山药，味甘，气温平，无毒。入手足太阴二脏，亦能入脾、胃。治诸虚百损，益气力，
开心
窍，益知慧，尤善止梦遗，健脾开胃，止泻生精。山药可君可臣，用之无不宜者也，多用受
益，少用亦受益，古今颇无异议，而余独有微辞者，以其过于健脾也。夫人苦脾之不健，健
脾，则大肠必坚牢，胃气必强旺而善饭，何故独取而贬之？不知脾胃之气太弱，必须用山药
以健之，脾胃之气太旺，而亦用山药，则过于强旺，反能动火。世人往往有胸腹饱闷，服山
药而更甚者，正助脾胃之旺也。人不知是山药之过，而归咎于他药，此皆不明药性之理也。
盖山药入心，引脾胃之邪，亦易入心。山药补虚，而亦能补实，所以能添饱闷也。因世人皆
信山药有功而无过，特为指出，非贬山药也。山药舍此之外，别无可议矣。
或问山药乃补阴精之物，而吾子谓是健脾胃之品，何子之好异也？曰∶山药益人无穷，
损人
绝少。余谈《本草》，欲使其功过各不掩也。山药有功而无过。言其能助脾胃之火者，是求
过于功之中也。然而天下之人脾胃太旺者，千人中一、二，不可执动火之说，概疑于脾胃之
未旺者，而亦慎用之也，脾胃未旺，则肾气必衰，健脾胃正所以补阴精也。予道其常，何好
异之有。
或问山药补肾，仲景张公所以用之于六味地黄丸中也，然而山药实能健脾开胃，意者六
味丸
非独补肾之药乎？曰∶六味丸实直补肾水之药也，山药亦补肾水之药，同群共济何疑。然而
，六味丸中之用山药，意义全不在此。山药，乃心、肝、脾、肺、肾无经不入之药也。六味
丸虽直补肾中之水，而肾水必分资于五脏，而五脏无相引之使，又何由分布其水，而使之无
不润乎。倘别用五脏佐使之品，方必杂而不纯，故不若用山药以补肾中之水，而又可遍通于
五脏。此仲景张夫子补一顾五，实有鬼神难测之机也。（〔批〕山药补水，而又通五脏，仲
景公所以用之于六味丸中，自有此方，无此妙论。）
或问山药入于六味丸中之义，予既已闻之，不识入于八味丸中，亦有说乎？曰∶八味丸，
由
六味而加增者也，似乎知六味，即可知八味之义矣。谁知八味丸中之用山药，又别有妙义乎
。六味，补肾中之水。而八味，则补肾中之火也。补肾中之火者，补命门之相火也。夫身
之相火有二∶一在肾之中，一在心之外。补肾中之相火，则心外之相火，必来相争，相争
则必相乱，宜豫有以安之，势必下补肾中之火，即当上补心下之火矣。然而既因肾寒而补其
下
，又顾心热以补其上，毋论下不能温其寒，而上且变为热矣。用药之杂，可胜叹哉。妙在用
山药于八味丸中，山药入肾者十之七，入心者十之三，引桂、附之热，多温于肾中，少温于
心外，使心肾二火各有相得，而不致相争，使肾之气通于心，而心之气通于肾，使脾胃之气
安然健运于不息，皆山药接引之功也。仲景公岂漫然用之哉。（〔批〕八味丸，补命门之火
也，补命门之火，虑及心包之火必来相争，用山药解纷，使心肾相通、胃脾两健，何论奇而
理确如此，真仲景公入室之药也。）
或疑山药不宜多用。何以六味地黄丸终年久服而无害也，得毋入于地黄丸可以多用，而
入于
他药之中即宜少用耶？不知山药可以多用而无忌。吾前言脾健之人宜忌者，虑助火以动燥，
而非言其不可以多用也。
或疑山药津滑，何能动燥？曰∶山药生精，自然非助燥之物。吾言其助燥者，助有火之
人，
非助无火之人也。
或问山药色白，何能乌须，何吾子用之为乌须圣药？曰∶山药何能乌须哉。山药入肾，
而尤
通任督。任督之脉，上行于唇颊，故借山药用之于乌芝麻、黑豆、地黄、南烛、何首乌之内
，导引以黑须鬓，非山药之能自乌也。或又问山药既为引导之药，则不宜重用之为君矣。不
知山药虽不变白，而性功实大补肾水者也。肾水不足者，须鬓断不能黑，我所以重用山药而
奏功也。
山药，味道甘甜，药性平和，无毒。它主要归入手经和足经的太阴脏（肺、脾），也能进入脾和胃。治疗各种虚损，益气力，开通心窍，增加智慧，尤其善于止住梦遗，健脾开胃，止泻并生精。山药既可以作为君药也可以作为臣药，使用它没有不适宜的，多用能受益，少用也能受益，古今对此几乎没有异议。但我独自略有微词的原因，是因为它过于健脾了。人们苦于脾不健运，如果健脾，那么大肠必然坚实牢固，胃气必然强旺而食欲好，为什么唯独要选取它并贬低它呢？不知道脾胃之气太弱时，必须用山药来健运它；但如果脾胃之气已经太旺，还使用山药，就会过于强旺，反而引动火邪。世人往往有胸腹饱闷的症状，服用山药后反而更严重，这正是助长了脾胃的旺盛之气。人们不知道这是山药的过错，而归咎于其他药物，这都是不明白药性原理的缘故。大概山药入心，会引导脾胃的邪气也容易进入心脏。山药补虚，但也能够补实，所以会导致饱闷感增加。因为世人都相信山药有功而无过，所以我特意指出这一点，并非贬低山药。除了这点之外，山药没有其他可议论的了。
有人问：山药是补阴精的药物，而您却说它是健脾胃的物品，为什么您喜欢标新立异呢？我说：山药对人益处无穷，损害人的情况极少。我谈论《本草》，是想让它的功与过都不被掩盖。山药有功而无过。说它能助长脾胃之火，这是在功劳中寻求过失罢了。然而天下人中脾胃太旺的，千人中只有一两个，不能执着于“动火”的说法，一概怀疑脾胃未旺的人也要慎用，如果脾胃未旺，肾气必然衰弱，健脾胃正是为了补阴精。我讲的是常理，有什么喜欢标新立异的呢？
有人问：山药补肾，张仲景公所以在六味地黄丸中使用它，然而山药确实能健脾开胃，难道六味丸不仅仅是补肾的药吗？我说：六味丸确实是直接补肾水的药物，山药也是补肾水的药物，同群共济有什么可疑的呢？然而，六味丸中使用山药，意义全不在于此。山药，是心、肝、脾、肺、肾五脏无经不进入的药物。六味丸虽然直接补肾中之水，但肾水必定分资于五脏，如果没有五脏相互引导的使者，又怎么由分布这些水，使它们无不滋润呢？倘若另外使用五脏的佐使之品，方剂必然杂乱而不纯粹，所以不如用山药来补肾中之水，而又可以遍通于五脏。这就是张仲景夫子补一顾五，实在有鬼神难测的机巧啊。（〔批注〕山药补水，而又通五脏，张仲景公所以在六味丸中使用它，自有这个方子，没有这个妙论。）
