知母，味苦、辛，气大寒，沉而降，阴也，无毒。入足少阴、阳明，又入手太阴。最善
泻胃
、肾二经之火，解渴止热，亦治久疟。此物只可暂用，而不可久服。丹溪加入六味丸中，亦
教人暂服，以泻肾中浮游之火，非教人长服也。近世竟加知母、黄柏，谓是退阴虚火热之圣
方，令人经年长用，以致脾胃虚寒，不能饮食，成痨成瘵者，不知几千万人矣。幸薛立斋、
赵养葵论知母过寒，切戒久食，实见到之语，有功于世。总之，此物暂用，以泻胃中之火，
实可夺命；久用，以补肾中之水，亦能促命。谓知母竟可杀人，固非立论之纯，谓知母全可
活人，亦非持说之正也。
或问知母泻肾，肾有补而无泻，不可用知母，宜也。若用之以泻胃，似可常用，何吾子
亦谓
只可暂用乎？曰∶胃火又何可常泻也，五脏六腑皆仰藉于胃，胃气存则生，胃气亡则死。胃
中火盛，恐其消烁津液，用石膏、知母以救胃，非泻胃也。然而石膏过于峻削，知母过于寒
凉，胃火虽救，而胃土必伤，故亦宜暂用以解氛，断不宜常用以损气也。（〔批〕胃为肾之
关门，胃与肾，俱不可用石膏久泻其火，胃寒则肾亦寒也。）
或问知母古人皆言是补肾滋阴妙药，吾子乃言是泻火之味，此余所以疑也。不知母疑也。
天
下味温者能益人，未闻苦寒者而亦益也。知母苦而大寒，其无益于脾胃，又
何必辨。惟是既无益于脾胃，何以泻胃中之火，能夺命于须臾乎。似乎泻即补之之义也。然
而暂用何以相宜，久用何以甚恶？是泻火只可言救肾。而终不可言补肾也。（〔批〕用知母以
救肾，非用知母以补肾，分别独妙。）
或问知母性过寒凉，久服损胃，何不改用他药以救胃，而白虎汤中必用知母，以佐石膏
之横
，不以寒济寒乎？嗟乎。何问之善也。夫白虎汤，乃治胃火之初起，单用石膏以救胃，犹恐
不胜，故又加知母，以止其肾中之火，使胃火之不增焰也。若胃火已炽之后与将衰之时，知
母原不必加入之也。或去知母，而易之天冬、元参之味，亦未为不可也。
或问知母、黄柏用之于六味丸中，朱丹溪之意以治阴虚火动也，是岂无见者乎？嗟乎。
阴虚
火动，六味汤治之足矣，何必又用知母、黄柏以泻火乎。夫火之有余，因水之不足也，补其
水，则火自息矣。丹溪徒知阴虚火动之义，而加入二味，使后人胶执而专用之，或致丧亡，
非所以救天下也。
或问知母既不宜轻用，何不竟删去之，乃既称其功，又辟其过耶？嗟乎。吾言因丹溪而
发，
岂谓知母之等于鸠毒哉。盖知母止可用之以泻胃火之有余，而不可用之以泻肾火之不足，故
泻胃火则救人，而泻肾火则杀人也。丹溪止主泻肾，而不主泻胃，此生死之大关，不可不辨
也。
或问李时珍发明知母是气分之药，黄柏是血分之药。黄柏入肾，而不入肺；知母下润肾，
而
上
清肺金，二药必相须而行，譬之虾之不能离水母也。是黄柏、知母，必须同用为佳，而吾子
谓二药不可共用，得毋时珍非欤？曰∶时珍殆读书而执者也。不知黄柏未尝不入气分，而知
母未尝不入血分也。黄柏清肾中之火，亦能清肺中之火；知母泻肾中之热，而亦泻胃中之热
。胃为多气多血之腑，岂止入于气分，而不入于血分耶？是二药不必兼用，不可即此而悟哉
知母，味苦、辛，气大寒，性沉而降，属阴，无毒。入足少阴肾经、阳明胃经，又入手太阴肺经。最善于清泻胃、肾二经之火，解渴止热，也能治疗久疟。此药只可暂时使用，不可长期服用。朱丹溪将其加入六味丸中，也是教导人们暂时服用，以清泻肾中浮游之火，并非教导人们长期服用。近代人竟然将知母、黄柏加入其中，说是退阴虚火热的神圣方剂，让人常年长期使用，导致脾胃虚寒，不能饮食，形成痨病、瘵病的人，不知有几千万了。幸好薛立斋、赵养葵论述知母过于寒凉，切戒长期食用，确实是见到实情的话，对世人有功。总之，此药暂时使用，以清泻胃中之火，确实可以救命；长期服用，以补肾中之水，也能催命。说知母竟能杀人，固然不是立论纯粹，说知母全能活人，也不是持说正确。
有人问：知母泻肾，肾有补而无泻，不可用知母，这是合理的。如果用知母来清泻胃火，似乎可以常用，为什么您也说只可暂时使用呢？回答说：胃火又怎么可以常泻呢？五脏六腑都仰赖于胃，胃气存则生，胃气亡则死。胃中火盛，恐怕其消烁津液，用石膏、知母来救胃，并不是泻胃。然而石膏过于峻猛削伐，知母过于寒凉，胃火虽被救，而胃土必然受伤，所以也宜暂时使用以解除病势，断不宜常用以损伤正气。（批注：胃为肾之关门，胃与肾，都不可用石膏长期清泻其火，胃寒则肾亦寒。）
有人问：古人皆说知母是补肾滋阴妙药，您却说它是泻火之味，这是我所以疑惑的原因。不知道知母的疑惑所在。天下味温者能益人，未听说苦寒者也能益人。知母苦而大寒，它对脾胃无益，又何必辩驳。只是既然对脾胃无益，为何清泻胃中之火，能在顷刻间夺命呢？似乎是“泻即补”的意思。然而暂时使用为何适宜，长期服用为何有害？这泻火只能说是救肾，而不能说是补肾。（批注：用知母来救肾，不是用知母来补肾，分别得非常精妙。）
有人问：知母性过寒凉，长期服用损胃，为何不改用其他药物来救胃，而在白虎汤中必用知母，以佐助石膏的横行霸道，不以寒济寒吗？唉！这个问题问得好。夫白虎汤，是治疗胃火初起，单用石膏来救胃，还担心不胜任，所以又加知母，以制止肾中之火，使胃火不增焰。若胃火已炽盛之后与将衰之时，知母原不必加入。或者去掉知母，而换成天冬、玄参的味道，也未尝不可以。
