茯苓结于土中，久而不变，宜其得阴气多，与猪苓埒矣。然枫擅召雨之能，松挺不雕之
概；一毗于阴，一毗于阳。毗于阳者，能耗阴不能起阴，不能起阴即不能止渴。故五苓散治
汗出而渴，不渴则主以茯苓甘草汤；栝蒌瞿麦汤治渴，有茯苓不能无栝蒌；小柴胡汤渴加人
参，小青龙汤渴加栝蒌，皆独不加茯苓，此可征茯苓之非渴药。能起阴以止渴者，莫如葛根
栝蒌，以葛根栝蒌起阴而不利小便也。起阴而兼利小便，则止渴之力必减，故猪苓泽泻次之，
茯苓又次之。然五苓散猪苓汤偏以之治渴，更非葛根栝蒌所能代者何哉？盖其渴非他，脉浮
发热饮水而小便不利耳。不去其病，起阴奚济。茯苓与猪苓泽泻泄水，则小便利。茯苓猪苓
与桂枝滑石达表，则表邪解。去其蔽阴灼阴而阴自升，阴自升者渴亦止，此茯苓之于渴，所
以得厕名其间也。
虽然，其中又甚有故不得不辨者焉。二苓泽泻之治渴，是治饮水而小便不利之渴。以其
水为 潴之水，不受胃变则呕，格其肾阴则渴，故得以泄水利小便而愈。若是痰饮，胃亦赖
之以养；其浓浓者，且无走小便之理。将毋水能致渴，饮不能致渴耶！？而仲圣谓∶呕家本
渴反不渴者，心下有支饮；又谓∶胸中有留饮，其人短气而渴。二说相反，曷故？夫饮而曰
支，谓其如支流不正出也。不正出则肾阴犹得以上潮，故不渴。留饮是正留于胸中，气焉得
不短而渴焉得不作，是则痰与饮宜分者也。水与饮有分有不分者也。以渴不渴定茯苓与猪泽
之去取可矣。
抑又思之，仲圣用此三物之证，多渴与呕兼，岂非治渴而亦治呕。不知呕吐之专药为半
夏生姜，犹葛根栝蒌为消渴之专药。仲圣之以茯甘五味姜辛汤治咳满也，曰呕者复纳半夏。
既有茯苓又纳半夏，以茯苓不治呕也，不纳猪泽不治呕也。乃呕吐篇之猪苓散，明明治呕吐
思水。茯苓泽泻汤，明明治胃反吐而渴欲饮水。今必曰不治呕，其谁信之。然必曰治呕与小
半夏汤等，此何以多思水饮水之证，独是泄水以止渴者，其义易晓。泄水以止呕，则呕已自
去其水，何待药为。是则仲圣之言为甚可味也。猪苓散思水者三字，是对上后思水而言。此
思水为先思水，先思水而后呕吐，所谓先渴却呕者为水停心下也。水停心下者，愈渴亦愈饮，
呕
胃反者，胃虚且寒，不至有渴。今渴欲饮水，是阴中有阳之证。故于吐下加一而字以折醒之
。与他胃反不同，与他呕吐亦不同。姜桂甘术，所以温胃而止吐。茯苓泽泻，所以泄水而止
渴。证既兼见，药亦分理。有生姜无半夏者，渴忌半夏也。无猪苓者，无表证者也。泄水而
兼能止渴者，以泽泻为优，故入泽泻。至茯苓协泽泻泄水，协生姜平逆，协桂枝化气，协甘
草白术补中，为益良多，故以标方名冠首。以茯苓与猪泽较，虽同不治呕，而以茯苓为犹有
参赞之功。何则？甘先入脾，淡主养胃，茯苓甘淡，非猪泽可比，是其于呕也，不用剿而用
抚者也。
外此茯苓以泄水奏绩者，又于仲圣方得三事焉∶曰眩，曰悸，曰咳。必别其近似而真始
出，则与呕渴无二也。眩有肺痿上虚而眩，失精下损而眩，谷疸因食而眩，茯苓讵可漫施。
心下有支饮，其人苦冒眩，茯苓宜可用矣。不知泽泻汤无渴而用泽泻，以其于冒眩有专长也。
且使辅以茯苓，则泽泻方欲至极上治冒，而茯苓偏从而抑之，全功必堕。白术则蠲饮而守中，
足为泽泻策应，故宁退茯苓而进白术。然则，冒与非冒何别乎？盖冒者，上之阳为水饮所格
而不得入于阴，则淫于上如复冒，是眩在阳盛。以泽泻泄其水而济以阴，眩乃得息。若水饮
上凌、而上之阳不能与阴争，则阴与水相比为患而眩亦生，是眩在阴盛。惟茯苓禀阳和之性，
擅化气之长，水遇之而自却，阳得之而即伸。仲圣似此治眩之方不一，可不烦枚举。
水停心下而眩者，亦水停心下而悸。眩在外，悸在内，惟派别而源同，故眩定者悸亦定。
心下悸者水侵其心，脐下悸者水发自肾，似不能悉主以茯苓矣。然上中下之水，应皆从小便
出者，舍茯苓其奚属。且始而脐下悸者，后必心下亦悸，所谓水在肾心下悸也。其悸非茯苓
得治者，如小建中汤、桂枝甘草汤、炙甘草汤，非温养中气，补益心阳不可。茯苓淡渗，适
伤其正，故摈之也。
咳之因亦致多矣，茯苓所司为痰饮之咳。然有痰饮而不宜者∶半夏麻黄汤，有痰饮而悸，
以麻黄发心阳而泄之于表，徐忠可谓之老痰，老痰非渗得去。甘遂半夏汤，有留饮而利，以
甘遂甘草加白芍，就其利而下之，必欲使走小便则谬。此外有痰饮而宜辛散、宜苦降者无论
矣。夫咳者肺病，茯苓下渗，则肺邪不解，故咳证用之颇鲜。惟咳而冲气挟痰饮而上，胸满
由痰饮而得者，以茯苓下之泄之，厥效甚捷。然则茯苓非能治咳，治痰饮耳；非能治痰，实