有人问：我已经听说了山药入六味丸的意义，不知道入八味丸中，也有说法吗？我说：八味丸，是由六味丸加增而成的，似乎知道六味丸，就可以知道八味丸的意义了。谁知八味丸中使用山药，又有别的妙义呢。六味丸，补肾中之水。而八味丸，则是补肾中之火。补肾中之火的，是补命门的相火。身体的相火有两个：一个在肾中，一个在心外。补肾中的相火，那么心外的相火，必然会来相争，相争则必相乱，应当预先有所安抚，势必在下补肾中的火，就应当在上面补心下的火。然而既然因为肾寒而补其下，又顾及心热以补其上，不用说下面不能温其寒，而且上面还会变为热了。用药的杂乱，可叹啊。妙在用山药于八味丸中，山药入肾占十分之七，入心占十分之三，引导桂枝、附子的热性，多在肾中温热，少在心外温热，使心肾二火各有相得，而不致相争，使肾的气通于心，而心的气通于肾，使脾胃之气安然健运不息，都是山药接引的功劳。张仲景公难道是随意使用的吗？（〔批注〕八味丸，补命门之火，补命门之火，考虑到心包之火必来相争，用山药解纷，使心肾相通、胃脾两健，哪里只是奇特而道理确实如此，真是张仲景公入室的高深用药啊。）
有人怀疑山药不宜多用。为什么六味地黄丸终年久服而没有害处呢？莫非入于地黄丸中可以多用，而入于其他药物之中就宜少用吗？不知道山药可以多用而没有禁忌。我前面说脾健之人宜忌，是担心助火以动燥，而不是说它不可以多用。
有人怀疑山药津液滑利，怎么能动燥呢？我说：山药生精，自然不是助燥之物。我说它助燥，是助长有火之人的燥，不是助长无火之人的燥。
有人问：山药颜色白，怎么能乌须发呢？为什么我用它作为乌须发的圣药？我说：山药怎么能乌须发呢。山药入肾，而且特别通任脉和督脉。任督之脉，上行于唇颊，所以借山药用在黑芝麻、黑豆、地黄、南烛、何首乌之内，引导以使须鬓变黑，不是山药自己能变黑的。有人又问：山药既然是引导之药，就不宜重用为君药了。不知道山药虽然不变白，但其性功确实是大补肾水的。肾水不足的人，须鬓绝对不能黑，我所以重用山药而奏效。
Chinese Yam (Dioscoreae Rhizoma), sweet in flavor, neutral in temperature, non-toxic. It enters the Taiyin organs of the hand and foot meridians (Lung and Spleen), and can also enter the Spleen and Stomach. It treats various deficiencies and hundred damages, benefits Qi and strength, opens the orifices of the Heart, enhances wisdom, and is particularly good at stopping nocturnal emissions, strengthening the Spleen, promoting appetite, stopping diarrhea, and generating essence. Chinese Yam can serve as either a sovereign drug or an assistant drug; there is no unsuitable use for it. Using more yields benefits, using less also yields benefits, and since ancient times to the present, there has been little dissent. However, I alone have slight reservations because it overly strengthens the Spleen. People suffer from weak Spleen function; if the Spleen is strengthened, the Large Intestine will surely become firm, and Stomach Qi will surely become strong with good appetite. Why single it out for criticism? One must not realize that when Spleen and Stomach Qi are too weak, Chinese Yam must be used to strengthen them; but if Spleen and Stomach Qi are already too vigorous, using Chinese Yam will make them excessively strong, potentially stirring up Fire. Often, people experience chest and abdominal fullness and distension, which worsens after taking Chinese Yam; this is precisely because it aids the excessive vigor of the Spleen and Stomach. People do not know this is the fault of Chinese Yam but blame other herbs; this stems from a lack of understanding of the principles of herb properties. Generally, Chinese Yam enters the Heart, guiding pathogenic factors from the Spleen and Stomach to easily enter the Heart. Chinese Yam tonifies deficiency but can also tonify excess, thus causing increased fullness and distension. Since the world believes Chinese Yam has merits without faults, I point this out specifically, not to disparage Chinese Yam. Apart from this, there is nothing else to discuss regarding Chinese Yam.
