黔产不及汉中者良。故称汉防己。其茎如葛蔓延。茎根甚嫩。折一头吹之。气从中贯
采其根用。剖开须作车辐解。而木强者不取也。汉防己。是根破之纹。作车辐解。黄实馨
木防己。是苗上有丁足子。青白虚软。（嘉谟）
气味大苦辛寒。性燥而不淳。善走下行。阴也。泄也。入足太阳经。防己阳中之阴药也。
（
脚
拘
己
凶突
热壅塞
气已亏
分湿热
致二阴不通者。
如肺痿咯血之类
防己于下部湿热药
乃无瞑眩之患。
主之。防己黄
风水恶风汗出。
甘草半两。锉散
痛加芍药。风湿
卫。防术胜食。
一钱。极验。
〔论〕防己为除下焦湿热要剂。何以能通十二经。以其为足太阳本经药。经固曰巨阳者。
诸
盖
病
亦可治
之为病
其义
之。
气郁
足肿一证。概以为湿热下溜耳。即是湿热概以为血分病耳。又不过曰气郁化湿。湿郁化
热耳
下输
后天
也。血海之上。乃有丹田。气充于血也。血生于气。则胃气之虚与胃阳之亢者。便
气海。使肺气下降入心而生血矣。不能生血。则
以冲任之气。不得胃气以行血海之化而达于足也
血困于湿。其热者阴气微也。湿热虽属血分之病。
乃先哲又谓胃气下陷者。盖天气下为雨。则地气上
升焉。（其举阴以上升者。乃阴中之阳。正谓元气
上升。（不能举阴以升。由冲任不得阳以化也。）
化以荣于周身。乃举身半以下为肿或痛矣。是其
必裕肾肝之阴以举阳。或益阳。或清其并阳之热
或升而举之。岂漫从事于祛除湿热。更加防己辈
阳以升。然后阳中含阴以降。此篇论病。乃先从
是病机之本也。其有肝肾阳微。阴不得化。而湿热只因于下者。又当从肝肾为本。第不能舍
后天生化之胃耳。
缪氏。防己性悍气猛。走窜决防。大苦大寒。能伤胃。凡胃虚阴虚肾虚小水不利。及胎
前产
〔辨治〕凡使。勿用木条色黄而腥皮皱上有丁足子。惟要心有花纹黄色者。去皮锉。酒
洗。
贵州出产的防己不如汉中出产的质量好，所以称为“汉防己”。它的茎像葛藤一样蔓延生长，茎和根都很嫩。折断一端吹气，气流能从中间贯通。采收其根部使用，剖开时须呈车辐状（车轮辐条）开裂，木质坚硬者不取。
汉防己的特征是根部剖开后纹理呈车辐状开裂。（黄实馨注）
木防己的特征是苗上有丁字形足状的果实，质地青白且虚软。（嘉谟注）
气味：大苦、辛，寒。
药性：性燥而不纯厚，善于走窜下行，属阴，主泄。入足太阳膀胱经。防己是阳中之阴的药。
（脚部拘挛、急迫、凶险突起、热邪壅塞、正气已亏、分清湿热导致二阴不通等证。）
如肺痿咯血之类病症，若用防己治疗下部湿热药物，则没有瞑眩反应的危险。主治风水恶风汗出，用防己黄芪汤（防己一两，甘草半两，锉散）。痛甚加芍药，风湿痹痛加桂枝以固卫。防己配伍白术可胜湿健脾。用量一钱，极有效验。
〔论〕防己是清除下焦湿热的要药，为什么能通利十二经？因为它是足太阳本经的药物。经文说巨阳者……盖病机之理在于此。
有人将足肿一症，一概认为是湿热下流；又有一概认为是血分病的；还有的不过说是气郁化湿，湿郁化热罢了。
其实，后天之气下输于肾，在血海之上，乃是丹田所在，气充养于血中。血生于气，如果胃气虚弱或胃阳亢盛，就会影响气海，使肺气不能下降入心而生血。如果不能生血，冲任之气就不能依靠胃气来行血海之变化并达于足部。
血困于湿，其热象是因为阴气微弱。湿热虽然属于血分的病，但先哲又说这是胃气下陷所致。正如天气下降为雨，地气才能上升。（那些能够举阴以上升的，乃是阴中之阳，正指的是元气上升，不能举阴以升，是因为冲任得不到阳气来化生。）
阳气化生以荣养周身，于是出现半身以下肿胀或疼痛。这是病机的根本。必须充裕肾肝之阴以举阳，或者益阳，或者清其并行之阳的热邪，或者升提举之。难道可以漫无目的地从事于祛除湿热，再加上防己这类药物吗？只有阳气上升，然后阳中含阴以降，这才是病机之本。
如果有肝肾阳微，阴不得化，而湿热只因于下部的，又应当从肝肾为本，只是不能舍弃后天生化的脾胃罢了。
The Fangji (Stephaniae Tetrandrae Radix) produced in Guizhou is not as good as that from Hanzhong, hence it is called "Han Fangji" (Fangji from Hanzhong). Its stems creep like those of Puerariae Lobatae Radix (Kudzu Root). The stems and roots are very tender; if one end is broken and blown into, the air passes through the center. The roots are harvested for use. When sliced, they must split radially like the spokes of a wheel; those with hard wood are not selected.
