知母为肺胃肾三经清气热之药，洁古、东垣、丹溪，咸以知母与黄柏为滋阴之品，后人
遂视为补剂。知母之润，虽不似黄柏之燥，然寒滑下行，使热去而阴生则有之，究无补性能
益阴之不足。即以泻邪火，亦当适可而止。否则降令太过，脾胃受伤，真阳暗损，诚有如李
濒湖所言者。
散皆无知母，白虎汤有知母而无渴证，加人参乃始治渴。盖以阳明热盛，清热诚要；然膏知
无益阴生津之能，于清热之中再加以人参，则病去而正即复，其用意之周密，千金外台且逊
之，
桂枝芍药知母汤，仲圣之用知母，即本经所谓除邪气肢体浮肿下水者。邹氏解之，但以
知母为治火阻于下，则未免肤浅。试历引他说以补之∶张隐庵云∶知母皮外有毛，故除皮毛
之邪气；肉浓皮黄，兼得土气，故治肢体浮肿。张石顽云∶除邪气肢体浮肿，是指湿热水气
而言。叶香岩云∶肾恶燥，燥则开阖不利而水反蓄，知母寒滑，滑利关门而水自下。合观三
说，而此方之用知母，可晓然矣。
邹氏云∶脾主升举清阳，胃主通降浊阴，皆属土而畏湿。术开花于初夏，结实于伏时，
偏于湿热弥漫之际，显其有猷有为，确知其入脾胃，能力固中气，外御湿侮矣。刘氏亦脾胃
同论，而以为先胃而后及脾。张隐庵则专主益脾而不及胃。窃思胃为阳明燥金，脾为太阳湿
土，土必名湿者，即隐庵所谓土有湿气，始能灌溉四旁，如地得雨露而后发生万物也。白术
味甘多脂，有似湿土，非脾之正药而何。其肉白，老则微红，味复带辛，故能由脾及胃而达
肌表
白术除脾湿，固中气，为中流之砥柱。其散表邪，非辅以麻黄桂枝附子之属，不能由肌
肉而透皮毛。盖其味浓而甘，擅长于守也。麻黄桂枝附子，为走散风寒之剂，加以白术除湿
，则为治风湿，治寒湿。无湿不加，故麻黄桂枝附子多用于伤寒太阳病，而术惟有水气始用
之。邹氏云∶仲圣治风寒湿痹方，多有不用术者，以术于风胜湿胜者为最宜，寒胜者差减。
盖风胜必烦，湿胜必重。金匮中治痹用术诸方，非兼烦必兼重。或云身烦疼，或云身体疼烦
，或云骨节烦疼掣痛，或云腹重，或云头重，或不烦不重，而云身体疼、手足寒、骨节痛，
是析风与湿与寒而三之矣。不知仲圣方言烦者未尝不兼湿，言重者未尝不兼风，言寒者未尝
不兼风与湿，核诸本经主风寒湿痹，无不吻合。邹氏徒泥于字面而不知细审，遂并白术性用
而胥失之矣。
凡仲圣方用桂至四两，必为利小便与下肾邪，桂枝附子去桂加白术汤，又明云大便硬小
便自利去桂，大便不硬小便不利当加桂，是桂枝之能利小便无疑矣。乃尤氏解此方云∶大便
硬小便自利，知其人在表之阳虽弱，而在里之气自治。则皮中之湿，所当驱之于里，使水从
水道而出，不必更出之表以危久弱之阳，故去桂枝之辛散，加白术之苦燥，合附子之大力健
行者，于以并走皮中逐水气。夫去桂以小便利也。今去桂而犹欲驱湿从水道出，不知其意何
居。况既云当驱之于里，不必更出之表，而又云加白术合附子，以并走皮中逐水气，不仍出
之于表乎。是尤氏于本条语意，全未体会。邹氏之说，差胜于尤，而亦未见其当。其解去桂
加术也。曰∶脾健则能制水，水在内能使下输膀胱而大便实，水在外能使还入胃中而大便濡
。夫谓使在内之水下输膀胱，实非术之能事。仲圣加术，正取其不利小便。谓使在外之水还
入胃中，则殆以大便硬而更崇其土，理不可晓，作此当然之想耳。按仲圣云，三服尽其人如
冒状勿怪，此以术附并走皮中，逐水气未得除，故使之耳。可见术附并用，是使水从表除，
不从里泄，即水不还入胃中之据。或谓如大便硬何。曰∶小便数者，大便必硬，此小便自利
，即小便数也。皮中之水不当留而留，水府之水当留而不留，脾不举其职，而肠胃与膀胱之
传化咸乖矣。去桂加术，则小便节而本有之津液不随之而亡，亦脾职复而后致之津液可由是
而裕；水湿外除，津液内蒸，谁谓白术之加，不足以濡大便哉。
白术大明主反胃、利小便，洁古主生津、止渴，殆不善会仲圣方而致误耳。五苓散药止
五味，而交相为用，中多奥旨。夫所谓脉浮发热者，表证也，烦渴小便不利者，里证也。太
阳表邪化热传本，因而渴饮，因而水蓄不化，因而小便不利。解表止桂枝一味，治里亦第利
水而不涤热，且利水用至四味，不更助燥增热乎。要知表未全解，尚属阳中有阴，不似阳明
病可任寒药。水为阴邪，非辛甘温不化，桂枝虽不以利水，而化气必藉桂枝。猪苓茯苓亦太
阳药，协桂枝则利水而亦解表。五味分两皆甚少，且以散服，多饮暖水，为出汗计者至矣。
而治里之法即具于其中。桂枝最少，欲其达表；泽泻最多，取其咸降；更以白术一味益中气
，收水湿，安靖上下；而后表无不解，水无不行。表解水行，则热自撤，渴自止。若谓术能
止渴、利小便，则实非其所长。茯苓泽泻汤治胃反吐，而渴欲饮水。胃反，是脾伤不磨，并