治饮耳。苓桂术甘汤治痰饮如神，而其推茯苓为君也，在使微饮从小便去也，痰饮之有需于
茯苓可知矣。
抑其治饮治水，能使上中下统泄之于小便者有故。茯苓甘淡，为胃之正药。色白而纯，
则兼入肺。肺主皮毛而太阳为之应，故又入太阳。淡渗则又从皮毛而入太阳之府，肺胃职司
下降，膀胱气化则出，其利小便，盖有高屋建瓴之势焉。仲圣于小便不利而必曰加茯苓者，
职是故也。
夫利小便者，仲圣之明文，实本经之遗训，断不必以止消渴滋学人之惑。顾谓利小便足
尽其长乎，而不然也。试更即仲圣方核之，肾气丸主小便不利、并消渴、小便反多，盖小便
不利者，肾中阴气之壅也，以茯苓与桂附消其阴，则由壅得通；小便反多者，肾中阳气之弱
也，以茯苓与桂附扶其阳，则转弱为强。且用以祛表湿，如防己茯苓汤；用以解咽窒，如半
夏浓朴汤；用以开胸痹，如茯苓杏仁甘草汤；用以下症痼，如桂枝茯苓丸；用于补剂，如薯
蓣丸；用于风剂，如侯氏黑散。盖惟茯苓以甘淡之味，温和之性，能于气中消水，水中化气，
随他物而膺繁剧者，胥不出乎此旨。若非制剂得宜，则茯苓之真不见，而亦未必无害矣。
茯苓生长在土壤中，经过很长时间也不改变性质，这说明它获得的阴气很多，与猪苓相当。然而，枫树擅长招致雨水，松树具有挺拔不凋的品格；一个偏重于阴，一个偏重于阳。偏重于阳的药物，只能耗伤阴液而不能生起阴液，不能生起阴液也就不能止渴。所以五苓散治疗出汗后口渴，如果不渴则主要用茯苓甘草汤；栝蒌瞿麦汤治疗口渴，有茯苓但不能没有栝蒌；小柴胡汤在出现口渴时加人参，小青龙汤在出现口渴时加栝蒌，都唯独不加茯苓，这可以证明茯苓不是治疗口渴的药。能够生起阴液以止渴的，莫过于葛根和栝蒌，因为葛根和栝蒌能生起阴液而不通利小便。既能生起阴液又兼通利小便的，那么止渴的力量必然减弱，所以猪苓、泽泻排在后面，茯苓又排在它们后面。但是五苓散和猪苓汤偏偏用它来治疗口渴，这难道是葛根、栝蒌所能替代的吗？大概这种口渴并非其他原因，而是脉浮、发热、想喝水但小便不通利罢了。不去除导致疾病的因素，生起阴液有什么帮助呢？茯苓配合猪苓、泽泻泄去水邪，小便就通利了。茯苓、猪苓配合桂枝、滑石通达表邪，表邪就解除了。去除了遮蔽阴气和灼伤阴气的因素，阴液自然上升，阴液自然上升则口渴也停止，这就是茯苓在治疗口渴方面，之所以能名列其中的原因。
虽然如此，其中又有非常关键不得不辨明的地方。二苓（茯苓、猪苓）和泽泻治疗口渴，是治疗因饮水过多且小便不利引起的口渴。因为这些水是停滞的水，胃无法将其转化为津液就会呕吐，阻碍肾阴上承就会口渴，所以可以通过泄水利小便而痊愈。如果是痰饮，胃也依赖它来滋养；那些浓稠的痰饮，本来就没有从小便排出的道理。难道水能导致口渴，而饮不能导致口渴吗？！然而张仲景说：经常呕吐的人本来应该口渴，反而不渴的，是因为心下有支饮；又说：胸中有留饮，其人会短气并且口渴。这两种说法相反，是什么原因呢？“饮”称为“支”，是说它像支流一样不正出。不正出则肾阴还能够向上潮润，所以不渴。“留饮”是正停留于胸中，气机怎么能不短促，口渴怎么能不发生，这就是痰与饮应当区分的原因。水与饮是有分有不分的关系。根据是否口渴来决定使用茯苓还是猪苓、泽泻就可以了。
再进一步思考，张仲景使用这三味药（茯苓、猪苓、泽泻）的证候，多是口渴与呕吐并见，这难道不是既治口渴又治呕吐吗？不知道专门治疗呕吐的药物是半夏和生姜，就像葛根和栝蒌是专门治疗消渴的药物一样。张仲景用茯甘五味姜辛汤治疗咳嗽胀满时说，如果有呕吐再加半夏。既然已经有茯苓又加入半夏，是因为茯苓不治呕吐；不加猪苓、泽泻也是因为它们不治呕吐。但是在《呕吐哕下利病脉证治》篇中的猪苓散，明明治疗呕吐思水；茯苓泽泻汤，明明治疗胃反吐而渴欲饮水。现在一定说不治呕吐，谁会相信呢？然而如果说是治疗呕吐与小半夏汤等方剂相同，这里为什么多有思水、饮水的证候？唯独是泄水以止渴的道理容易明白。如果是泄水以止呕，那么呕吐已经随着水的去除而自行消失，何必等待药物呢？所以张仲景的话是很值得玩味的。“猪苓散”中“思水者”这三个字，是针对上文“后思水”而言的。这里的“思水”是先思水，先思水而后呕吐，所谓“先渴却呕者为水停心下”。水停在心下，越渴就越喝水；胃反者，胃虚且寒，不至于有口渴。现在渴欲饮水，这是阴中有阳的证候。所以在吐下之后加一个“而”字以提醒读者。这与其他的胃反不同，与其他呕吐也不同。干姜、肉桂、甘草、白术，是用来温胃止吐的；茯苓、泽泻，是用来泄水止渴的。证候既然兼见，药物也分别调理。有生姜无半夏，是因为口渴忌用半夏；无猪苓，是因为没有表证。泄水兼能止渴的，以泽泻为优，所以加入泽泻。至于茯苓协助泽泻泄水，协助生姜平逆，协助桂枝化气，协助甘草、白术补中，益处良多，所以将茯苓列在方名之首。拿茯苓与猪苓、泽泻比较，虽然都不治呕吐，但茯苓还有参赞之功。为什么呢？甘味先入脾，淡味主养胃，茯苓味甘淡，不是猪苓、泽泻可比的，这是它对呕吐不用攻剿而用安抚的方法。
