防己之根，外白内黄，有黑纹如车辐解，气味辛平，故治由肾以抵脾肺风湿之 。肺主
皮毛，将毋从皮毛而散乎？然车能环转不能外溢，故防己绝不发汗而第直泄于小便。如金匮
己椒苈黄丸（义见大黄），千金三物木防己汤可按也。
陶隐居云∶防己是疗风水要药。水与饮皆湿类也，故防己黄 汤治风湿，防己茯苓汤治
水，木防己汤治饮，名虽有三，理无少异。惟风水二字，诚有不得而析者，风阳邪而风从外
入，令人振寒，风寒初受，即宜汗解，防己非其责也。内伏之风，若内无阴邪，亦未能独存，
故水饮湿悉其所因依，水饮湿去，则风与俱去。如此之风，方可治以防己。然苓术不能而防
己独能之者，以黑纹如车辐解，正有风水相随之妙致也。
或云∶防己地黄汤，治病如狂状妄行，独语不休，无寒热，其脉浮，岂亦有水饮湿也，
而顾以防己治耶？曰∶此仲圣别出手眼之方，未可与他并论者也。赵氏谓血虚从邪，邪并于
阳而然。按本篇固以脉浮为血虚，素问阴不胜其阳则脉流薄疾并乃狂，固可为如狂之据，此
注允矣。而不言邪为何邪。徐氏则谓风邪并入于心，心火炽盛，故如狂妄行，独语不休，较
赵注为明晰矣。而于是方用药之所以然，则皆未发出。窃细玩之，四物酒渍取汁，自非阳邪
表邪不尔。生地黄独多，自非补血凉血不尔。有表邪而用桂枝防风，可知是外入之风邪。以
生地黄偶桂枝防风，可知治不以汗解。不以汗解而有酒行药势以搜之，则邪不至或遗。四物
取生汁而地黄取蒸汁，则阴阳得以分理，既所以退阳而安阴矣。然而风无出路，则风仍不息。
阴不复位，则阴仍羁阳。欲并者而使之分，仲圣所以有取于防己也。夫防己者，走表而亦下
行者也。操运转之技，则表间之风自随之得息。具返本之能，则被扰之阴亦因之得静。或谓
防己治风湿不治风燥，不知风药中用地黄至数倍，则风亦转燥为润，正与防己相宜，可谓以
人巧夺天工矣。
防己的根，外部白色内部黄色，有黑色的纹路像车轮的辐条一样散开，气味辛平，所以能治疗由肾脏波及脾肺的风湿之邪。肺主皮毛，难道不是从皮毛而发散吗？然而车轮只能环转滚动而不能向外溢出，所以防己绝不发汗，只是直接通过小便泄出。可以参考《金匮要略》中的己椒苈黄丸（含义见大黄条），以及《千金方》中的三物木防己汤。
陶弘景说：防己是治疗风水病的要药。水邪和饮邪都属于湿类，所以防己黄芪汤治疗风湿，防己茯苓汤治疗水气，木防己汤治疗饮邪，名称虽然有三个，但道理没有多少差异。只是“风水”这两个字，确实有难以剖析清楚的地方。风为阳邪，且风从外侵入，使人战栗恶寒，风寒初受之时，应当用发汗法解表，防己并不承担这个责任。内伏的风邪，如果体内没有阴邪作为依附，也不能单独存在，所以水、饮、湿都依赖某种基础，水饮湿去除后，风邪也就随之而去。这样的风邪，才可以用来防己治疗。然而白术、茯苓不能做到这一点而防己却能做到的原因，是因为其黑纹像车轮辐条散开，正具有风水相随的微妙机理。
有人说：防己地黄汤，治疗像发狂一样的症状，胡乱行走，独自说话不停，没有寒热表现，脉象浮，这难道也有水饮湿邪吗，却反而用防己来治疗呢？回答说：这是张仲景别具匠心的方剂，不可以和其他方子并列讨论。赵氏认为血虚导致邪气入侵，邪气并入阳分而致病。按本篇原文确实以脉浮为血虚的依据，《素问》说阴不能胜阳则血脉流动急迫，进而发狂，这确实可以作为如狂症状的依据，这个注释很妥当。但没有说明邪气是什么邪气。徐氏则认为风邪并入于心，心火炽盛，所以出现如狂、妄行、独语不休的症状，比赵注更为明晰。但是对于该方用药的原理，都没有揭示出来。我仔细玩味此方，四物汤用酒浸泡取汁，如果不是因为阳邪或表邪不会这样。生地黄用量最多，如果不是为了补血凉血不会这样。有表邪而使用桂枝、防风，可知是外入的风邪。将生地黄与桂枝、防风配合使用，可知治疗不以发汗解表为主。不以发汗解表而用酒来运行药势以搜剔邪气，那么邪气就不会被遗漏。四物汤取生汁而地黄取蒸汁，则阴阳得以分别调理，这就是为了退阳而安阴的方法。然而风邪如果没有出路，风邪就不会停止。阴气如果不能复位，阴气就会羁留阳气。想要使相并的邪气分离，这就是张仲景选用防己的原因。防己，既能走表又能下行。具备运转的技能，则体表的風邪自然随之平息。具备返本的能力，则被扰动的阴气也因此得以安静。有人说防己治疗风湿不治疗风燥，不知道在风药中加入数倍的地黄，则风邪也会转为燥变为润，正与防己相适宜，可以说是以人工巧夺天工了。
The root of *Stephaniae Tetrandrae Radix* (Fangji) is white on the outside and yellow on the inside, with black striations resembling the spokes of a wheel radiating outward. Its flavor is pungent and neutral; therefore, it treats wind-dampness pathogens that travel from the Kidney to involve the Spleen and Lungs. The Lung governs the skin and hair; does not the pathogen disperse through the skin and hair? However, just as a wheel rotates in circles but does not overflow outward, *Stephaniae Tetrandrae Radix* never induces sweating but rather drains directly through urination. This can be verified by referring to *Jingui Yaolue*'s *Ji Jiao Li Huang Wan* (meaning see *Rhei Radix et Rhizoma*) and *Qianjin Fang*'s *Sanwu Mufangji Tang*.