挟饮邪，故以白术健脾胜水，非以止胃反。生姜半夏为治呕吐之专药，方有生姜无半夏者，
以渴忌半夏也。白术味甘多脂，原能生津，观桂枝附子去桂加白术汤之治大便硬可见。然其
性燥，用于有水湿之证，诚能使脾运而津生。若阴虚津枯，责效于白术，则白术谢不敏矣。
术之或去或加，见于理中丸者为多，欲明用术之道，于此求之，思过半矣。曰脐上筑者
，肾气动也。去术加桂四两。肾气动，是欲作奔豚之征兆，以桂四两降而泄之，原有成法，
见于伤寒金匮两书。加桂可矣，去术何为？夫土能制水，故千金以白术治髓溢，似此证正宜
崇土；然术能御之不能泄之，不去术，则术横亘于中，足以掣桂之肘，此加桂所以必去术也
。曰∶吐多者，去术加生姜二两；下多者还用术。猪苓汤、五苓散、茯苓泽泻汤，皆有吐不
去术。生姜泻心汤、黄芩汤、四逆汤、白通汤，皆有下利不用术。兹何为不然？不知此为寒
霍乱言耳。吐多者吐多于下，下多者下多于吐。吐多于下，则里湿尚轻而胃逆为甚，加生姜
是以辛散之，去术为甘壅也。下多于吐，则脾湿重矣，健脾除湿，非术不可。故吐多去之，
而下多必还用之。曰∶渴欲饮水者，加术足前成四两半。术非治渴之物，此不特不去而更加
于前数，何故？盖理中所以温中，所以治寒多不用水之霍乱。今渴欲饮水，自非燥热之渴，
乃因吐利重丧其津，而脾弱不振也。是虽有参以生津，而参以气胜，术以味胜。味胜者培中
土而滋化源，尤为得力，故不加参而加术也。曰∶腹满者去术加附子一枚。洄溪谓阳虚，尤
氏谓气脾，邹氏谓脾实。按证是脾寒，金匮有腹满为寒之文，又观所加为附子，其为阳虚无
疑。若是脾实，则当与以浓朴七物大柴胡大承气之属，与此悬绝矣。四逆温肾用姜附，此温
脾亦用姜附。盖肾寒阳虚，必侵及脾，故以姜辅附。脾寒阳虚，其源由肾，故以附辅姜。其
必去
别录术除心下急满一语，须连上消痰水看；然术不能独任其责，亦惟中虚者宜之。金匮
云∶病痰饮者，当以温药和之。苓桂术甘汤，四味皆相协以成功，无一味可缺。用于伤寒，
则茯苓增一两以急下其水，白术减一两以微损其壅，为其气冲故也。而要非吐下之后，未必
以术补虚。桂枝人参汤，证兼心下痞硬，而其用术也，以数下之后，利下不止，虚亦甚也。
惟桂枝去桂加茯苓白术汤，表证未罢而去桂，心下满痛而加术，几令人不解。然服桂枝汤或
下之，虽不切中病情，而病气亦已衰矣。头项强痛、翕翕发热，而脉不云浮，亦不恶寒恶风
，翕翕乃微开微阖之象，是未可与头痛发热并论者，独水停心下满而微痛、无汗而小便不利
，邪无从出，为是证之关键。盖太阳为寒水之府，头顶乃太阳经脉之所至，若非水停心下，
前服桂枝汤即强痛可除。其不除者，半由寒水之不下行也。桂枝一味，无汗固忌，不治表亦
无需乎桂，故去之。利小盒饭首推茯苓，故加之。水气因阳气不充而停，不益其气，病机不
转，术益气而除湿，故加之。虽然甘壅之术，非满痛之心下所宜，其所以得收其效者，独赖
有芍药以敛之耳。况术为脾家准对之药，得芍药自疾趋而入脾，得茯苓又相协而利水，水行
则满痛必除，太阳之微邪，何至仍踞于表。甘草乃白术补虚之佐使。姜枣调营卫，使邪无所
容，
别录术主大风在身面，其所谓风，即海藏谓术补肝风虚之风。刘氏云∶阳虚阴蓄，久而
阴不化，则阳从之而化风，是谓风虚。又云∶阳蓄阴中则气虚，气虚则生湿。是术之治风仍
不离乎湿。金匮附近效术附汤一方，即治风虚之证也。别录又主风眩头痛目泪出，下句接以
消痰水，盖以风眩本于痰水，消痰水即所以治风眩。邹氏谓湿与水与饮是一源三歧，历举金
匮治眩与治湿治水各方以证之，并谓本经止汗除热，多系风湿相搏之证，如五苓散、防己黄
汤、甘草附子汤，皆止汗除热之验，而不得用于温热之汗出身热，洵属确论。然其于金匮
有不得其解者，谓小半夏加茯苓汤，治饮眩而不用术，以心下痞故。夫小半夏汤治呕吐之方
也，药止三味，而必以小半夏加茯苓名之，明乎此以止呕吐利水为治也。虽然，呕吐因膈间
有水，因膈间有水而眩悸，皆术所宜从事，即心下痞因饥而得者，亦何尝忌术；乃绝不许术
阑入其间，诚不可解。愚盖细思而得其故焉，仲圣下字皆极有斟酌，呕吐而曰卒，卒字讵容
忽过，呕吐由于卒致，则必膈间本无宿水，或因清阳偶弛，饮停不化，遂胃逆而为呕吐。脾
固无恙，无虑其虚。以姜夏宣阳降逆于上，茯苓利水于下，足以疗之而有余。若再以甘壅之
术，横于膈间，则非徒无益，而又害之矣。枳实薤白桂枝汤之治胸痹也，曰人参汤亦主之，
一证而虚实不同，药即攻补相反，术之宜与不宜，不益可见哉。
知母是清除肺、胃、肾三经气分热邪的药物。洁古（张元素）、东垣（李杲）、丹溪（朱震亨）都认为知母与黄柏是滋阴的药材，后人便将其视为补益剂。知母的滋润特性，虽然不像黄柏那样燥烈，但它性寒滑利而下行，确实能起到去除热邪、滋生阴液的作用，但究其根本，并没有补益性能来增益阴液的不足。即使是用它来泻除邪火，也应当适可而止。否则，降泄之力太过，会损伤脾胃，暗中损耗真阳，这正如李濒湖（李时珍）所说的那样。