除此之外，茯苓通过泄水取得疗效的，又在张仲景的方子中得到三件事：曰眩（头晕），曰悸（心悸），曰咳（咳嗽）。必须辨别近似症状才能显露真义，这就与呕吐、口渴没有两样了。眩晕有肺痿上虚导致的眩晕，失精下损导致的眩晕，谷疸因饮食导致的眩晕，茯苓岂可随意施用。心下有支饮，其人苦于冒眩（头目昏沉如物蒙盖），茯苓才可用。不知道泽泻汤没有口渴却用泽泻，是因为泽泻对冒眩有专长。而且如果辅以茯苓，则泽泻正要极力向上治疗冒眩，而茯苓偏于向下抑制它，全功必败。白术则祛除饮邪而守中焦，足以作为泽泻的策应，所以宁愿退下茯苓而进用白术。那么，冒眩与非冒眩有什么区别呢？大概“冒”是指上部的阳气被水饮阻隔而不能进入下部阴分，于是淫溢于上部如同复冒，这是眩晕属于阳盛。用泽泻泄去水邪并济以阴液，眩晕才能平息。如果水饮上凌，而上部阳气不能与阴争，则阴与水相合为患而生眩晕，这是眩晕属于阴盛。只有茯苓禀受阳和之性，擅长化气之长，水遇到它就退却，阳气得到它就伸展。张仲景类似治疗眩晕的方子不少，可以不烦琐地一一列举。
水停心下而眩晕的，也是水停心下而心悸。眩晕在外，心悸在内，只是派别不同而源头相同，所以眩晕定住则心悸也定住。心下悸是水侵犯心脏，脐下悸是水发自肾脏，似乎不能全部由茯苓主治。然而上中下三焦的水，都应该从小便排出，除了茯苓还能归属谁呢？况且起初是脐下悸，后来必定心下也悸，所谓水在肾则心下悸。那种不是茯苓能治疗的悸动，如小建中汤、桂枝甘草汤、炙甘草汤，非温养中气、补益心阳不可。茯苓淡渗，正好损伤正气，所以摒弃不用。
咳嗽的原因也很多，茯苓所主管的是痰饮引起的咳嗽。然而有痰饮却不适宜用茯苓的情况：半夏麻黄汤，有痰饮且伴有心悸，用麻黄发越心阳而从表泄出，徐忠可称之为老痰，老痰不是渗利可以去掉的。甘遂半夏汤，有留饮且有利下，用甘遂、甘草加白芍，顺着其利下的趋势而下之，如果一定要让它走小便就错了。此外有痰饮而宜用辛散、宜用苦降的就不必说了。咳嗽是肺的病，茯苓下行渗利，则肺邪不解，所以咳嗽证候中使用茯苓很少。只有咳嗽且冲气挟带痰饮上逆，胸满是因痰饮引起的，用茯苓下行泄之，效果非常迅速。那么，茯苓不是能治咳嗽，而是治痰饮罢了；不是能治痰，实在是治饮罢了。苓桂术甘汤治疗痰饮如神，而推崇茯苓为君药，在于使微饮从小便排出，可见痰饮需要用到茯苓。
再说它治疗饮邪和水邪，能使上中下三焦统统一从膀胱排出，是有原因的。茯苓味甘淡，是胃的正药。颜色洁白纯正，则兼入肺经。肺主皮毛而太阳经与之相应，所以又入太阳经。淡渗则又从皮毛而入太阳之腑，肺胃职司下降，膀胱气化则尿液排出，它的利小便作用，大概有高屋建瓴之势。张仲景在小便不利时必定说加茯苓，就是这个缘故。
利小便，是张仲景的明文规定，实际上是本经的遗训，断不必认为它能止消渴而滋扰学人的疑惑。如果说利小便就能穷尽它的长处吗，却不是这样。试更依据张仲景的方子核实，肾气丸主治小便不利，并治消渴、小便反多。大概小便不利，是肾中阴气壅滞，用茯苓配合桂枝、附子消除阴壅，则由壅得通；小便反多，是肾中阳气虚弱，用茯苓配合桂枝、附子扶助阳气，则转弱为强。并且用来祛除表湿，如防己茯苓汤；用来解除咽喉窒塞，如半夏厚朴汤；用来开通胸痹，如茯苓杏仁甘草汤；用来攻下症痼，如桂枝茯苓丸；用于补剂，如薯蓣丸；用于风剂，如侯氏黑散。大概只有茯苓凭借甘淡的味道，温和的性质，能在气中消水，在水中化气，跟随其他药物承担繁重任务，都不超出这个宗旨。如果不是制剂得当，则茯苓的真效不见，也未必没有害处。
