The pulse is floating and tight. If purgation is mistakenly applied, the tightness reverses and enters the interior, resulting in Pi syndrome (epigastric fullness without hardness). Palpation reveals softness; this is merely Qi stagnation forming a Pi pattern.

This further elaborates on the cause of Pi formation. A floating and tight pulse characterizes Cold Damage disease, referred to as "disease originating from Yin." The reversal of tightness entering the interior indicates that cold pathogenic factors have sunk inward due to purgation, consistent with the mechanism where heat pathogens sink to form Jie Xiong (chest binding). However, Jie Xiong presents with hardness and pain in the epigastrium, whereas Pi presents with softness upon palpation, lacking both hardness and pain. This is because Yang pathogens sinking into the interior remain in the Stomach, binding with water and food residue to form Jie Xiong; Yin pathogens sinking into the interior remain outside the Stomach, binding with Qi and fluids to form Pi. Thus, Jie Xiong is an Excess pattern, characterized by hardness and pain upon palpation; Pi is a Deficiency pattern, characterized by natural softness upon palpation.

When there is epigastric fullness (Pi), softness upon palpation, and a floating pulse at the Guan position, Da Huang Huang Lian Xie Xin Tang (Rhubarb and Coptis Decoction for Draining the Epigastrium) is indicated.

Cheng Wuji stated: Hardness in the epigastrium with pain upon palpation and a deep Guan pulse indicates Excess Heat; epigastric fullness with softness upon palpation and a floating Guan pulse indicates Deficient Heat. Da Huang (Rhei Radix et Rhizoma) and Huang Lian (Coptidis Rhizoma) are used to guide out this Deficient Heat. Cheng's term "Deficient Heat" refers to heat not bound with dry feces, rather than Yin or Yang Deficiency. Generally, when heat pathogens enter the interior and bind with waste matter, it is Excess Heat; when they do not bind with waste matter, it is Deficient Heat. This formula uses Da Huang and Huang Lian but excludes Zhi Shi (Aurantii Fructus), Hou Po (Magnoliae Officinalis Cortex), and Mang Xiao (Natrii Sulfas) because its purpose is to drain heat, not to purge excess accumulation. Ma Fei Tang (Sesame-Bubble Boiling Water) refers to water boiled until small bubbles appear like sesame seeds; the herbs are soaked in this hot water to prevent the full extraction of medicinal potency.

Da Huang Huang Lian Xie Xin Tang Formula
Da Huang (2 liang) Huang Lian (1 liang)
Take the above two ingredients, soak them in 2 sheng of Ma Fei Tang. After a moment, strain off the dregs. Divide into two doses and take warm.

When there is epigastric fullness accompanied by aversion to cold and sweating, Fu Zi Xie Xin Tang (Aconite Decoction for Draining the Epigastrium) is indicated.

This extends the previous clause, stating that if there is epigastric fullness, softness upon palpation, and a floating Guan pulse, Da Huang Huang Lian Xie Xin Tang should be used to drain Deficient Heat in the epigastrium. If the patient additionally exhibits aversion to cold and sweating, indicating concurrent Yang Deficiency, Fu Zi (Aconiti Lateralis Radix Praeparata) must be added to restore exterior Yang Qi. This is a method of combining cold and hot properties, treating both pathogen and righteous Qi simultaneously.

Fu Zi Xie Xin Tang Formula
Da Huang (2 liang) Huang Lian (1 liang) Huang Qin (Scutellariae Radix, 1 liang) Fu Zi (1 piece, processed, skin removed, broken, decocted separately for juice)
Cut the above four ingredients. Soak three of them (Da Huang, Huang Lian, Huang Qin) in 2 sheng of Ma Fei Tang. After a moment, strain off the dregs, and add the Fu Zi juice. Divide into three doses and take warm.

Regarding this pattern, there is an excess of pathogenic heat but a deficiency of righteous Yang. If one treats the pathogen while neglecting the righteous Qi, aversion to cold will worsen; if one tonifies Yang while neglecting heat, epigastric fullness will increase. This formula administers cold, hot, tonifying, and purging agents simultaneously for mutual treatment, which is indeed a painstaking measure of necessity. However, without proper methods to control them, few would achieve efficacy without confusion. By soaking the cold-natured herbs in Ma Fei Tang and separately decocting Fu Zi for juice, then mixing them for administration, the cold and hot properties remain distinct, and raw versus cooked natures differ. Although administered together, their effects act independently. This is the profound application of the ancient sages.