《伤寒论》中许多方剂不含知母，白虎汤中含有知母但没有口渴症状，加入人参后才开始治疗口渴。这是因为阳明经热盛，清热固然重要；然而单用知母没有生津增液的功效，在清热的同时加入人参，则病去而正气即复，其用意之周密，连《千金方》和《外台秘要》都逊色一筹。
桂枝芍药知母汤中，张仲景使用知母，正是依据《本经》所说的“除邪气，肢体浮肿，下水”。邹氏对此的解释，仅认为知母是治疗火邪阻滞于下焦，未免过于肤浅。试引用其他医家的说法来补充：张隐庵说：“知母皮外有毛，所以能祛除皮毛的邪气；肉质浓厚、外皮色黄，兼得土气，所以能治疗肢体浮肿。”张石顽说：“‘除邪气，肢体浮肿’，指的是湿热水气而言。”叶香岩说：“肾恶燥，燥则开阖不利而水反蓄积，知母性寒滑，滑利关门而水自然下行。”综合这三种说法，这个方子中使用知母的道理就可以明白了。
邹氏说：“脾主升举清阳，胃主通降浊阴，二者皆属土而畏湿。白术开花于初夏，结实于伏暑时节，偏偏在湿热弥漫之际，显现出它的作为，确知它进入脾胃，能够巩固中气，抵御外湿的侵犯。”刘氏也将脾胃同论，但认为先作用于胃而后波及脾。张隐庵则专门主张益脾而不涉及胃。我私下思考，胃为阳明燥金，脾为太阳湿土，之所以称脾为湿土，就是张隐庵所说的“土有湿气，始能灌溉四旁”，就像大地得到雨露后才能发生万物一样。白术味甘且多脂，类似湿土，如果不是脾的正药又是什么？它的肉色白，老熟后微红，味道又带辛，所以能从脾及胃而达肌表。
白术能祛除脾湿，巩固中气，是中流的砥柱。它发散表邪，如果不辅以麻黄、桂枝、附子这类药物，就不能从肌肉透达皮毛。大概因为它的味道浓厚而甘，擅长守中。麻黄、桂枝、附子是走散风寒的药剂，加上白术除湿，就成为治疗风湿、寒湿的方子。如果没有湿邪就不加白术，所以麻黄、桂枝、附子多用于伤寒太阳病，而白术只有在水气病时才使用。邹氏说：“张仲景治疗风寒湿痹的方剂中，有很多不用白术的，因为白术最适合风胜或湿胜的情况，对于寒胜的情况效果稍减。”大概风胜必然伴有烦扰，湿胜必然伴有沉重感。《金匮要略》中治疗痹症使用白术的各方，不是兼有烦扰就是兼有沉重。有的说身体烦疼，有的说身体疼烦，有的说骨节烦疼掣痛，有的说腹部沉重，有的说头部沉重，或者不烦不重，只说身体疼痛、手足寒冷、骨节痛，这是将风、湿、寒三者分开论述了。不知道张仲景说“烦”的时候未尝不兼有湿，说“重”的时候未尝不兼有风，说“寒”的时候未尝不兼有风与湿，对照《本经》主治风寒湿痹，无不吻合。邹氏只是拘泥于字面意思而不知仔细审察，于是对白术的药性作用全都理解错了。
凡是张仲景的方子中用到桂枝达到四两的，一定是为了利小便和下泄肾邪。《桂枝附子去桂加白术汤》又明确说大便硬、小便自利的要去掉桂枝，大便不硬、小便不利的应当加桂枝，这说明桂枝能利小便是毫无疑问的。然而尤氏解释这个方子说：“大便硬、小便自利，知道此人在表的阳气虽弱，但在里的气机能自治。那么皮中的湿邪，应当驱赶到体内，使水从水道排出，不必再排出体表以危害久弱的阳气，所以去掉桂枝的辛散，加入白术的苦燥，配合附子的强力健行，从而共同走窜皮中驱逐水气。”既然去掉桂枝是因为小便已利，现在去掉桂枝却还想把湿邪从水道排出，不知道他的用意何在。况且既然说应当驱赶到体内，不必再排出体表，却又说加白术合附子，共同走窜皮中驱逐水气，这不还是排出到体表吗？这说明尤氏对本条经文的意思完全没有体会。邹氏的说法比尤氏稍好，但也未见得当。他解释去桂加术时说：“脾健则能制水，水在内能使下输膀胱而大便实，水在外能使还入胃中而大便濡。”如果说使在体内的水下输膀胱，这实在不是白术的功能。张仲景加白术，正是取其不利小便。如果说使在体外的水还入胃中，那大概是认为大便硬所以要更崇补其土，道理不可晓，只是作这种理所当然的设想罢了。按张仲景说：“三服尽，其人如冒状，勿怪，此以术附并走皮中，逐水气未得除，故使之耳。”可见术附并用，是使水从表除去，不从里排泄，这就是水不还入胃中的证据。有人问如果大便硬怎么办？回答说：小便频数的人，大便必硬，这里的小便自利，就是小便频数。皮中的水不当留而留，水府的水当留而不留，脾不执行其职，肠胃与膀胱的传化功能都失常了。去掉桂枝加入白术，则小便节制而本有的津液不随之流失，也是脾职恢复后生成的津液可以由此而充裕；水湿从外除去，津液在内蒸腾，谁说加入白术不足以濡润大便呢？