Tao Hongjing stated: "*Stephaniae Tetrandrae Radix*" is an essential herb for treating Wind-Water edema. Water retention and Phlegm-Fluid are both categories of Dampness; thus, *Atractylodis Macrocephalae Radix* and *Stephaniae Tetrandrae Radix* Decoction (*Fangji Huangqi Tang*) treats Wind-Dampness, *Stephaniae Tetrandrae Radix* and Poria Decoction (*Fangji Fuling Tang*) treats Water-Qi, and *Bitter Orange, Stepahaniae Tetrandrae Radix* and Ginseng Decoction (*Mufangji Tang*) treats Phlegm-Fluid. Although the names differ, the underlying principles are largely identical. However, the term "Wind-Water" is indeed difficult to dissect precisely. Wind is a Yang pathogen entering from the exterior, causing chills and tremors; when Wind-Cold is initially contracted, diaphoresis (sweating) should be employed to resolve the exterior, a task for which *Stephaniae Tetrandrae Radix* is not responsible. Internal latent Wind cannot persist alone without Yin pathogens as its foundation; thus, Water, Phlegm-Fluid, and Dampness rely on specific dependencies. Once Water, Phlegm-Fluid, and Dampness are eliminated, Wind departs with them. Only such Wind can be treated with *Stephaniae Tetrandrae Radix*. The reason why *Atractylodis Macrocephalae Radix* and Poria cannot achieve this while *Stephaniae Tetrandrae Radix* can lies in its black striations resembling radiating wheel spokes, embodying the subtle mechanism of Wind accompanying Water.
Some ask: *Stephaniae Tetrandrae Radix* and Rehmannia Decoction (*Fangji Dihuang Tang*) treats conditions presenting as mania-like states, aimless walking, continuous solitary speech, without chills or fever, and with a floating pulse. Does this also involve Water, Phlegm-Fluid, or Dampness, warranting the use of *Stephaniae Tetrandrae Radix*? I reply: This is a unique prescription by Zhang Zhongjing, not to be compared with others. Zhao believed that Blood deficiency allows pathogens to invade, merging into the Yang level. The text indeed cites the floating pulse as evidence of Blood deficiency; *Suwen* states that if Yin cannot overcome Yang, the pulses flow rapidly, leading to mania, which supports the diagnosis of mania-like symptoms. This annotation is sound but fails to specify the nature of the pathogen. Xu argued that Wind-pathogen merges into the Heart, causing blazing Heart-Fire, resulting in mania, aimless walking, and continuous speech, which is clearer than Zhao's note. However, neither explains the rationale behind the herbal composition. Upon careful study: Soaking the Four Substances (*Sìwù*) in wine to extract juice implies the presence of Yang or Exterior pathogens. The predominant use of Prepared Rehmannia Root (*Shu Dihuang*) or Raw Rehmannia Root (*Sheng Dihuang*) indicates the intent to nourish Blood and cool Blood. The inclusion of Cinnamon Twig (*Guizhi*) and Saposhnikovia Root (*Fangfeng*) alongside these confirms an external Wind-pathogen. Combining Rehmannia with Cinnamon Twig and Saposhnikovia indicates treatment is not aimed at inducing sweating. Since sweating is not the method, wine is used to circulate the medicinal power to search out pathogens, ensuring none are left behind. Extracting juice from raw herbs versus steamed Rehmannia allows for the distinct regulation of Yin and Yang, thereby subduing Yang and calming Yin. However, if Wind has no exit, it will not cease; if Yin does not return to its proper position, it will constrain Yang. To separate what has merged, Zhang Zhongjing utilized *Stephaniae Tetrandrae Radix*. *Stephaniae Tetrandrae Radix* travels to the exterior and descends internally. With its rotating capability, Wind in the exterior naturally subsides. With its ability to restore origin, disturbed Yin becomes tranquil. Some claim *Stephaniae Tetrandrae Radix* treats Wind-Dampness but not Wind-Dryness. They fail to realize that adding Rehmannia in multiples within Wind-dispersing herbs transforms Wind-Dryness into Moisture, perfectly complementing *Stephaniae Tetrandrae Radix*, achieving a skill that rivals nature itself.