太阳居三阳之表，其病过经不解，不转属阳明，则转少阳矣。心烦喜呕，为柴胡证。然柴胡证或胸中烦而
不痛，或大便微结而不溏，
或腹中痛而不满。此则胸中痛，大便溏，腹微满，皆不是柴胡证。但以欲呕一证似柴胡，当深究其欲呕之故矣。
夫伤寒中风，有柴胡证，有半表证也，故呕而发热者主之。此病既不关少阳寒热往来、胁下痞硬之半表，见太阳
过经而来，一切皆属里证，必十日前吐下而误之坏病也。胸中痛者，必极吐可知；腹微满，便微溏，必误下可
知。是太阳转属阳明，而不属少阳矣。今胃气虽伤，而余邪未尽，故与调胃承气和之。不用枳、朴者，以胸中
痛、上焦伤，即呕多虽有阳明证，不可攻之谓也。若未经吐下，是病气分而不在胃。则呕不止而郁郁微烦者，
当属之大柴胡矣。
此阳明少阳疑似证。前条得坏病之虚，此条得坏病之实。
上论柴胡变证。
太阳病过经十余日，反二三下之，后四五日，柴胡证仍在者，先与小柴胡汤。呕不止，心下急，郁郁微烦者，
为未解也，与大柴胡汤下之则愈。
病从外来者，当先治外而后治其内。此屡经妄下，半月余而柴胡证仍在。因其人不虚，故枢机有主而不为
坏病。与小柴胡和之，表证虽除，内尚不解。以前此妄下之药，但去肠胃有形之物，而未泄胸膈气分之结热也。
急者满也，但满而不痛，即痞也。姜、夏以除呕，柴、芩以去烦，大枣和里，枳芍舒急。而曰下之则愈者，见大
柴胡为下剂，非和剂也。若与他药和下之，必有变证，意在言外。呕不止，属有形；若欲呕，属无形。
伤寒十余日，热结在里，复往来寒热者，与大柴胡汤。
里者对表而言，不是指胃。此热结气分，不属有形，故十余日复能往来寒热。若热结在胃，则蒸蒸发热，不
复知有寒矣。往来寒热，故倍生姜佐柴胡以解表；结热在里，故去参、甘之温补，加枳、芍以破结。
伤寒发热，汗出不解，心下痞硬，呕吐而下利者，大柴胡汤主之。
汗出不解，蒸蒸发热者，是调胃承气证。汗出解后，心下痞硬、下利者，是生姜泻心证。此心下痞硬，协热
而利，表里不解，似桂枝人参证。然彼在妄下后而不呕，则此未经下而呕，则呕而发热者，
小柴胡主之矣。然痞硬在心下而不在胁下，斯虚实补泻之所由分也。故去参、甘之甘温益气，而加枳、芍之酸
苦涌泄耳。
上论大柴胡证。
大柴胡汤∶
小柴胡汤去人参、甘草，加生姜（二两），芍药（三两），枳实（四枚）。余同小柴胡法。
按∶大柴胡是半表半里气分之下药，并不言大便。其心下急与心下痞硬，是胃口之病，而不在胃中；结热
在里，非结实在胃。且下利则地道已通，仲景不用大黄之意晓然。若以“下之”二字，妄加大黄，则十枣汤“攻
之”二字，如何味乎？
大小柴胡，俱是两解表里，而有主和主攻之异。和无定体，故有加减；攻有定局，故无去取之法也。
Taiyang (Sun Yang) resides on the exterior of the three Yang channels. If its disease persists beyond the transmission period without transferring to Yangming, it will transfer to Shaoyang. Mental restlessness and a propensity for vomiting are signs of Chaihu Syndrome. However, in Chaihu Syndrome, one may experience mental restlessness in the chest without pain, or slightly constipated stools without diarrhea, or abdominal pain without fullness. In this case, however, there is pain in the chest, loose stools, and slight abdominal fullness; none of these are indications for Chaihu Syndrome. Since only the symptom of "desire to vomit" resembles Chaihu Syndrome, one must deeply investigate the cause of this desire to vomit.
In Cold Damage or Wind Strike, if Chaihu Syndrome is present, it belongs to the Half-Exterior/Half-Interior syndrome. Therefore, for patients with vomiting and fever, [Chaihu Tang] is the primary treatment. This disease does not involve the Half-Exterior symptoms of Shaoyang, such as alternating chills and fever or hypochondriac stiffness and fullness. Instead, presenting as Taiyang disease persisting beyond its term, all symptoms belong to the Interior. This must be a *Huai Bing* (complicated disease caused by mismanagement) resulting from erroneous use of emetic or purgative therapies within the previous ten days. Pain in the chest indicates that excessive emesis was likely used; slight abdominal fullness and loose stools indicate that erroneous purgation was likely used. Thus, Taiyang has transferred to Yangming, not to Shaoyang. Although the Stomach Qi is now injured, residual pathogenic factors remain. Therefore, Tiaowei Chengqi Tang is given to harmonize. Zhi Shi (Immature Bitter Orange) and Hou Po (Magnolia Bark) are not used because, as stated in the text, "if there is much vomiting even with Yangming signs, one must not attack," implying that due to pain in the chest and injury to the Upper Jiao, purgation is contraindicated. If no emetic or purgative had been used previously, the pathogen would be in the Qi level rather than the Stomach organ. In such cases, persistent vomiting accompanied by mild depression and irritability would belong to Dahuang Huanglian Xiexin Tang or similar patterns, but specifically here, it points towards Dachaihu Tang.