After five or six days of Cold Damage, if vomiting and fever are present, Chai Hu Tang (Bupleurum Decoction) patterns are established. If other drugs are mistakenly used for purgation, and Chai Hu patterns persist, Chai Hu Tang should be re-administered. Although purgation has been performed, this is not considered a counter-indication (Ni).
There will likely be a sensation of steaming heat followed by chills, after which fever and sweating occur, leading to resolution. If the epigastrium is full, hard, and painful, this is Jie Xiong (Chest Binding), treated with Da Xian Xiong Tang (Major Blue-Green Pill for Draining the Chest). If it is merely full without pain, this is Pi (Epigastric Fullness); Chai Hu Tang is contraindicated, and Ban Xia Xie Xin Tang (Pinellia Decoction for Draining the Epigastrium) is appropriate.

Both Jie Xiong and Pi can result from mistaken purgation in Taiyang (Greater Yang) disorders, as well as Shaoyang (Lesser Yang) disorders. "Chai Hu Tang patterns established" implies that Shaoyang symptoms such as vomiting, fever, wiry pulse, and bitter taste are all present. Harmonization is indicated, but purgation was wrongly applied, constituting a counter-indication. If Chai Hu patterns persist, re-administering Chai Hu Tang for harmonization leads to recovery; despite prior purgation, this is not a counter-indication. Steaming heat and chills indicate internal righteous Qi rising to contend with the pathogen, followed by fever, sweating, and pathogen resolution. Without Chai Hu patterns, epigastric fullness with hardness and pain indicates Jie Xiong; fullness without pain indicates Pi. Neither is treatable by Chai Hu Tang. Jie Xiong requires Da Xian Xiong Tang; Pi requires Ban Xia Xie Xin Tang. Treatment varies according to the specific pattern.

Ban Xia Xie Xin Tang Formula
Huang Qin (3 liang) Ren Shen (Ginseng Radix, 3 liang) Gan Cao (Licorice Root, 3 liang) Huang Lian (1 liang) Ban Xia (Pinelliae Tuber, half sheng, washed) Gan Jiang (Zingiberis Rhizoma, 3 liang) Da Zao (Jujubae Fructus, 12 pieces)
Take the above seven ingredients, decoct in 10 dou of water to obtain 6 sheng. Strain, then decoct again to obtain 3 sheng. Take 1 sheng warm, three times daily.

Pi is defined as fullness without solidity. When external pathogens sink inward, diaphoresis (sweating) is contraindicated; since the fullness is not solid, purgation is also contraindicated. Therefore, only the acridity of Ban Xia and Gan Jiang can disperse the knot, and the bitterness of Huang Lian and Huang Qin can drain the fullness. While these actions are functions of the herbs, they rely fundamentally on the Stomach Qi. Ren Shen, Gan Cao, and Da Zao are used because purgation causes Middle Jiao Deficiency; they tonify Qi and assist the efficacy of the other herbs.

After Cold Damage resolves via sweating, if the Stomach becomes disharmonious, presenting with epigastric stiffness/fullness, dry belching with food odor, fluid retention under the costal region, borborygmus, and diarrhea, Sheng Jiang Xie Xin Tang (Fresh Ginger Decoction for Draining the Epigastrium) is indicated.

After resolution via sweating, Stomach disharmony prevents the circulation of True Qi and the digestion of food. This results in epigastric fullness and stiffness, and dry belching with food odor, as described in the *Jin Gui Yao Lue* (Essential Prescriptions of the Golden Cabinet): "Middle Jiao Qi is unharmonized, unable to digest grain, thus causing belching." Belching here refers to expelling food odor. Fluid retention under the costal region, borborygmus, and diarrhea indicate insufficient Earth virtue allowing Water pathogenic factors to cause harm. Thus, Xie Xin Tang is used to drain the epigastrium, and Sheng Jiang (Zingiberis Rhizoma Recens) is added to harmonize the Stomach.

