering in the semi-exterior/semi-interior Couli. Zhongjing valued these two prescriptions highly, providing annotations for both Guizhi Syndrome and Xiao Chaihu Tang (Minor Bupleurum Decoction). Both Guizhi and Chaihu syndromes have ambiguous presentations. Both can develop into "transformed diseases" (Huabing). Once the Guizhi syndrome resolves, Guizhi Tang (Cinnamon Twig Decoction) is no longer applicable, but subsequent treatments still rely on modifications of the Guizhi Tang (Cinnamon Twig Decoction) formula. Once the Chaihu syndrome resolves, Xiao Chaihu Tang (Minor Bupleurum Decoction) is no longer applicable, but rescue methods still rely on modifications of the Xiao Chaihu Tang (Minor Bupleurum Decoction) formula.

Mahuang Tang (Ephedra Decoction) syndrome features heat entirely in the exterior. Guizhi Tang (Cinnamon Twig Decoction) syndrome features spontaneous sweating, and Da Qinglong Tang (Major Azure Dragon Decoction) syndrome features vexation and restlessness; both involve interior heat. In exterior-releasing formulas, Zhongjing incorporates cold-natured herbs to clear interior heat. Spontaneous sweating is a precursor to vexation; restlessness is a sign of vexation. When sweating occurs, vexation can dissipate outward, so restlessness does not occur; mild cold, sour, and bitter flavors are used to harmonize. When sweating does not occur, vexation cannot dissipate, leading to restlessness; major cold and heavy substances are used to clear heat. Shaoyao (Paeoniae Radix Alba) and Shigao (Gypsum Fibrosum) are interior herbs included in exterior formulas. Modern practitioners, failing to recognize interior involvement in exterior patterns, hesitate and fail to use them, allowing heat to merge into the Yangming stage, resulting in macules, jaundice, mania, and confusion. This failure is due to an inability to appropriately use Da Qinglong Tang (Major Azure Dragon Decoction). Zhongjing uses Shigao (Gypsum Fibrosum) in the Taiyang meridian to clear stomach fire, a preemptive measure to protect the Yangming meridian; adding Jiang (Zingiberis Rhizoma) and Zao (Jujubae Fructus) nourishes the middle, anticipating potential transmission to the Taiyin meridian.

Xiao Qinglong Tang (Minor Azure Dragon Decoction) and Chaihu Tang (Bupleurum Decoction) are both exterior-interior dual-resolving formulas. Xiao Qinglong Tang (Minor Azure Dragon Decoction) focuses on interior symptoms, while Xiao Chaihu Tang (Minor Bupleurum Decoction) focuses on exterior symptoms. Therefore, in modifications of Xiao Qinglong Tang (Minor Azure Dragon Decoction), Mahuang (Ephedrae Herba) may be removed; in modifications of Xiao Chaihu Tang (Minor Bupleurum Decoction), Chaihu (Bupleuri Radix) remains unique. This is because Xiao Qinglong Tang (Minor Azure Dragon Decoction) focuses on water retention in the semi-interior, while Xiao Chaihu Tang (Minor Bupleurum Decoction) focuses on heat in the semi-exterior. Xiao Qinglong Tang (Minor Azure Dragon Decoction) treats water qi from unresolved cold damage, using warm agents to induce sweating and disperse; Shizao Tang (Ten Jujube Decoction) treats water qi from resolved wind-stroke, using cold agents to guide and exhaust the pathogen. This illustrates the different treatments for cold-water and wind-water pathologies. The water treated by Xiao Qinglong Tang (Minor Azure Dragon Decoction) is moving and unsettled; the water treated by Wuling San (Five-Ingredient Powder with Poria) is stagnant and immobile; the water treated by Shizao Tang (Ten Jujube Decoction) is unrestrained; the water treated by Daxiexiong Tang (Major Chest Trap Decoction) presents as oppression, hardness, firmness, and fullness; the water treated by Zhenwu Tang (True Warrior Decoction) causes heaviness in the four limbs. Since water pathologies vary, treatment methods differ.