This is a differential diagnosis between Yangming and Shaoyang diseases. The preceding clause discusses the deficiency aspect of *Huai Bing*, while this clause discusses the excess aspect. The above discusses the variations of Chaihu Syndrome.
If Taiyang disease persists for more than ten days after transmission, and is erroneously treated with purgatives two or three times, and after another four or five days, Chaihu Syndrome still remains, first administer Xiaochaihu Tang. If vomiting persists, there is urgency and tightness below the heart, and mild depression with irritability, the disease is unresolved; administer Dachaihu Tang to purge, and recovery will follow.
When pathogens come from outside, one should treat the exterior first and then the interior. Here, despite multiple erroneous purgations over more than half a month, Chaihu Syndrome remains. Because the patient's constitution is not deficient, the pivot mechanism has a master and does not become a *Huai Bing*. Administering Xiaochaihu Tang harmonizes the condition. Although the exterior signs are removed, the interior is still unresolved. This is because the previous erroneous purgatives only removed有形 (有形之物 - tangible/physical accumulation) in the intestines and stomach, but did not dissipate the heat constrained in the Qi level of the chest and diaphragm. "Urgency" refers to fullness; fullness without pain constitutes Pi (痞 - stuffiness/blockage). Shengjiang (Fresh Ginger) and Banxia (Pinellia Rhizome) remove vomiting; Chaihu (Bupleurum Root) and Huangqin (Scutellaria Root) remove irritability; Dazao (Jujube Fruit) harmonizes the interior; Zhishi (Immature Bitter Orange) and Shaoyao (Peony Root) relieve urgency. The phrase "purge to achieve cure" indicates that Dachaihu Tang is a purgative formula, not a harmonizing formula. If combined with other drugs for mild purgation, variable syndromes would inevitably arise; the intent lies beyond the words. Persistent vomiting belongs to tangible obstruction; desire to vomit belongs to intangible Qi dysfunction.
In Cold Damage lasting over ten days, if heat is constrained internally and there is also alternating chills and fever, administer Dachaihu Tang.
"Interior" here is relative to "Exterior" and does not refer specifically to the Stomach. This heat constraint is in the Qi level, not tangible matter, so alternating chills and fever can still occur after ten days. If heat were constrained in the Stomach, it would manifest as steaming fever, and one would no longer perceive chills. Due to alternating chills and fever, the dosage of Shengjiang is doubled to assist Chaihu in resolving the exterior; due to heat constraint in the interior, Ren Shen (Ginseng Root) and Gan Cao (Licorice Root) are removed to avoid warm tonification, and Zhishi (Immature Bitter Orange) and Shaoyao (Peony Root) are added to break up constraints.
In Cold Damage with fever, where sweating does not resolve the condition, accompanied by stuffiness and hardness below the heart, vomiting, and diarrhea, Dachaihu Tang is the primary treatment.
Sweating without resolution and steaming fever indicate Tiaowei Chengqi Tang syndrome. Resolution of fever after sweating, followed by stuffiness/hardness below the heart and diarrhea, indicates Shengjiang Xiexin Tang syndrome. Here, stuffiness/hardness below the heart with heat-collateralized diarrhea and unresolved exterior/interior resembles Guizhi Renshen Tang syndrome. However, that syndrome occurs after erroneous purgation without vomiting, whereas this case involves vomiting without prior purgation. If there were vomiting and fever, Xiaochaihu Tang would be indicated. However, the stuffiness/hardness is located below the heart, not in the hypochondrium, which distinguishes deficiency/excess and tonification/purgation. Therefore, Ren Shen (Ginseng Root) and Gan Cao (Licorice Root) are removed to avoid sweet-warm Qi tonification, and Zhishi (Immature Bitter Orange) and Shaoyao (Peony Root) are added for sour-bitter draining and purging effects. The above discusses Dachaihu Tang syndrome.
Dachaihu Tang:
Derived from Xiaochaihu Tang by removing Ren Shen (Ginseng Root) and Gan Cao (Licorice Root), adding Shengjiang (Fresh Ginger, 2 liang), Shaoyao (Peony Root, 3 liang), and Zhishi (Immature Bitter Orange, 4 pieces). The remaining preparation method follows Xiaochaihu Tang.
Note: Dachaihu Tang is a purgative acting on the Qi level of the Half-Exterior/Half-Interior; it does not mention bowel movements. "Urgency below the heart" and "stuffiness/hardness below the heart" are disorders of the stomach opening, not the Stomach organ itself; heat constraint in the interior is not solid accumulation in the Stomach. Furthermore, since diarrhea is present, the lower pathway is already open, making Zhang Zhongjing's intention to omit Da Huang (Rhubarb Root) clear. If one were to arbitrarily add Da Huang based on the word "purge," how would one interpret the word "attack" in Shizao Tang?
Both Dachaihu Tang and Xiaochaihu Tang resolve both exterior and interior, but one focuses on harmonizing and the other on attacking. Harmonization has no fixed form, hence modifications exist; attacking has a fixed pattern, hence there is no method of removal or selection.