Fuling (Poria) forms in the soil and remains unchanged for a long time, which indicates that it absorbs a significant amount of Yin Qi (Yin Energy), comparable to Zhuling (Polyporus). However, the maple tree has the ability to attract rain, while the pine tree stands tall without withering; one leans towards Yin, and the other towards Yang. Substances leaning towards Yang can consume Yin but cannot generate it; if they cannot generate Yin, they cannot relieve thirst. Therefore, Wuling San (Five-Ingredient Powder with Poria) is used for thirst following sweating; if there is no thirst, Fuling Gancao Tang (Poria and Licorice Decoction) is primarily used. Gualou Qumai Tang (Trichosanthes Root and Rhizoma Phlomi Decoction) treats thirst, where Fuling is present but Gualou (Trichosanthes Root) is indispensable. In Xiaochaihu Tang (Minor Bupleurum Decoction), when thirst occurs, Renshen (Ginseng) is added; in Xiaoqinglong Tang (Minor Green Dragon Decoction), when thirst occurs, Gualou is added. In neither case is Fuling added alone, which demonstrates that Fuling is not a herb for treating thirst. The herbs capable of generating Yin to relieve thirst are none other than Gegen (Kudzu Root) and Gualou. Since Gegen and Gualou generate Yin without promoting urination, their efficacy in relieving thirst is preserved. Herbs that generate Yin while also promoting urination, such as Zhuling and Zexie (Alisma), have reduced efficacy in relieving thirst, placing them after Gegen and Gualou, with Fuling ranking even lower. However, Wuling San and Zhuling Tang (Polyporus Decoction) specifically use these herbs to treat thirst. Why is this not replaceable by Gegen and Gualou? It is because this thirst is not due to other causes, but rather presents with floating pulse, fever, desire to drink water, and difficulty in urination. If the pathogenic factor is not removed, how can generating Yin help? When Fuling, combined with Zhuling and Zexie, drains