Lin Yi stated: "Xiexin Tang (Drain the Epigastrium Decoction) was originally named Lizhong Huanglian Renshen Tang (Spleen-Nourishing Coptis and Ginseng Decoction), as treating epigastric obstruction with Xiexin Tang (Drain the Epigastrium Decoction) aligns with the function of Lizhong Tang (Regulate the Middle Decoction)." One must understand that Zhongjing used Lizhong Tang (Regulate the Middle Decoction) with both cold and heat methods: one to support Yang, the other to benefit Yin. When pathogens reside between Ying and Wei, sweating is the only exit, hence Mahuang Tang (Ephedra Decoction) and Guizhi Tang (Cinnamon Twig Decoction) were established. When pathogens reside between the chest and abdomen, vomiting is the only exit, hence Gouti San (Melon Tip Powder) and Zhizi Chi Dao Tang (Gardenia and Fermented Soybean Decoction) were established. Gouti San (Melon Tip Powder) treats epigastric hardness and oppression, addressing the Upper Jiao (Upper Burner); Zhizi Chi Dao Tang (Gardenia and Fermented Soybean Decoction) treats abdominal fullness and wheezing, addressing the Middle Jiao (Middle Burner). This parallels Mahuang Tang (Ephedra Decoction) targeting the skin and Guizhi Tang (Cinnamon Twig Decoction) targeting the muscles. Gouti San (Melon Tip Powder) is a harsh agent, similar to Mahuang Tang (Ephedra Decoction) which should not be used lightly; Zhizi Chi Dao Tang (Gardenia and Fermented Soybean Decoction) is a mild agent, similar to Guizhi Tang (Cinnamon Twig Decoction) which can be reused without harm. Thus, Taiyang exterior formulas often modify Guizhi Tang (Cinnamon Twig Decoction); Yangming exterior formulas often modify Zhizi Chi Dao Tang (Gardenia and Fermented Soybean Decoction). Using Zhizi Chi Dao Tang (Gardenia and Fermented Soybean Decoction) in Yangming is like using Guizhi Tang (Cinnamon Twig Decoction) in Taiyang: just as it can expel pathogens, it can also rescue deviations. Modern practitioners know only that sweating resolves the exterior, unaware that vomiting also resolves the exterior. They know the saying that vomiting contains dispersing properties but do not understand the rationale for vomiting. Consequently, within Zhongjing's great methods, they take sweating and purging but omit vomiting.

Shaoyang (Lesser Yang) acts as the pivot, neither fully interior nor fully exterior. Zhongjing's original intent emphasized the interior, yet Chaihu Tang (Bupleurum Decoction) governs the semi-interior. Therefore, semi-exterior conditions must be present to justify modifying Xiao Chaihu Tang (Minor Bupleurum Decoction). If the pathogen is entirely interior, Chaihu Tang (Bupleurum Decoction) is not indicated, hence it is called an exterior-resolving formula. Although Xiao Chaihu Tang (Minor Bupleurum Decoction) treats semi-exterior conditions, it essentially regulates the Qi of the Three Jiao (Three Burners), earning it the title of "pivot agent." Symptoms such as chest fullness, epigastric vexation, heart vexation, epigastric palpitations, cough, thirst, and a tendency to vomit indicate a lack of developmental mechanism in the Upper Jiao (Upper Burner). Abdominal fullness and hypochondriac hardness indicate a failure of transport mechanism in the Middle Jiao (Middle Burner). Difficult urination indicates a loss of drainage function in the Lower Jiao (Lower Burner). These result from the struggle between pathogenic factors and righteous Qi. Ren Shen (Ginseng Radix et Rhizoma) is used to support the righteous Qi of the Three Jiao (Three Burners) and strengthen the pivot.