有人问：知母、黄柏用在六味丸中，朱丹溪的本意是治疗阴虚火动，这难道没有见识吗？唉！阴虚火动，六味汤治疗它足够了，何必又用知母、黄柏来泻火呢？火之有余，是因为水之不足。补水，则火自息矣。丹溪只知道阴虚火动的道理，而加入这两味药，使后人固执地专用它们，或许会导致丧亡，这不是用来拯救天下的方法。
有人问：知母既然不宜轻用，为何不干脆删去它，却既称赞它的功效，又批判它的过失呢？唉！我的话是因丹溪而发，难道是说知母等于鸠毒吗？大概知母只可用以清泻胃火之有余，而不可用以清泻肾火之不足，所以清泻胃火则救人，而清泻肾火则杀人。丹溪只主泻肾，而不主泻胃，这是生死的大关键，不可不辨明。
有人问：李时珍发明知母是气分之药，黄柏是血分之药。黄柏入肾，而不入肺；知母下润肾，而上清肺金，二药必须相须而行，譬如虾之不能离水母也。是黄柏、知母，必须同用为佳，而您却说二药不可共用，莫非时珍错了吗？回答说：时珍大概是读书而拘执的人。不知道黄柏未尝不入气分，而知母未尝不入血分也。黄柏清肾中之火，也能清肺中之火；知母泻肾中之热，也泻胃中之热。胃是多气多血之腑，岂止入于气分，而不入于血分耶？是二药不必兼用，不可就此而领悟吗？
Mu Mu (Rhizoma Anemarrhenae), with a bitter and acrid taste, is extremely cold in nature, heavy and descending, belonging to Yin, and non-toxic. It enters the Foot Shaoyin (Kidney) Meridian, Yangming (Stomach) Meridian, and also the Hand Taiyin (Lung) Meridian. It is particularly effective in clearing heat fire from the Stomach and Kidney meridians, relieving thirst and stopping heat, and can also treat chronic malaria. This herb should only be used temporarily and not for long-term consumption. Zhu Danxi added it to Liuwei Wan (Six-Ingredient Pill with Rehmannia) to instruct people to take it temporarily, to clear floating fire in the Kidney, not to instruct long-term use. In recent times, people have actually added Mu Mu (Rhizoma Anemarrhenae) and Huang Bai (Cortex Phellodendri), claiming it as a sacred prescription for retreating deficiency heat fire, causing people to use it for years, leading to deficiency-cold of the Spleen and Stomach, inability to eat, and developing consumptive diseases (Lao disease/Zhai disease), numbering tens of millions. Fortunately, Xue Lizhai and Zhao Yangkui discussed that Mu Mu (Rhizoma Anemarrhenae) is too cold and strictly warned against long-term consumption, which are words based on practical observation and beneficial to the world. In short, this herb used temporarily to clear Stomach fire can indeed save lives; used long-term to nourish Kidney water, it can hasten death. To say Mu Mu (Rhizoma Anemarrhenae) can kill is not purely argued; to say it can fully save lives is not correctly held.