water, urination becomes smooth. When Fuling and Zhuling, combined with Guizhi (Cinnamon Twig) and Huashi (Talc), release exterior pathogens, the exterior syndrome resolves. By removing the factors that obstruct and scorch Yin, Yin naturally rises. As Yin rises, thirst stops. This is why Fuling earns its place among herbs for treating thirst.
Nevertheless, there are crucial distinctions that must be clarified. The use of Er Ling (Fuling and Zhuling) and Zexie to treat thirst addresses thirst caused by excessive water intake coupled with impaired urination. Because this stagnant water cannot be transformed by the Stomach into fluids, it leads to vomiting; if it blocks Kidney Yin from ascending, it causes thirst. Thus, draining water and promoting urination cures it. However, if it is Phlegm-Fluids (Tan-Yin), the Stomach relies on it for nourishment; thick Phlegm-Fluids do not naturally exit via urination. Does this mean water causes thirst, but drinking fluids does not?! Yet Zhang Zhongjing stated: "Those who frequently vomit should normally feel thirsty; if they do not feel thirsty, it is due to Zhi Yin (branching fluid retention) under the heart." He also said: "When Liu Yin (retained fluid) is in the chest, the person suffers from shortness of breath and thirst." These two statements seem contradictory. What is the reason? "Zhi" implies branching or deviating flow. If the flow is not direct, Kidney Yin can still ascend to moisten, so there is no thirst. "Liu Yin" refers to fluid retained directly in the chest; thus, Qi movement is hindered (shortness of breath) and thirst arises. This distinguishes Tan (Phlegm) from Yin (Fluids). Water and Yin have both distinct and overlapping aspects. One can decide whether to use Fuling or Zhuling/Zexie based on the presence or absence of thirst.