In Shaoyin (Lesser Yin) disease lasting two to three days, with heart vexation and inability to sleep, the root pathology lies in the Heart. The method should nourish the true fire within Li (Fire), following its moistening downward trend. Thus, Huang Lian (Coptidis Rhizoma) is used as the sovereign herb for its bitter cold nature to drain heat. On the fourth to fifth day, with difficult urination and pus/blood in stool, the root pathology lies in the Kidney. The method should raise the minor fire within Kan (Water), following its flaming upward trend. Thus, Gan Jiang (Zingiberis Rhizoma) is used as an assistant herb for its bitter warm nature to disperse. This distinguishes the "hidden brightness fire" from the "ascending brightness fire." In Shaoyin (Lesser Yin) disease with vexation and drowsiness, progressing to five to six days with an urge to vomit without success, spontaneous diarrhea with thirst, and white urine, the Lower Jiao (Lower Burner) is deficient and cold, unable to control water. Zhenwu Tang (True Warrior Decoction) is indicated to warm the Kidney water of the Lower Jiao (Lower Burner). With diarrhea lasting six to seven days, accompanied by cough, vomiting, thirst, heart vexation, and insomnia, the Upper Jiao (Upper Burner) has deficient heat, and fluid metabolism is impaired. Zhuling Tang (Poria Decoction) is indicated to unblock the fluids of the Upper Jiao (Upper Burner).

Sini Tang (Reverse the Extremities Decoction) is the principal formula for Taiyin (Great Yin), yet it can be used across meridians. In Taiyin (Great Yin), it consolidates the root to expel pathogens; in Shaoyin (Lesser Yin), it warms Earth to control Water; in Jueyin (Terminal Yin), it harmonizes Earth to generate Wood; in Taiyang (Greater Yang), it benefits Fire to support primal Yang. It is unsuitable for Yangming (Yang Brightness) stomach excess and Shaoyang (Lesser Yang) ministerial fire.

In Shaoyin (Lesser Yin) disease lasting four to five days, with abdominal pain, difficult urination, and incessant diarrhea: if accompanied by heaviness and pain in the four limbs, it indicates Lower Jiao (Lower Burner) water stagnation; Zhenwu Tang (True Warrior Decoction) is used, representing the method of guiding fire back to its source. If accompanied by pus and blood in stool, it indicates Lower Jiao (Lower Burner) fire stagnation; Taohua Tang (Peach Blossom Decoction) is used, representing the method of raising Yang and scattering fire. This is due to deficiency of Yang in Kan (Water); difficult urination should not be treated as heat.

Xiao Chaihu Tang (Minor Bupleurum Decoction) is the principal formula for Shaoyang (Lesser Yang); Wu Mei Wan (Mume Pill) is the principal formula for Jueyin (Terminal Yin). Although different, their methods of combining cold/warm and tonifying/purging are compatible due to connected zang-fu organs, interwoven meridians, shared Wind-Wood Qi, and joint governance of Ministerial Fire. Both use Ren Shen (Ginseng Radix et Rhizoma) to tonify the middle and boost Qi to consolidate the root and expel pathogens. Other ingredients do not overlap due to differing Yin-Yang positions. Yang favors ascending and dispersing, so Chaihu (Bupleuri Radix) is primary; Yin favors gathering and descending, so Wu Mei (Mume Fructus) is primary. Yang governs heat, so cold/cool herbs are heavily used; Yin governs cold, so acrid/warm herbs are heavily used. Yang functions through movement, so decoctions are used to sweep away pathogens; symptoms are variable, hence Xiao Chaihu Tang (Minor Bupleurum Decoction) has modification rules. Yin functions through stillness, so pills are used to缓 (slow/relax); symptoms are fixed, hence Wu Mei Wan (Mume Pill) has no modification rules.