Someone asked: Mu Mu (Rhizoma Anemarrhenae) purges the Kidney, and the Kidney has tonification but no purgation, so it should not be used with Mu Mu (Rhizoma Anemarrhenae), which is reasonable. If used to purge Stomach fire, it seems it could be used commonly, why do you also say it can only be used temporarily? I reply: How can Stomach fire be purged constantly? The five Zang organs and six Fu organs all rely on the Stomach. When Stomach Qi exists, there is life; when Stomach Qi perishes, there is death. If Stomach fire is excessive, fearing it will consume body fluids, using Shi Gao (Gypsum Fibrosum) and Mu Mu (Rhizoma Anemarrhenae) to rescue the Stomach is not purging the Stomach. However, Shi Gao (Gypsum Fibrosum) is too harsh and cutting, and Mu Mu (Rhizoma Anemarrhenae) is too cold and cooling. Although Stomach fire is rescued, Stomach Earth will inevitably be injured. Therefore, it is suitable to use temporarily to resolve the pathogenic factor, and absolutely unsuitable to use commonly to damage Qi. (Commentary: The Stomach is the gatekeeper of the Kidney. Neither the Stomach nor the Kidney should have their fire purged long-term with Shi Gao (Gypsum Fibrosum); if the Stomach becomes cold, the Kidney also becomes cold.)
Someone asked: Ancients all said Mu Mu (Rhizoma Anemarrhenae) is a wonderful medicine for tonifying the Kidney and nourishing Yin, but you say it is a substance that purges fire. This is my doubt. One does not know the doubt regarding Mu Mu (Rhizoma Anemarrhenae). Substances with warm flavors benefit people; it has never been heard that bitter and cold substances also benefit. Mu Mu (Rhizoma Anemarrhenae) is bitter and extremely cold; its lack of benefit to the Spleen and Stomach needs no further debate. Since it benefits neither the Spleen nor the Stomach, how can purging Stomach fire save lives in an instant? It seems like "purging is tonifying." But why is temporary use appropriate and long-term use harmful? Purging fire can only be described as rescuing the Kidney, not tonifying the Kidney. (Commentary: Using Mu Mu (Rhizoma Anemarrhenae) to rescue the Kidney is not using it to tonify the Kidney; the distinction is exquisite.)