《大明本草》记载白术主治反胃、利小便，《洁古本草》记载主治生津、止渴，这大概是不善于领会张仲景方义而导致误解。五苓散药物只有五味，而相互为用，其中多有奥妙。所谓脉浮发热，是表证；烦渴、小便不利，是里证。太阳表邪化热传入本经，因而口渴饮水，因而水蓄积不化，因而小便不利。解表只用桂枝一味，治里也只是利水而不涤热，而且利水用了四味药，难道不会更助燥增热吗？要知道表邪未完全解除，尚属阳中有阴，不像阳明病可以任用寒药。水为阴邪，非辛甘温不能化气，桂枝虽然不以利水见长，但化气必须借助桂枝。猪苓、茯苓也是太阳经药，协同桂枝则利水同时也解表。五味药的剂量都很少，且以散剂服用，多饮暖水，作为出汗的措施已经周全了。而治里的方法就包含在其中。桂枝用量最少，想让它达表；泽泻用量最多，取它咸味下降；再用白术一味益中气，收水湿，安靖上下；然后表邪无不解，水湿无不行。表解水行，则热自撤，渴自止。如果说白术能止渴、利小便，那实在不是它的长处。茯苓泽泻汤治疗胃反呕吐，而渴欲饮水。胃反，是脾伤不能磨运，并挟带饮邪，所以用白术健脾胜水，不是为了止胃反。生姜、半夏是治疗呕吐的专药，方中有生姜无半夏的，是因为口渴忌讳半夏。白术味甘多脂，原本能生津，看《桂枝附子去桂加白术汤》治疗大便硬就可以明白。然而它性燥，用于有水湿的病症，确实能使脾运化而津液生。如果是阴虚津枯，指望白术见效，那白术就力所不及了。
白术的去留加减，在理中丸中体现得最多，想要明白使用白术的道理，从这里寻求，思过半矣。原文说：“脐上筑者，肾气动也。去术加桂四两。”肾气动，是欲作奔豚的征兆，用桂枝四两降而泄之，原有成法，见于《伤寒论》和《金匮要略》两书。加桂是可以的，为什么要去术？土能制水，所以《千金方》用白术治髓溢，像这样的证候正宜崇土；然而白术能御制而不能泄降，不去白术，则白术横亘于中，足以牵制桂枝的作用，这就是加桂所以必须去术的原因。原文说：“吐多者，去术加生姜二两；下多者还用术。”猪苓汤、五苓散、茯苓泽泻汤，都有呕吐但不去白术。生姜泻心汤、黄芩汤、四逆汤、白通汤，都有下利而不用白术。为什么这里不同？不知道这是针对寒霍乱说的。吐多者吐多于下，下多者下多于吐。吐多于下，则里湿尚轻而胃气上逆严重，加生姜是以辛散之，去白术是因为它甘壅。下多于吐，则脾湿重了，健脾除湿，非白术不可。所以吐多去之，而下多必还用之。原文说：“渴欲饮水者，加术足前成四两半。”白术不是治渴之物，这里不仅不去反而更加在前面的数量上，为什么呢？大概理中丸是用来温中，治疗因寒多而不用水的霍乱。现在渴欲饮水，自然不是燥热之渴，而是因为吐利重伤津液，而脾弱不振。因此虽然有参以生津，但参以气胜，术以味胜。味胜者培补中土而滋生化之源，尤为得力，所以不加参而加术。原文说：“腹满者去术加附子一枚。”洄溪认为是阳虚，尤氏认为是气滞，邹氏认为是脾实。按证候是脾寒，《金匮要略》有腹满为寒的条文，又看所加的是附子，其为阳虚无疑。如果是脾实，则应当给予厚朴七物汤、大柴胡汤、大承气汤之类的药物，与此截然不同。四逆汤温肾用姜附，此方温脾也用姜附。大概肾寒阳虚，必侵及脾，所以以姜辅佐附子。脾寒阳虚，其源由肾，所以以附子辅佐姜。必须去掉白术。
《别录》记载白术除心下急满一语，须连上文的消痰水来看；然而白术不能独自承担这个责任，也只适合中虚者。《金匮要略》说：“病痰饮者，当以温药和之。”苓桂术甘汤，四味药皆相协以成功，无一味可缺。用于伤寒，则茯苓增一两以急下其水，白术减一两以微损其壅，因为其气冲的缘故。而且并非在吐下之后，未必会用白术补虚。桂枝人参汤，证兼心下痞硬，而其使用白术，是因为经过多次攻下之后，利下不止，虚也很严重。只有桂枝去桂加茯苓白术汤，表证未罢而去掉桂枝，心下满痛而加白术，几乎令人不解。然而服用桂枝汤或攻下之后，虽然未切中病情，但病气也已衰了。头项强痛、翕翕发热，而脉不浮，也不恶寒恶风，翕翕乃微开微阖之象，是不能与头痛发热并论的，唯独水停心下满而微痛、无汗而小便不利，邪无从出，是这个证候的关键。大概太阳为寒水之府，头顶乃太阳经脉之所至，如果不是水停心下，前服桂枝汤即强痛可除。其不除者，一半是由寒水不下行所致。桂枝一味，无汗固忌，不治表亦无需乎桂，所以去掉它。利小便首推茯苓，所以加入它。水气因阳气不充而停，不益其气，病机不转，白术益气而除湿，所以加入它。虽然甘壅的白术，不适合满痛的心下部位，它能收效的原因，全赖有芍药来收敛它。况且白术是脾家的准对之药，得芍药自然疾趋而入脾，得茯苓又相协而利水，水行则满痛必除，太阳的微邪，何至于仍踞于表。甘草是白术补虚的佐使。姜枣调和营卫，使邪无所容。