For Jueyin (Terminal Yin) diarrhea, Baitouweng Tang (Pulsatilla Decoction) is used to raise Yang and scatter fire, embodying the principle of "dispersing constrained fire." Wu Mei Wan (Mume Pill) is formulated to gather fire, embodying the meaning of "bending and straightening producing acidity." Bitter-cold herbs harmonize Yin; warm-tonifying herbs preserve Yang. This is the method of regulating Qi in the Liver. Because it treats reversal cold-diarrhea and chronic diarrhea, it half-comprises warm-tonifying elements. Baitouweng Tang (Pulsatilla Decoction) treats wind-heat diarrhea with tenesmus, focusing purely on cooling and dispersing.

Commentary: Releasing the exterior and purging the interior are chief techniques for resisting pathogens. Exterior syndromes are caused by wind-cold; if exterior herbs are cold-natured, exterior heat will not subside, and interior cold will arise. Thus, exterior herbs must include Guizhi (Cinnamomi Ramulus); releasing the exterior does not avoid heat. However, this applies only to Taiyang (Greater Yang) exterior heat. For Yangming (Yang Brightness) and Shaoyang (Lesser Yang) fever, herbs like Chaihu (Bupleuri Radix), Huang Qin (Scutellariae Radix), Zhizi (Gardeniae Fructus), and Chi Xiao Dou (Sojae Semen Praeparatum) should be used. Interior syndromes are caused by constrained heat; if purgatives are not bitter-cold, constrained heat will not be removed, and pathogens will have no exit. Thus, purgative agents must use Da Huang (Rhei Radix et Rhizoma); purging the interior does not avoid cold. However, this applies only to Yangming (Yang Brightness) stomach heat. For aversion to cold, epigastric hardness, and Yang deficiency with Yin binding, herbs like Gan Jiang (Zingiberis Rhizoma), Fu Zi (Aconiti Lateralis Radix Preparata), and Ba Dou (Crotonis Fructus) should be added.

Mahuang Tang (Ephedra Decoction) and Guizhi Tang (Cinnamon Twig Decoction) are exterior herbs for Taiyang (Greater Yang) and Yangming (Yang Brightness) exterior syndromes. Gouti San (Melon Tip Powder) and Zhizi Chi Dao Tang (Gardenia and Fermented Soybean Decoction) are exterior herbs for Yangming (Yang Brightness) interior syndromes. Xiao Chaihu Tang (Minor Bupleurum Decoction) is an exterior herb for Shaoyang (Lesser Yang) semi-exterior syndromes. The exterior herb for Taiyin (Great Yin) is Guizhi Tang (Cinnamon Twig Decoction); for Shaoyin (Lesser Yin), it is Mahuang Fuzi Xixin Tang (Ephedra, Prepared Aconite, and Asarum Decoction); for Jueyin (Terminal Yin), it is Danggui Sini Tang (Angelica Sinensis Decoction for Reversal Cold). The use of exterior herbs in the Six Meridians provides an exit for wind-cold pathogens.

Reversal cold of the hands and feet varies by cold/heat and exterior/interior. Sini San (Bupleurum Powder for Reversal Cold) resolves Shaoyin (Lesser Yin) interior heat; Danggui Sini Tang (Angelica Sinensis Decoction for Reversal Cold) resolves Jueyin (Terminal Yin) exterior cold; Tongmai Sini Tang (Unblocking the Vessels Reverse the Extremities Decoction) rescues the impending collapse of Shaoyin (Lesser Yin) true Yang; Fuling Sini Tang (Poria Reverse the Extremities Decoction) preserves the impending depletion of Taiyin (Great Yin) true Yin. These four formulas differ in severity and depth across meridians.

