夫郁者，闭结凝滞瘀蓄抑遏之总名。《内经》五郁，以运气言也。丹溪六郁，以病因言
也。
以五郁言之，有诸家之释。然张氏之说为得其正，其说曰∶天地有五运之郁，人身有五脏之
应，郁则结聚不行，乃致当升不升，当降不降，当化不化，而郁作矣。故或郁于气，或郁于
血，或郁于表，或郁于里，或因郁而生病，或因病而生郁。郁而太过者，宜裁之抑之；郁而
不及者，宜培之助之。大抵诸病皆兼郁，为治有不同。所谓木郁达之者，达、畅达也。凡木
郁之病，风之属也，其脏应肝胆，其经在胁肋，其主在筋爪，其伤在脾胃，在血分，其性喜
调畅。故在表者，当疏其经；在里者，当疏其脏，但使气得通行，皆谓之达。诸家以吐为达
，又安足以尽之？火郁发之，发、发越也。凡火郁之病，为阳为热之属也。其脏应心，主小
肠三焦，其主在经络，其伤在阴分，火之所居，有结聚敛伏者，不宜蔽遏，当因其势而解之
散之升之扬之，如开其窗，揭其被，皆谓之发，非止于汗也。土郁夺之，夺、直取之也。凡
土郁之病，温湿之属也。其藏在脾胃，其主在肌肉四肢，其伤在胸腹，土畏壅滞。凡滞在上
者，夺其上，吐之可也；病在中者，夺其中，伐之可也；病在下者，夺其下，泻之可也。凡
此皆谓之夺，非止于下也。金郁泄之者，泄、疏利也。凡金郁之病，为敛为闭，为燥为塞之
属也，其藏应肺与大肠，其主在皮毛声息，其伤在气分，或解其表，或破其气，或通其便，
故在表在里，在上在下，皆可谓之泄也。水郁折之者，折、调制也。凡水郁之病，为寒为水
之属也，水之本在肾，水之标在肺，其伤在阳分，其反克在脾胃，水性喜流，宜防泛滥，折
之之法，如养气可以化水，治在肺也；实土可以制水，治在脾也，壮火可以胜水，治在命门
也；自强可以帅水，治在肾也；分利可以泄水，治在膀胱也。凡此皆谓之折，岂独抑之而已
哉。郁有五，法亦有五，郁去则气调矣。又以六郁言之，如气郁者，必胸腹满痛，其脉沉涩
；湿郁者，身体重着，或关节疼痛，遇阴寒即发，其脉沉缓；痰郁者，动则喘息，起卧怠惰
，其脉沉滑；血郁者，四肢无力，能食便红，其脉沉芤；食郁者，嗳酸恶食，痞块腹胀，其
脉气口沉紧∶热郁者，瞀闷口干，小便淋赤，其脉沉数，六郁不言风寒者，盖风寒郁则为热
故也。然丹溪又云∶气郁而湿滞。湿滞而成热，热郁而生痰，痰滞而血不行，血滞而食不消
化，是郁虽有六，又皆相因为病者也。夫治六郁者，以越鞠为丸为主方，固为尽善，但郁者
至久，元气未有不伤，克伐屡投，随散而随郁者，比比然也。于此当顾虑根本，权其重轻，
或攻补兼施，使邪衰而正胜，或专行于补益，俾养正以除邪。然郁在气血者，当以有形之药
，
分气血以疗之，医者之责也。若郁在情志者，即当以情志解散，此无形之气药，病者所自具
也。知乎此而立五六之治，思过半矣。
The term "Yu" (Stagnation) is a general name for closure, coagulation, stasis, accumulation, suppression, and obstruction. The "Five Yu" in the *Neijing* (Classic of Internal Medicine) refers to stagnation from the perspective of Five Movements and Six Qi (Wu Yun Liu Qi). The "Six Yu" proposed by Danxi (Zhu Zhenheng) refers to stagnation from the perspective of etiology.
Regarding the Five Yu, various schools have provided interpretations. However, the theory of Zhang (Zhang Zhicong) is considered the most orthodox. He stated: There are stagnations of the Five Movements in heaven and earth, which correspond to the five zang organs in the human body. When stagnation occurs, qi and blood gather and fail to circulate, leading to situations where what should ascend does not ascend, what should descend does not descend, and what should transform does not transform, thus giving rise to Yu. Therefore, stagnation may occur in qi, or in blood; it may be in the exterior, or in the interior; one may become ill due to stagnation, or stagnation may arise due to illness. For excessive stagnation, one should restrain and suppress it; for deficient stagnation, one should tonify and assist it. Generally, all diseases involve some degree of stagnation, but treatments vary.
The phrase "Wood Yu, soothe it" (Mu Yu Da Zhi): "Da" means to smooth and unblock. Diseases of Wood Yu belong to the category of Wind. The corresponding zang organs are the Liver and Gallbladder; the meridians traverse the hypochondrium; the external manifestation relates to tendons and nails; the damage affects the Spleen and Stomach and the Blood level; its nature favors free flow and smoothness. Therefore, if in the exterior, one should unblock the meridians; if in the interior, one should regulate the zang organs. As long as the qi mechanism is allowed to flow freely, it is called "Da". Some schools interpret "Da" solely as emesis, which is insufficient to capture its full meaning.