《别录》记载白术主大风在身面，其所谓风，即海藏所说的白术补肝风虚之风。刘氏说：“阳虚阴蓄，久而阴不化，则阳从之而化风，是谓风虚。”又说：“阳蓄阴中则气虚，气虚则生湿。”所以白术治风仍不离乎湿。《金匮要略》附近效验的术附汤一方，就是治疗风虚的证候。《别录》又主治风眩头痛目泪出，下句接以消痰水，盖以风眩本于痰水，消痰水即所以治风眩。邹氏认为湿与水与饮是一源三歧，历举《金匮》治眩与治湿治水各方以证明，并认为《本经》止汗除热，多系风湿相搏之证，如五苓散、防己黄芪汤、甘草附子汤，都是止汗除热的验案，而不能用于温热之汗出身热，确实是确论。然而他对《金匮》中有一处不得其解，认为小半夏加茯苓汤，治疗饮眩而不用白术，是因为心下痞的缘故。夫小半夏汤是治疗呕吐的方子，药止三味，而必以小半夏加茯苓名之，明乎此是以止呕吐利水为治。虽然，呕吐因膈间有水，因膈间有水而眩悸，都是白术所适宜治疗的，即使心下痞因饥而得的，又何曾忌讳白术；竟然绝对不许白术阑入其间，实在不可解。我细细思考而得其缘故，张仲景下字皆极有斟酌，呕吐而曰“卒”，“卒”字岂容忽过，呕吐由于猝致，则必膈间本无宿水，或因清阳偶弛，饮停不化，遂胃逆而为呕吐。脾固无恙，无虑其虚。以姜夏宣阳降逆于上，茯苓利水于下，足以疗之而有余。若再以甘壅的白术，横于膈间，则非徒无益，而又害之了。枳实薤白桂枝汤治疗胸痹，曰人参汤也主之，一证而虚实不同，药即攻补相反，白术的宜与不宜，不是更可见了吗？
Muzi (Rhizoma Anemarrhenae) is a herb that clears heat from the Qi level of the Lung, Stomach, and Kidney meridians. Jiegu (Zhang Yuansu), Dongyuan (Li Gao), and Danxi (Zhu Zhenheng) all regarded Muzi together with Huangbai (Cortex Phellodendri) as Yin-nourishing agents, and later generations treated them as tonics. Although the moistening property of Muzi is not as drying as Huangbai, its cold and slippery nature directs downward; while it can indeed eliminate heat and generate Yin, fundamentally it lacks the ability to tonify and augment insufficient Yin. Even when used to drain pathogenic fire, one should stop at the appropriate point. Otherwise, excessive descending action will damage the Spleen and Stomach and secretly deplete True Yang, just as Libinhu (Li Shizhen) stated.
Many formulas in *Shanghan Lun* do not contain Muzi. Baihu Tang contains Muzi but does not treat thirst; only after adding Renshen (Radix Ginseng) does it begin to treat thirst. This is because Yangming heat is exuberant, and clearing heat is indeed crucial; however, Muzi alone lacks the ability to generate fluids and nourish Yin. Adding Renshen during the process of clearing heat allows the disease to be eliminated and the healthy Qi to recover immediately. The meticulousness of this intention surpasses even *Qianjin Fang* and *Waitai Miyao*.