The Bladder governs water and is the interior of Taiyang (Greater Yang); Shizao Tang (Ten Jujube Decoction) and Wuling San (Five-Ingredient Powder with Poria) are purgatives for the Taiyang (Greater Yang) water pathways. The Stomach governs grain and is the interior of Yangming (Yang Brightness); the three Chengqi Tangs (Order the Qi Decoctions) are purgatives for the Yangming (Yang Brightness) grain pathways. The Gallbladder governs Qi and is the interior of Shaoyang (Lesser Yang); Da Chaihu Tang (Major Bupleurum Decoction) is a purgative for Shaoyang (Lesser Yang) Qi level. These three Yang purgatives provide an exit for excess pathogens in the Three Yang meridians. The Large Intestine and Small Intestine belong to the Stomach; when the Stomach house is excess, both intestines are excess. Dividing them: Tiaowei Chengqi Tang (Regulate the Stomach Order the Qi Decoction) is the purgative for the Stomach house; Xiaochengqi Tang (Minor Order the Qi Decoction) is the purgative for the Small Intestine; Dachengqi Tang (Major Order the Qi Decoction) is the purgative for the Large Intestine. Wu (Earth) is dry soil; Geng (Metal) is dry metal; thus, Mangxiao (Natrii Sulfas) is added to moisten dryness. Guizhi Jiadahuang Tang (Cinnamon Twig Plus Rhubarb Decoction) is a purgative for Taiyang (Greater Yang) transmitting to Yangming (Yang Brightness); Guizhi Jiashao Yao Tang (Cinnamon Twig Plus Peony Decoction) is a purgative for Taiyang (Greater Yang) transmitting to Taiyin (Great Yin).

Purgatives combined with exterior herbs are used because the pathogen has not fully left the exterior. Chaihu Jianiaoxiao Tang (Bupleurum Plus Natrii Sulfas Decoction) is a purgative for Shaoyang (Lesser Yang) transmitting to Yangming (Yang Brightness). Da Chaihu Tang (Major Bupleurum Decoction) purges formless pathogens in Shaoyang (Lesser Yang); Chaihu Jianiaoxiao Tang (Bupleurum Plus Natrii Sulfas Decoction) purges formed pathogens in Shaoyang (Lesser Yang). Guizhi Jiashao Yao Tang (Cinnamon Twig Plus Peony Decoction) purges formless pathogens in Taiyin (Great Yin); Sanwu Baisan (Three-Ingredient White Powder) purges formed pathogens in Taiyin (Great Yin). Sini San (Bupleurum Powder for Reversal Cold) purges formless pathogens in Shaoyin (Lesser Yin) and Jueyin (Terminal Yin); Chengqi Tangs (Order the Qi Decoctions) purge formed pathogens in various meridians. There is a distinction in severity: mild purgatives use only Qi-level herbs; severe purgatives combine Blood-level herbs. Sour-bitter inducing discharge is mild purgation, so Shaoyao (Paeoniae Radix Alba) and Zhishi (Aurantii Fructus Immaturus) are mild; salty-bitter inducing discharge is severe purgation, so Da Huang (Rhei Radix et Rhizoma) and Mangxiao (Natrii Sulfas) are severe.

Zhongjing's use of "purge" does not refer exclusively to defecation. When giving Guizhi Tang (Cinnamon Twig Decoction) to attack the exterior, it refers to sweating; when the exterior is resolved and one may then attack, it refers to promoting urination; when heat belongs to the Zang organs and is attacked, it refers to clearing fire. Cold-dampness in the interior should not be purged via defecation; referring to promoting urination. Because there is heat, one should use a decoction to purge; referring to clearing fire.

Zhongjing's purgatives focus on decoctions, hence stating that physicians using pill-based purgation is incorrect. Examining Xiantiong Wan (Chest Trap Pill) and Didang Wan (Arriving at Blood Stasis Pill), they are still prepared with water, effectively restoring the power of decoctions. Taking approximately two ounces, including dregs, makes their potency stronger than decoctions or powders. One must understand that Zhongjing's prescriptions measured in Zhu, Liang, and Fen are not for exogenous diseases; pills the size of tung seeds, taken ten at a time, are not methods for treating exogenous diseases.