Note: The previous clause pertains to Shaoyang disease and should not ideally be in the Taiyang chapter. This clause concerns post-sweat resolution and is not a counter-indication. Both are listed here to illustrate the various applications of Xie Xin Tang formulas.

Sheng Jiang Xie Xin Tang Formula
Sheng Jiang (4 liang, sliced) Ren Shen (3 liang) Ban Xia (half sheng, washed) Gan Cao (3 liang, honey-fried) Huang Qin (3 liang)
Da Zao (12 pieces, split) Huang Lian (1 liang) Gan Jiang (1 liang)
Take the above eight ingredients, decoct in 10 dou of water to obtain 6 sheng. Strain, then decoct again to obtain 3 sheng. Take 1 sheng warm, three times daily.

In Cold Damage or Wind Strike, if the physician mistakenly applies purgation, the patient may experience diarrhea dozens of times daily, undigested food, borborygmus, epigastric fullness/stiffness, dry vomiting, irritability, and restlessness. Seeing epigastric fullness, the physician might assume residual pathogen and purge again, worsening the fullness. This is not accumulated heat, but rather Stomach Deficiency with rebellious Qi ascending, causing hardness. Gan Cao Xie Xin Tang (Licorice Decoction for Draining the Epigastrium) is indicated.

"Cold Damage or Wind Strike" refers to Cheng Wuji's description. Pathogens are abundant at the exterior, yet purgation is wrongly applied, leading to diarrhea with undigested food, borborygmus, epigastric fullness/stiffness, dry vomiting, and irritability. This indicates exterior pathogens sinking into the Heart/Epigastrium and attacking upward and downward. Unless the Middle Qi is profoundly deficient, how could pathogens overflow to this extent? The physician mistook this for lingering accumulated heat and purged again, exacerbating the existing Deficiency. Deficiency prevents Qi transformation, causing further rebellious Qi and worsening fullness. Therefore, Xie Xin Tang is used to drain the epigastrium, and Gan Cao is added to tonify Middle Qi.

Gan Cao Xie Xin Tang Formula
Gan Cao (4 liang) Huang Qin (3 liang) Gan Jiang (3 liang) Huang Lian (1 liang) Ban Xia (half sheng, washed) Da Zao (12 pieces, split)
Take the above six ingredients, decoct in 10 dou of water to obtain 6 sheng. Strain, then decoct again to obtain 3 sheng. Take 1 sheng warm, three times daily.

Note: Although both Sheng Jiang Xie Xin Tang and Gan Cao Xie Xin Tang treat Pi, Sheng Jiang Xie Xin Tang targets Stomach disharmony, using Sheng Jiang to harmonize the Stomach. Gan Cao Xie Xin Tang targets persistent diarrhea and rebellious Qi; therefore, Ren Shen is omitted to avoid increasing Qi, and Gan Cao is used to calm the Middle.

After severe purgation followed by sweating in Cold Damage, if epigastric fullness and aversion to cold occur, the exterior pattern remains unresolved. One must not attack the Pi directly; the exterior must be resolved first. Only after the exterior is resolved can the Pi be treated.
For resolving the exterior, Gui Zhi Tang (Cinnamon Twig Decoction) is indicated. For treating the Pi, Da Huang Huang Lian Xie Xin Tang is indicated.

Severe purgation followed by sweating depletes righteous Qi and allows pathogens to enter, forming Pi. Typically, Xie Xin Tang would be used as above. However, if aversion to cold persists, although pathogens have entered the interior, the exterior pattern has not ceased. One must not directly attack the Pi. First, use Gui Zhi Tang to resolve the exterior, then use Da Huang Huang Lian Xie Xin Tang to treat the Pi. Otherwise, although the Pi might resolve, the exterior pathogens could re-enter the interior and cause complications. Moreover, the Pi might not resolve anyway.

Note: After mistaken purgation in Cold Damage, besides Jie Xiong and Pi, there are also Ao Nan (restlessness/oppression), fullness, and diarrhea patterns. Generally, if pathogens enter the interior but have not coalesced, and the location is high, it forms Ao Nan; if they have coalesced and are slightly lower, it forms Jie Xiong and Pi; if they are lowest and have not coalesced, it forms diarrhea. Jie Xiong and Pi are detailed above. These constitute seventeen clauses. The following eleven clauses detail various patterns of Ao Nan and diarrhea.