In Guizhi Shaoyao Zhimu Tang, Zhang Zhongjing's use of Zhimu aligns with the description in *Ben Jing*: "Eliminate pathogenic factors, limb edema, and promote water discharge." Zou's explanation, which merely considers Zhimu as treating fire obstruction in the lower jiao, is superficial. Let us supplement this by citing other theories: Zhang Yinan said, "The outer skin of Zhimu has hairs, thus it eliminates pathogenic factors from the skin and hair; the flesh is thick and the skin yellow, acquiring the Earth qi, thus it treats limb edema." Zhang Shiwang said, "'Eliminate pathogenic factors, limb edema' refers to damp-heat and water qi." Ye Tianshi said, "The Kidney dislikes dryness; dryness leads to dysfunction of opening and closing, causing water to accumulate. Zhimu is cold and slippery; its slipperiness opens the gateways, allowing water to flow down naturally." Synthesizing these three explanations, the rationale for using Zhimu in this formula becomes clear.
Zou stated, "The Spleen governs the ascending of clear Yang, and the Stomach governs the descending of turbid Yin; both belong to Earth and fear dampness. Baizhu flowers in early summer and fruits during the Dog Days, manifesting its efficacy precisely during the period of rampant damp-heat, confirming its entry into the Spleen and Stomach to consolidate Middle Qi and resist external dampness invasion." Liu also discussed Spleen and Stomach together but believed it acts on the Stomach first and then the Spleen. Zhang Yinan focused solely on benefiting the Spleen without mentioning the Stomach. I ponder that the Stomach is Yangming Dry Metal, while the Spleen is Taiyin Damp Earth. The reason it is called Damp Earth is what Zhang Yinan meant by "Earth with dampness can irrigate the four directions," just as the earth generates all things only after receiving rain and dew. Baizhu is sweet in taste and rich in mucilage, resembling damp Earth; how could it not be the principal herb for the Spleen? Its flesh is white, turning slightly red when old, and its taste carries acridity, enabling it to travel from the Spleen to the Stomach and reach the muscle surface.
Baizhu eliminates Spleen dampness and consolidates Middle Qi, serving as a pillar in midstream. To disperse exterior pathogens, it cannot penetrate from muscles to skin/hair unless assisted by herbs like Mahuang (Herba Ephedrae), Guizhi (Ramulus Cinnamomi), or Fuzi (Radix Aconiti Lateralis Preparata). This is likely because its strong and sweet flavor excels in maintaining stability. Mahuang, Guizhi, and Fuzi are agents that scatter wind-cold; adding Baizhu to remove dampness creates formulas for treating Wind-Damp and Cold-Damp. Without dampness, Baizhu is not added; thus, Mahuang, Guizhi, and Fuzi are mostly used for Taiyang disease in *Shanghan*, whereas Baizhu is used only when there is water qi. Zou stated, "In Zhang Zhongjing's formulas for treating Bi syndrome caused by wind-cold-damp, many do not use Baizhu, as Baizhu is most suitable for cases dominated by wind or damp, but less effective for those dominated by cold." Generally, wind dominance causes vexation, and damp dominance causes heaviness. In the formulas in *Jinkui Yaolue* treating Bi with Baizhu, there is either vexation or heaviness. Some mention body vexation and pain, some body pain and vexation, some joint vexation and pulling pain, some abdominal heaviness, some head heaviness, or neither vexation nor heaviness but only body pain, cold hands and feet, and joint pain. This separates wind, damp, and cold into three categories. However, one must not overlook that when Zhongjing mentions "vexation," damp may be present; when he mentions "heaviness," wind may be present; when he mentions "cold," both wind and damp may be present. Comparing this with *Ben Jing*'s indication for wind-cold-damp Bi, everything matches perfectly. Zou merely stuck to literal meanings without careful examination, thereby misunderstanding the properties and uses of Baizhu entirely.
Whenever Zhang Zhongjing uses Guizhi up to four liang, it is invariably to promote urination and drain kidney pathogens. *Guizhi Fuzi Qugui Ji Baizhu Tang* explicitly states: if stool is hard and urination is normal, remove Guizhi; if stool is not hard and urination is difficult, add Guizhi. This undoubtedly proves Guizhi's ability to promote urination. However, You Shi interpreted this formula saying: "Hard stool and normal urination indicate that although exterior Yang is weak, interior Qi functions autonomously. Therefore, dampness in the skin should be driven inward so water exits via the urinary tract, rather than being expelled outward to endanger the weakened Yang. Thus, Guizhi's pungent dispersal is removed, and Baizhu's bitter dryness is added, combined with the powerful movement of Fuzi, to jointly attack the skin and drive out water qi." If Guizhi is removed because urination is already free, why still aim to drive dampness out through the urinary tract? Furthermore, if one says it should be driven inward and not outward, yet claims adding Baizhu and Fuzi attacks the skin to drive out water, isn't that still expelling it outward? This shows You Shi completely failed to grasp the meaning of the text. Zou's interpretation is slightly better but still flawed. He explained removing Guizhi and adding Baizhu as: "When the Spleen is healthy, it controls water; water inside flows to the Bladder making stool solid, water outside returns to the Stomach making stool moist." Claiming Baizhu makes internal water flow to the Bladder is incorrect; Zhongjing adds Baizhu precisely because it does not promote urination. Claiming external water returns to the Stomach implies reinforcing Earth due to hard stool, a logic that is obscure and merely speculative. According to Zhongjing: "After taking three doses, the patient feels dizzy; do not be alarmed. This is because Baizhu and Fuzi move together in the skin, driving out water qi which has not yet been fully eliminated." This confirms that Baizhu and Fuzi work together to expel water via the exterior, not the interior, proving water does not return to the Stomach. Someone might ask, what about hard stool? The answer is: frequent urination leads to hard stool. Here, "normal urination" means frequent urination. Water滞留 in the skin should not stay, and water in the reservoir should stay but doesn't; the Spleen fails in its duty, and the transmission of the intestines and Bladder is disrupted. Removing Guizhi and adding Baizhu regulates urination so existing fluids are not lost, and as Spleen function recovers, new fluids are generated; with external dampness removed and internal fluids steaming, who says adding Baizhu is insufficient to moisten the stool?