The phrase "Fire Yu, vent it" (Huo Yu Fa Zhi): "Fa" means to vent and disperse. Diseases of Fire Yu belong to the category of Yang and Heat. The corresponding zang organ is the Heart; it governs the Small Intestine and Sanjiao (Triple Burner); the external manifestation relates to the meridians; the damage involves the Yin level. Where fire resides, there may be aggregation, condensation, or concealment. It should not be suppressed or blocked; rather, one should follow the pathogenic trend to resolve, scatter, elevate, and扬 (raise/spread) it, like opening a window or lifting a blanket. This is called "Fa", which is not limited to diaphoresis (sweating).
The phrase "Earth Yu, seize/directly take it" (Tu Yu Duo Zhi): "Duo" means to directly remove or attack. Diseases of Earth Yu belong to the category of Warmth and Dampness. The zang organs are the Spleen and Stomach; the external manifestation relates to muscles and four limbs; the damage affects the chest and abdomen; Earth fears obstruction. If stagnation is in the upper part, attacking the upper part via emesis is appropriate; if in the middle part, attacking the middle part via purgation/attack is appropriate; if in the lower part, attacking the lower part via purgation/laxative therapy is feasible. All these are called "Duo", not limited to downward purgation.
The phrase "Metal Yu, drain it" (Jin Yu Xie Zhi): "Xie" means to dredge and facilitate drainage. Diseases of Metal Yu belong to the categories of Contraction, Closure, Dryness, and Obstruction. The corresponding zang organs are the Lung and Large Intestine; the external manifestation relates to skin/hair and respiration/voice; the damage affects the Qi level. One may release the exterior, break qi stagnation, or unblock bowels. Thus, whether in the exterior or interior, upper or lower, it can be called "Xie".
The phrase "Water Yu, modulate/restrain it" (Shui Yu Zhe Zhi): "Zhe" means to modulate or control. Diseases of Water Yu belong to the categories of Cold and Water. The root of water is in the Kidney; the branch is in the Lung; the damage affects the Yang level; counter-acting relationships involve the Spleen and Stomach. Water naturally flows and tends to flood; thus, modulation is needed. Methods include: nourishing Lung Qi to transform water (treating the Lung); strengthening Earth to control Water (treating the Spleen); boosting Mingmen Fire to overcome Water (treating the Mingmen); strengthening Kidney Qi to command Water (treating the Kidney); and promoting diuresis to drain Water (treating the Bladder). All these are called "Zhe", not merely suppression.
There are five types of Yu and five corresponding methods. Once Yu is resolved, qi becomes harmonized.
Regarding the Six Yu:
Qi Yu (Qi Stagnation) manifests as chest and abdominal fullness and pain, with a deep and choppy pulse.
Shi Yu (Dampness Stagnation) manifests as heavy body sensation or joint pain, worsening in cold/yin conditions, with a deep and slow pulse.
Tan Yu (Phlegm Stagnation) manifests as panting upon movement, lethargy in rising and lying down, with a deep and slippery pulse.
Xue Yu (Blood Stagnation) manifests as weakness in the four limbs, ability to eat but bloody stools, with a deep and hollow pulse.
Shi Yu (Food Stagnation) manifests as sour belching, aversion to food, epigastric distension and abdominal bloating, with a deep and tight pulse at the Qi Kou position.
Re Yu (Heat Stagnation) manifests as dizziness, stuffiness, dry mouth, and scanty red urine, with a deep and rapid pulse.
The Six Yu do not explicitly mention Wind-Cold because Wind-Cold, when stagnant, transforms into Heat. However, Zhu Danxi also stated: Qi stagnation leads to Dampness obstruction; Dampness obstruction generates Heat stagnation; Heat stagnation produces Phlegm stagnation; Phlegm stagnation impedes Blood circulation; Blood stagnation prevents Food digestion. Thus, although there are six types of Yu, they cause disease through mutual causality.
To treat the Six Yu, Yueju Wan (Cross-Junction Pill) is the principal formula, which is indeed excellent. However, prolonged Yu inevitably damages Yuan Qi (Primal Qi). Frequent use of draining/attacking herbs often results in the pathogen dispersing only to re-aggregate immediately. In such cases, one must protect the root and weigh the severity. One may combine attacking and tonifying methods to reduce pathogenic factors while strengthening healthy qi, or focus solely on tonification to eliminate pathogens by nurturing healthy qi.
For Yu in Qi and Blood, physicians must use tangible substances (herbs/minerals) to differentiate and treat Qi and Blood. For Yu in emotions/shen, one should use emotional therapy to dissolve it, utilizing intangible qi-based approaches inherent to the patient's mind. Understanding these principles allows one to establish treatments for the Five and Six Yu, achieving more than half of the therapeutic wisdom.