One asks: Chinese Yam is a substance that tonifies Yin and Essence, yet you say it is a product for strengthening the Spleen and Stomach. Why do you like to be different? I reply: Chinese Yam benefits people infinitely, and harms them rarely. When discussing Materia Medica, I wish for its merits and faults not to obscure each other. Chinese Yam has merits without faults. To say it can aid Spleen and Stomach Fire is seeking faults within its merits. However, among all people, those with overly vigorous Spleen and Stomach are one or two in a thousand. One cannot cling to the theory of "stirring Fire" and generally suspect that those with unvigorous Spleen and Stomach should also use it cautiously. If Spleen and Stomach are unvigorous, Kidney Qi must be weak; strengthening the Spleen and Stomach is precisely how one tonifies Yin and Essence. I speak of the general rule; what is there to be different about?
One asks: Chinese Yam tonifies the Kidney, which is why Master Zhang Zhongjing used it in Liuwei Dihuang Wan (Six-Ingredient Pill with Rehmannia). However, Chinese Yam truly can strengthen the Spleen and promote appetite. Is Liuwei Dihuang Wan not solely a medicine for tonifying the Kidney? I reply: Liuwei Dihuang Wan is indeed a medicine that directly tonifies Kidney Water. Chinese Yam is also a medicine that tonifies Kidney Water. How can there be doubt in their mutual assistance? However, the meaning of using Chinese Yam in Liuwei Dihuang Wan lies entirely elsewhere. Chinese Yam is a herb that enters no meridian without entering the Heart, Liver, Spleen, Lung, and Kidney. Although Liuwei Dihuang Wan directly tonifies Water in the Kidney, Kidney Water must be shared by the Five Zang Organs. Without guides to lead between the Five Zang Organs, how can the water be distributed to moisten them all? If one were to use separate assistant drugs for the Five Zang Organs, the formula would inevitably be mixed and impure. Therefore, it is better to use Chinese Yam to tonify Water in the Kidney while simultaneously penetrating all Five Zang Organs. This is Zhang Zhongjing’s strategy of tonifying one while attending to five, possessing a mechanism difficult to fathom even by spirits. ([Commentary] Chinese Yam tonifies Water and penetrates the Five Zang Organs. Master Zhang Zhongjing’s use of it in Liuwei Dihuang Wan relies on this prescription, lacking this profound discussion.)