*Daming Bencao* records Baizhu treating regurgitation and promoting urination; *Jiegu Bencao* records it generating fluids and stopping thirst. These are likely errors resulting from failing to understand Zhongjing's formulas properly. *Wuling San* consists of only five ingredients interacting with profound principles. Pulse floating and fever are exterior signs; vexation, thirst, and dysuria are interior signs. Taiyang exterior pathogen transforming into heat transmits to the interior, causing thirst and drinking, leading to water accumulation and failure to transform, hence dysuria. For releasing the exterior, only Guizhi is used; for treating the interior, only diuresis is employed without clearing heat. Using four ingredients for diuresis might increase dryness and heat. One must know that since the exterior is not fully resolved, it belongs to Yang containing Yin, unlike Yangming disease where cold herbs can be freely used. Water is a Yin pathogen, requiring Pungent, Sweet, and Warm herbs to transform. Although Guizhi is not primarily for diuresis, Qi transformation relies on it. Zhu Ling and Fu Ling are also Taiyang herbs; cooperating with Guizhi, they promote diuresis and release the exterior. The dosages of all five ingredients are small, taken as powder, with instructions to drink warm water to induce sweating—a comprehensive approach. Yet, the method for treating the interior is embedded within. Guizhi is used minimally to reach the exterior; Ze Xie is used maximally for its salty descent; Baizhu is used to benefit Middle Qi, collect water dampness, and stabilize upper and lower. Then the exterior is resolved, and water moves. Once the exterior is resolved and water moves, heat withdraws, and thirst stops. To claim Baizhu stops thirst and promotes urition is to misunderstand its strengths. *Fuling Zexie Tang* treats gastric regurgitation with thirst for water. Gastric regurgitation indicates Spleen injury failing to grind, accompanied by fluid retention; thus Baizhu is used to strengthen the Spleen and overcome water, not to stop regurgitation. Shengjiang and Banxia are specific for vomiting; the formula has Shengjiang but no Banxia because Banxia is contraindicated in thirst. Baizhu is sweet and mucilaginous, originally capable of generating fluids, as seen in *Guizhi Fuzi Qugui Ji Baizhu Tang* treating hard stool. However, its nature is drying; in cases with dampness, it indeed enables Spleen transport and fluid generation. But in Yin deficiency with fluid exhaustion, relying on Baizhu would be ineffective.
The addition or removal of Baizhu appears frequently in Lizhong Wan. To understand its usage, look here, and you will have grasped more than half. The text states: "Sensation of pounding above the navel indicates Kidney Qi moving. Remove Baizhu, add four liang of Guizhi." Kidney Qi moving is a precursor to Ben Tun (running piglet). Using Guizhi to descend and drain is an established method found in both *Shanghan Lun* and *Jinkui Yaolue*. Adding Guizhi is fine, but why remove Baizhu? Earth controls Water, so *Qianjin Fang* uses Baizhu to treat marrow overflow; such a case seems to suit reinforcing Earth. However, Baizhu can restrain but not drain. If Baizhu is not removed, it obstructs the middle, hindering Guizhi's action; hence, Guizhi requires removing Baizhu. The text states: "For excessive vomiting, remove Baizhu and add two liang of Shengjiang; for excessive diarrhea, use Baizhu again." *Zhuling Tang*, *Wuling San*, and *Fuling Zexie Tang* all treat vomiting without removing Baizhu. *Shengjiang Xiexin Tang*, *Huangqin Tang*, *Sini Tang*, and *Baitong Tang* all treat diarrhea without using Baizhu. Why is this different? This refers to Cold Huoluan. In excessive vomiting, vomiting exceeds diarrhea; in excessive diarrhea, diarrhea exceeds vomiting. When vomiting exceeds diarrhea, interior dampness is light but Stomach rebellion is severe; adding Shengjiang disperses with pungency, and removing Baizhu avoids its cloying sweetness. When diarrhea exceeds vomiting, Spleen dampness is heavy; strengthening the Spleen and removing dampness requires Baizhu. Hence, remove for vomiting, use for diarrhea. The text states: "For thirst desiring water, add Baizhu to make four liang and half." Baizhu is not for treating thirst. Why add it instead of removing it? *Lizhong Tang* warms the Middle to treat Huoluan with cold and aversion to water. Thirst desiring water here is not due to dry-heat, but due to loss of fluids from severe vomiting/diarrhea and weak Spleen. Although Renshen generates fluids via Qi, Baizhu generates fluids via Taste. Reinforcing Middle Earth and nourishing the source of transformation is particularly effective, hence Baizhu is added instead of Renshen. The text states: "For abdominal fullness, remove Baizhu and add one piece of Fuzi." Huixi attributes this to Yang deficiency; You Shi to Qi stagnation; Zou to Spleen excess. The syndrome is Spleen Cold; *Jinkui* has texts stating abdominal fullness is Cold. Adding Fuzi confirms Yang deficiency. If it were Spleen Excess, one would use Houpo Qi Wu Tang, Da Chaihu Tang, or Da Chengqi Tang, which are vastly different. *Sini Tang* warms the Kidney with Jiang and Fu; this warms the Spleen with Jiang and Fu. Kidney Cold/Yang deficiency invades the Spleen, so Jiang assists Fu. Spleen Cold/Yang deficiency originates from the Kidney, so Fu assists Jiang. Baizhu must be removed.