Zhongjing established prohibitions alongside his prescriptions to ensure patients benefit without suffering side effects. For example, when using exterior-releasing herbs, if sweating occurs after one dose, stop subsequent doses. If the pulse is floating-tight, with fever and no sweating, do not give Guizhi Tang (Cinnamon Twig Decoction); if the pulse is weak-thin, with sweating and aversion to wind, do not administer Da Qinglong Tang (Major Azure Dragon Decoction); if the pulse is floating with fever and no sweating, with unresolved exterior, do not give Baihu Tang (White Tiger Decoction); for all patients with blood loss or deficiency, do not use Gouti San (Melon Tip Powder); for patients with a history of loose stools, do not give Zhizi Chi Dao Tang (Gardenia and Fermented Soybean Decoction); for Yangming (Yang Brightness) disease with excessive sweating, do not give Zhuling Tang (Poria Decoction); if the exterior is unresolved and heat is not tidal, do not give Chengqi Tang (Order the Qi Decoction); for patients prone to vomiting, do not give Jianzhong Tang (Establish the Middle Decoction). These are all cautious measures by Zhongjing. Zhongjing's modifications hold deep meaning. For abdominal pain: add Shaoyao (Paeoniae Radix Alba) in Shaoyang (Lesser Yang), Fuzi (Aconiti Lateralis Radix Preparata) in Shaoyin (Lesser Yin), and Renshen (Ginseng Radix et Rhizoma) in Taiyin (Great Yin). For epigastric palpitations: add Guizhi (Cinnamomi Ramulus) in Shaoyin (Lesser Yin) and Fuling (Polyporus) in Shaoyang (Lesser Yang). For thirst: add Gualugen (Trichosanthis Radix) and Renshen (Ginseng Radix et Rhizoma) in Shaoyang (Lesser Yang), and Baizhu (Atractylodis Macrocephalae Rhizoma) in Taiyin (Great Yin). Modifications distinguish Yin-Yang and Exterior-Interior thus. Carefully studying Zhongjing's prescriptions reveals the wonder of symptom-based formulation; understanding his modification rules reveals the precision of his herb selection.

Xiao Qinglong Tang (Minor Azure Dragon Decoction) lists five possible symptoms, with five corresponding modification formulas. Xiao Chaihu Tang (Minor Bupleurum Decoction) lists seven possible symptoms, with seven corresponding modification formulas. Understand that Zhongjing has primary governing formulas, such as Mahuang Tang (Ephedra Decoction) and Guizhi Tang (Cinnamon Twig Decoction); he has formulas outside formulas, such as Guizhi Tang (Cinnamon Twig Decoction) plus Fuzi (Aconiti Lateralis Radix Preparata) or Dahuang (Rhei Radix et Rhizoma); he has formulas within formulas, such as the modification rules for Qinglong Tang (Azure Dragon Decoction) and Zhenwu Tang (True Warrior Decoction). Zhongjing's writing contains methods within methods, and formulas outside formulas. How can one be constrained by 397 methods and 113 prescriptions?