One asks: I have heard the meaning of Chinese Yam entering Liuwei Dihuang Wan. Is there also a rationale for its entry into Bawei Wan (Eight-Ingredient Pill)? I reply: Bawei Wan is an augmentation of Liuwei Dihuang Wan. It seems that knowing Liuwei Dihuang Wan allows one to know the meaning of Bawei Wan. Who would expect that the use of Chinese Yam in Bawei Wan holds another profound meaning? Liuwei Dihuang Wan tonifies Water in the Kidney. Bawei Wan, however, tonifies Fire in the Kidney. Tonifying Fire in the Kidney means tonifying the Ministerial Fire of the Mingmen (Gate of Life). There are two Ministerial Fires in the body: one in the Kidney, one outside the Heart. If one tonifies the Ministerial Fire in the Kidney, the Ministerial Fire outside the Heart will inevitably contend. Contention leads to chaos; thus, one must prepare to pacify it. If one tonifies Fire below, one must also tonify Fire above (in the Heart). However, if one tonifies below due to Cold in the Kidney, and attends to Heat in the Heart by tonifying above, let alone failing to warm the Cold below, the above may turn into Heat. The complexity of medication usage is lamentable. The brilliance lies in using Chinese Yam in Bawei Wan. Chinese Yam enters the Kidney 70% and the Heart 30%. It guides the heat of Cinnamon Twig (Guizhi) and Aconite Root (Fuzi) to warm mostly in the Kidney and slightly outside the Heart. This ensures the Heart and Kidney Fires coexist harmoniously without contention, allowing Kidney Qi to connect with Heart Qi and Heart Qi to connect with Kidney Qi, enabling the Spleen and Stomach Qi to operate smoothly and ceaselessly. All this is due to the guiding merit of Chinese Yam. Did Master Zhang Zhongjing use it arbitrarily? ([Commentary] Bawei Wan tonifies the Fire of the Mingmen. When tonifying the Fire of the Mingmen, one worries that the Fire of the Pericardium will contend. Using Chinese Yam to resolve discord makes Heart and Kidney communicate, and Stomach and Spleen healthy. Not only is it unique, but the principle is so accurate; it is truly a profound herb of Master Zhang Zhongjing.)
Some suspect Chinese Yam should not be used in large doses. Why is there no harm in taking Liuwei Dihuang Wan for years? Could it be that it can be used in large doses when entering Dihuang Wan, but should be used in small doses when entering other formulas? One does not know that Chinese Yam can be used in large doses without taboo. What I previously said about avoiding it for those with strong Spleen was to worry about aiding Fire and stirring Dryness, not saying it cannot be used in large doses.
Some suspect Chinese Yam is slippery and moist, how can it stir Dryness? I reply: Chinese Yam generates Essence; naturally, it is not a substance that aids Dryness. When I say it aids Dryness, I mean it aids those who already have Fire, not those without Fire.
One asks: Chinese Yam is white in color, how can it darken beard hair? Why do I use it as the supreme herb for darkening beard hair? I reply: How can Chinese Yam darken beard hair? Chinese Yam enters the Kidney and particularly connects the Ren Mai (Conception Vessel) and Du Mai (Governing Vessel). The Ren and Du vessels ascend to the lips and cheeks. Therefore, borrowing Chinese Yam to be used within Black Sesame, Black Bean, Rehmannia Root (Shengdi Huang), Myrica Rubra Fruit (Nanzhu), and Polygonum Multiflorum Root (Heshouwu) guides the process to blacken the beard and temples. It is not that Chinese Yam itself turns black. One might ask again: If Chinese Yam is a guiding herb, it should not be heavily used as a sovereign drug. One does not know that although Chinese Yam does not change color, its nature and function truly greatly tonify Kidney Water. Those with insufficient Kidney Water absolutely cannot have black hair/temples. This is why I heavily use Chinese Yam to achieve efficacy.