*Bielu* states Baizhu removes urgency and fullness below the heart; this must be read together with eliminating phlegm-fluids. However, Baizhu cannot act alone and is suitable only for Middle Deficiency. *Jinkui* states: "For phlegm-fluid diseases, harmonize with warm herbs." *Ling Gui Zhu Gan Tang* succeeds through the cooperation of all four ingredients; none can be omitted. In *Shanghan*, Fu Ling is increased by one liang to urgently drain water, and Baizhu is decreased by one liang to slightly reduce congestion, due to Qi rushing. Moreover, Baizhu is not necessarily used for tonifying deficiency after purging/vomiting. *Guizhi Renshen Tang* treats epigastric hardness/fullness; Baizhu is used because after multiple purgations, diarrhea persists and deficiency is severe. Only in *Guizhi Qugui Ji Fuling Baizhu Tang*, where exterior signs remain but Guizhi is removed, and epigastric fullness/pain leads to adding Baizhu, is it puzzling. However, after taking Guizhi Tang or purging, even if not precise, pathogenic Qi has weakened. Head/neck stiffness, slight fever, but pulse not floating, no aversion to cold/wind—this slight fever indicates slight opening/closing, distinct from typical headache/fever. The key is water stopping in the heart region causing fullness/mild pain, no sweat, and dysuria, leaving no exit for pathogens. Taiyang is the mansion of Cold Water; the vertex is where Taiyang meridians arrive. If not for water stopping in the heart, previous Guizhi Tang would have relieved stiffness. The persistence is partly due to Cold Water not descending. Guizhi is contraindicated without sweat and unnecessary for exterior treatment here, so it is removed. Fu Ling is首选 for promoting urination, so it is added. Water stops due to insufficient Yang Qi; without boosting Qi, the pathology won't turn. Baizhu boosts Qi and removes dampness, so it is added. Although cloying Baizhu is unsuitable for fullness/pain, its efficacy relies on Shaoyao to astringe it. Baizhu is the specific herb for the Spleen; with Shaoyao it enters the Spleen quickly; with Fu Ling it cooperates to drain water. As water moves, fullness/pain resolves, and Taiyang's mild pathogen won't remain on the exterior. Gan Cao is the assistant for Baizhu's tonification. Jiang and Zao harmonize Ying and Wei, leaving no room for pathogens.
*Bielu* states Baizhu treats severe wind on the body and face; this "wind" refers to Haizang's concept of Baizhu tonifying Liver Wind Deficiency. Liu stated: "Yang deficiency with Yin accumulation, prolonged Yin fails to transform, causing Yang to transform into Wind, called Wind Deficiency." Also: "Yang accumulating in Yin causes Qi deficiency; Qi deficiency generates dampness." Thus, Baizhu's treatment of wind still revolves around dampness. The efficacious *Zhufu Tang* nearby in *Jinkui* treats Wind Deficiency syndromes. *Bielu* also treats wind vertigo, headache, and tearing, followed by eliminating phlegm-fluids, implying wind vertigo stems from phlegm-fluids; eliminating phlegm-fluids treats wind vertigo. Zou argued that damp, water, and fluid share one source but three branches, citing *Jinkui* formulas for vertigo, damp, and water to prove this, and stating *Ben Jing*'s "stop sweating and relieve heat" applies mostly to Wind-Damp combusting, such as *Wuling San*, *Fangji Huangqi Tang*, and *Gancao Fuzi Tang*, which are verified treatments, but cannot be used for heat-induced sweating and fever. This is indeed accurate. However, he was puzzled by a case in *Jinkui*: *Xiao Banxia Ji Fuling Tang* treats fluid vertigo without Baizhu due to epigastric stuffiness. *Xiao Banxia Tang* treats vomiting; with only three ingredients, naming it *Xiao Banxia Ji Fuling Tang* clarifies the treatment aims to stop vomiting and promote urination. Although vomiting due to fluid between the diaphragm, and vertigo/palpitations from such fluid, are indications for Baizhu, even epigastric stuffiness caused by hunger does not strictly contraindicate Baizhu. Yet, absolutely excluding Baizhu is inexplicable. After careful thought, I found the reason: Zhongjing's word choice is precise. Vomiting described as "acute/sudden" (*cu*) cannot be ignored. Acute vomiting implies no pre-existing fluid in the diaphragm, possibly due to temporary relaxation of Clear Yang, causing fluid retention and failure to transform, leading to Stomach rebellion and vomiting. The Spleen is intact, not deficient. Ginger and Banxia ascend Yang and descend rebellion above; Fu Ling drains water below; this is sufficient. Adding cloying Baizhu across the diaphragm would be harmful, not helpful. *Zhishi Xiebai Guizhi Tang* treats Chest Bi, stating *Renshen Tang* also treats it. One syndrome, differing in deficiency/excess, with opposing attacking/tonifying drugs; the appropriateness of Baizhu is clearly visible.