Furthermore, considering Zhang Zhongjing's use of these three herbs (Fuling, Zhuling, Zexie), the syndromes often involve both thirst and vomiting. Does this imply they treat both? It is unknown whether Banxia (Pinellia) and Shengjiang (Fresh Ginger) are specific remedies for vomiting, just as Gegen and Gualou are specific for Xiao Ke (Wasting-Thirst). In Fugan Wuwei Jiangxin Tang (Poria, Licorice, Schisandra, Ginger, and Asarum Decoction) for cough and fullness, Zhang adds Banxia if vomiting is present. Since Fuling is already included, adding Banxia suggests Fuling does not treat vomiting; similarly, omitting Zhuling and Zexie suggests they do not treat vomiting either. However, in the chapter on Vomiting, Zhuling San (Polyporus Powder) clearly treats vomiting with desire for water, and Fuling Zexie Tang (Poria and Alisma Decoction) clearly treats gastric reversal vomiting with desire to drink water. To claim they do not treat vomiting would be unbelievable. But if they were equivalent to Xiaobanxia Tang (Minor Pinellia Decoction) for vomiting, why are there cases emphasizing desire for and drinking of water? The principle of draining water to stop thirst is clear. If draining water stopped vomiting, the vomiting would cease once the water was gone, without needing drugs. Thus, Zhang's words are profound. The phrase "desire for water" in Zhuling San refers to the "post-vomiting desire for water" mentioned earlier. Here, "desire for water" precedes vomiting. "Thirst followed by vomiting indicates water retention under the heart." When water retains under the heart, increased thirst leads to increased drinking. Gastric reversal involves Stomach deficiency and cold, which typically does not cause thirst. Current thirst with desire to drink indicates a syndrome of Yang within Yin. Hence, the conjunction "er" (and/then) is added to highlight this distinction from other gastric reversals or vomiting types. Jiang (Ginger), Rougui (Cinnamon Bark), Gancao (Licorice), and Baizhu (Atractylodes Macrocephala) warm the Stomach and stop vomiting. Fuling and Zexie drain water and stop thirst. Since symptoms overlap, treatments are differentiated. The presence of Shengjiang without Banxia is because Banxia is contraindicated in thirst. The absence of Zhuling indicates no exterior syndrome. Zexie is superior for draining water and stopping thirst, hence its inclusion. Fuling assists Zexie in draining water, Shengjiang in calming rebellion, Guizhi in transforming Qi, and Gancao/Baizhu in tonifying the Middle. Its benefits are manifold, justifying its position as the chief herb. Compared to Zhuling and Zexie, although none treat vomiting directly, Fuling offers supportive assistance. Why? Sweet flavor enters the Spleen first; bland flavor nourishes the Stomach. Fuling is sweet and bland, unlike Zhuling and Zexie. Thus, regarding vomiting, it uses a soothing approach rather than an aggressive one.
Beyond this, Fuling achieves results through draining water in three other contexts in Zhang's formulas: Xuan (Vertigo/Dizziness), Ji (Palpitations), and Ke (Cough). Differentiating similar symptoms reveals truths consistent with vomiting and thirst. Vertigo can result from Lung Wei (Flaccidity) causing upper deficiency, loss of Essence causing lower depletion, or Gu Dan (Grain Jaundice) due to diet; Fuling should not be applied indiscriminately. However, if Zhi Yin is under the heart causing severe Mao Xuan (dizziness with a sensation of being covered/muffled), Fuling is applicable. Note that Zexie Tang (Alisma Decoction) uses Zexie for Mao Xuan even without thirst, as Zexie specializes in this symptom. Adding Fuling might counteract Zexie's upward action, compromising efficacy. Baizhu dispels fluids and stabilizes the Middle, supporting Zexie effectively, so Baizhu is preferred over Fuling. What distinguishes Mao from Fei Mao? "Mao" implies Upper Yang blocked by fluids from entering Lower Yin, causing Yang to float upwards like a cover, representing excess Yang. Zexie drains water and supplements Yin to resolve this. If fluids overwhelm and Upper Yang cannot contend with Yin, Yin and fluids combine to cause vertigo, representing excess Yin. Fuling, possessing harmonious Yang nature and excelling in transforming Qi, causes water to retreat and Yang to expand. Zhang has many such formulas for vertigo.