Someone asked: Mu Mu (Rhizoma Anemarrhenae) is excessively cold and cooling, damaging the Stomach with long-term use. Why not change to other herbs to rescue the Stomach, yet Baihu Tang (White Tiger Decoction) must use Mu Mu (Rhizoma Anemarrhenae) to assist Shi Gao (Gypsum Fibrosum) in its dominance, not using cold to aid cold? Alas, what a good question! Baihu Tang (White Tiger Decoction) treats the initial onset of Stomach fire. Using only Shi Gao (Gypsum Fibrosum) to rescue the Stomach might still be insufficient, so Mu Mu (Rhizoma Anemarrhenae) is added to stop Kidney fire, preventing Stomach fire from increasing its flame. After Stomach fire has become blazing or when it is declining, Mu Mu (Rhizoma Anemarrhenae) need not be added. Or, removing Mu Mu (Rhizoma Anemarrhenae) and substituting with Tian Dong (Radix Asparagi) and Yuan Shen (Radix Scrophulariae) would also be acceptable.
Someone asked: Mu Mu (Rhizoma Anemarrhenae) and Huang Bai (Cortex Phellodendri) are used in Liuwei Wan (Six-Ingredient Pill with Rehmannia). Zhu Danxi's intention was to treat deficiency fire moving due to Yin deficiency. Is this not insightful? Alas, deficiency fire moving due to Yin deficiency can be treated sufficiently by Liuyi Tang (Six-Ingredient Decoction), why add Mu Mu (Rhizoma Anemarrhenae) and Huang Bai (Cortex Phellodendri) to purge fire? Excess fire is due to insufficiency of water. Tonifying water causes fire to subside naturally. Danxi only understood the meaning of deficiency fire moving due to Yin deficiency and added these two herbs, causing later generations to stubbornly use them exclusively, potentially leading to death. This is not a method to save the world.
Someone asked: Since Mu Mu (Rhizoma Anemarrhenae) is not suitable for light use, why not delete it entirely, yet you praise its merits and criticize its faults? Alas, my remarks were triggered by Danxi. Do I mean Mu Mu (Rhizoma Anemarrhenae) is equal to poison? Generally, Mu Mu (Rhizoma Anemarrhenae) can only be used to purge excess Stomach fire, not to purge deficient Kidney fire. Thus, purging Stomach fire saves people, while purging Kidney fire kills people. Danxi focused only on purging the Kidney, not the Stomach. This is a major juncture of life and death, which must be distinguished.
Someone asked: Li Shizhen clarified that Mu Mu (Rhizoma Anemarrhenae) is a herb of the Qi level, and Huang Bai (Cortex Phellodendri) is a herb of the Blood level. Huang Bai (Cortex Phellodendri) enters the Kidney but not the Lung; Mu Mu (Rhizoma Anemarrhenae) moistens the Kidney downward and clears Lung Metal upward. The two herbs must act together, like shrimp cannot live without jellyfish. Thus, Huang Bai (Cortex Phellodendri) and Mu Mu (Rhizoma Anemarrhenae) are best used together. You say they should not be used together. Is Shizhen wrong? I reply: Shizhen probably read books but was rigid. One does not know that Huang Bai (Cortex Phellodendri) does not fail to enter the Qi level, nor that Mu Mu (Rhizoma Anemarrhenae) fails to enter the Blood level. Huang Bai (Cortex Phellodendri) clears Kidney fire and can also clear Lung fire; Mu Mu (Rhizoma Anemarrhenae) purges Kidney heat and also purges Stomach heat. The Stomach is a Fu organ abundant in Qi and Blood; how can it only enter the Qi level and not the Blood level? These two herbs need not be used jointly; one should realize this.