In ancient times, Qibo created the Seven Prescriptions to treat diseases. Zhongjing further explored the variability of diseases to exhaust their subtleties. Releasing the exterior and purging the interior are major methods for expelling pathogens, with formulas varying in size, such as Qinglong Tang (Azure Dragon Decoction), Chaihu Tang (Bupleurum Decoction), Xiantiong Tang (Chest Trap Decoction), and Chengqi Tang (Order the Qi Decoction). Since exterior-releasing formulas like Mahuang Tang (Ephedra Decoction) and Guizhi Tang (Cinnamon Twig Decoction) exist, if interior pathogens accompany exterior ones, treating only the exterior is incomplete. Interior pathogens may accompany cold or heat. Thus, Xiao Qinglong Tang (Minor Azure Dragon Decoction) treats exterior heat with interior cold, and Da Qinglong Tang (Major Azure Dragon Decoction) treats exterior cold with interior heat, resolving the interior within the exterior treatment, avoiding the sequential calculations required for transformed diseases. However, Da and Xiao Qinglong Tangs are variations of Mahuang and Guizhi Tangs, sufficient only for Ying-Wei exterior, not for Couli pathogens. Pathogens lingering in the Couli share the alternating chills and fever of the semi-exterior, but the semi-interior may involve deficiency or excess. Thus, Xiao Chaihu Tang (Minor Bupleurum Decoction) prevents semi-interior deficiency, and Da Chaihu Tang (Major Bupleurum Decoction) removes semi-interior excess, harmonizing the interior within the exterior treatment, avoiding the sequential tonification/purging debates of later scholars. Since Tiaowei Chengqi Tang (Regulate the Stomach Order the Qi Decoction) exists for purging the interior, if interior pathogens are in the Upper Jiao (Upper Burner), they may involve water or phlegm; if in the Middle Jiao (Middle Burner), stool may be initially hard then loose, or firmly dry. Tiaowei Chengqi Tang (Regulate the Stomach Order the Qi Decoction) cannot resolve these. Thus, Xiaoxiantiong Tang (Minor Chest Trap Decoction) clears phlegm in the chest/diaphragm; Daxiantiong Tang (Major Chest Trap Decoction) drains water in the chest/diaphragm; Xiaochengqi Tang (Minor Order the Qi Decoction) tests stomach gas; Dachengqi Tang (Major Order the Qi Decoction) attacks dry feces in the intestines. This ensures precision, expelling pathogens without damaging righteous Qi, avoiding neglect or excess. Commentary: Exterior-releasing and interior-purging formulas have varying speeds. Mahuang Tang (Ephedra Decoction) and Dachengqi Tang (Major Order the Qi Decoction) are urgent sweating and purging agents, while Guizhi Tang (Cinnamon Twig Decoction) is a slow exterior-releasing agent. Its methods show gradations within slow sweating. Xiaochengqi Tang (Minor Order the Qi Decoction) is a slow purgative; instructions say "give little to achieve slight relief," "slightly harmonize stomach Qi," and "do not give more if no gas passes." Tiaowei Chengqi Tang (Regulate the Stomach Order the Qi Decoction) is even slower; instructions say "take small amounts warm," and it omits Qi-moving herbs, adding Gancao (Glycyrrhizae Radix et Rhizoma). Thus, differences exist within slow purgation. Regarding odd/even methods, while various formulas are seen, there is the even combination of Mahuang-Guizhi Ge Ban Tang (Half-Mahalf-Guizhi Decoction) and the odd combination of Guizhi Er Mahuang Yi Tang (Two Parts Cinnamon Twig, One Part Ephedra Decoction), showing depth within odd/even. After taking Guizhi Tang (Cinnamon Twig Decoction), drinking hot porridge creates a compound formula. Further, taking one sheng of Xiao Chaihu Tang (Minor Bupleurum Decoction) plus Mangxiao (Natrii Sulfas) creates another compound, dividing sweating and purging within compounds. Bai San (White Powder) uses compound methods differently: if no diarrhea, drink a cup of hot porridge; if diarrhea persists, drink a cup of cold porridge. One cup of porridge contains both heat-dispersing and cold-tonifying methods.

Diseases involving deficient heat, mixed cold-heat, or areas unreachable by medicine may be treated by Zhongjing with acupuncture or moxibustion. Since later ages separated acupuncture and herbal medicine, with acupuncturists avoiding herbs and herbalists avoiding needles, few understand the complementary nature of needle and drug therapy. According to Qibo, treating Fengjue (Wind-Jue) involved simultaneous exterior-interior acupuncture and herbal decoctions. Thus, Zhongjing treated Taiyang (Greater Yang) wind-stroke; after taking Guizhi Tang (Cinnamon Twig Decoction), vexation反而 (instead/reversely)...