Water retention under the heart causing vertigo also causes Ji (palpitations). Vertigo is external, Ji is internal; though different manifestations, they share the same source. Stabilizing vertigo stabilizes Ji. Heart Ji is caused by water invading the Heart; Umbilical Ji originates from the Kidneys. Thus, Fuling may not be the sole remedy. However, water from all three Jiao should exit via urination, making Fuling essential. Initially, Umbilical Ji may occur, later leading to Heart Ji ("Water in Kidney causes Heart Ji"). Palpitations not treated by Fuling include those managed by Xiaojianzhong Tang (Minor Construct the Middle Decoction), Guizhi Gancao Tang (Cinnamon Twig and Licorice Decoction), and Zhigancao Tang (Baked Licorice Decoction), which require warming the Middle and tonifying Heart Yang. Fuling's diuretic nature might harm healthy Qi, so it is excluded.
Causes of Ke (cough) are numerous; Fuling manages coughs due to Phlegm-Fluids. However, some Phlegm-Fluid cases are unsuitable for Fuling: Banxia Mahuang Tang (Pinellia and Ephedra Decoction) treats Phlegm-Fluid with palpitations by using Mahuang (Ephedra) to vent Heart Yang via the exterior; Xu Zhongke calls this "Old Phlegm," which cannot be resolved by leaching. Gansui Banxia Tang (Kansui and Pinellia Decoction) treats retained fluid with purging, using Gansui (Kansui), Gancao, and Shaoyao (Peony) to purge downwards; forcing it via urine would be erroneous. Other Phlegm-Fluid cases requiring acrid dispersion or bitter descent are excluded. Cough is a Lung disease; Fuling's downward leaching fails to resolve Lung pathogens, so it is rarely used for cough. It is effective only when Chong Qi (Rebellious Qi) carries Phlegm-Fluids upward causing chest fullness. Then, Fuling's downward drainage works swiftly. Thus, Fuling treats Phlegm-Fluids, not cough per se; it treats Fluids, not Phlegm. Linggui Zhugan Tang (Poria, Cinnamon Twig, Atractylodes, and Licorice Decoction) treats Phlegm-Fluids miraculously, with Fuling as the sovereign herb to guide subtle fluids out via urine, highlighting the necessity of Fuling for Phlegm-Fluids.
Its ability to drain water/fluids from all three Jiao via urination stems from its properties. Fuling is sweet and bland, a correct herb for the Stomach. Its pure white color associates it with the Lung. The Lung governs skin/hair and corresponds to the Taiyang (Greater Yang) channel. Thus, it enters Taiyang. Its bland nature allows entry from skin/hair into Taiyang Fu organs. Lung and Stomach govern descending; Bladder Qi transformation expels urine. This gives its diuretic effect a momentum like water flowing from a high roof. Zhang adds Fuling for difficult urination for this reason.
Promoting urination is Zhang's explicit instruction and a classic tradition. It should not be confused with curing Xiao Ke (Wasting-Thirst). Does promoting urination exhaust its utility? No. Reviewing Zhang's formulas: Shenqi Wan (Kidney Qi Pill) treats difficult urination, Xiao Ke, and frequent urination. Difficult urination indicates Kidney Yin obstruction; Fuling with Guizhi/Fuzi unblocks it. Frequent urination indicates Kidney Yang weakness; Fuling with Guizhi/Fuzi strengthens it. It is also used for exterior dampness (Fangji Fuling Tang), throat obstruction (Banxia Houpo Tang), Chest Bi (Fuling Xingren Gancao Tang), abdominal masses (Guizhi Fuling Wan), tonics (Shuyu Wan), and wind-dispelling formulas (Houji Heisan). Only Fuling, with its sweet-bland taste and mild nature, transforms water within Qi and Qi within Water, adapting to various complex roles while adhering to this principle. Without proper preparation, its true efficacy is lost, and harm may occur.