The characteristic of Han Fangji is that the root splits radially like wheel spokes when剖开 (split open). (Note by Huang Shixin)
The characteristic of Mu Fangji (Stephaniae Membranaceae Radix) is that there are horned fruits on the seedlings, with a bluish-white, hollow, and soft texture. (Note by Jiamo)
Flavor and Nature: Greatly bitter, acrid, cold.
Properties: It is drying but not pure or mellow, excels at moving downward, belongs to Yin, and has a draining action. It enters the Foot-Taiyang Bladder Meridian. Fangji is a medicine of Yin within Yang.
(Indications include foot cramps, urgency, severe protrusions, heat obstruction, deficiency of healthy Qi, differentiation of damp-heat leading to blockage of the two yin orifices.)
For conditions such as Fei Wei (Lung Withering) with hemoptysis, if Fangji is used in formulas for lower jiao damp-heat, there will be no risk of Mingxuan reaction (severe adverse reaction followed by improvement). It treats Feng Shui (Wind-Water edema) with aversion to wind and sweating. Formula: Fangji Huangqi Tang (Huangqi Decoction with Fangji), consisting of Fangji (1 liang) and Gancao (Licorice Root, 0.5 liang), crushed into powder. If pain is severe, add Shaoyao (Peony Root); for Wind-Damp Bi syndrome, add Guizhi (Cinnamon Twig) to secure the Defensive Qi. Fangji combined with Baizhu (Atractylodis Macrocephalae Rhizoma) can overcome dampness and strengthen the Spleen. Dosage: 1 qian, which is highly effective.
[Discussion] Fangji is an essential herb for clearing damp-heat from the Lower Jiao. Why can it unblock the Twelve Meridians? Because it is a primary herb of the Foot-Taiyang Meridian itself. The Classics state that Ju Yang (Giant Yang)... covers the pathology.
Some regard foot swelling solely as damp-heat flowing downward; others attribute it entirely to Blood-level pathology; still others merely say it is Qi stagnation transforming into dampness, and dampness transforming into heat.
In reality, Postnatal Qi descends to the Kidney. Above the Sea of Blood lies the Dantian, where Qi nourishes Blood. Blood is generated from Qi. If Stomach Qi is deficient or Stomach Yang is hyperactive, it affects the Sea of Qi, preventing Lung Qi from descending into the Heart to generate Blood. If Blood cannot be generated, the Chong and Ren vessels cannot rely on Stomach Qi to transform the Sea of Blood and reach the feet.
Blood trapped by dampness manifests as heat due to slight Yin Qi. Although damp-heat belongs to Blood-level pathology, ancient sages also stated this is caused by sinking of Stomach Qi. Just as Heaven's Qi descends as rain, Earth's Qi rises. (Those that lift Yin upward are Yang within Yin, referring to Yuan Qi ascending. Failure to lift Yin is because Chong and Ren lack Yang to transform.)
Yang Qi transforms to nourish the whole body; thus, swelling or pain occurs below half the body. This is the root of the pathogenesis. One must enrich Kidney and Liver Yin to lift Yang, or tonify Yang, or clear the heat of concurrent Yang, or ascend and lift it. How can one blindly engage in dispelling damp-heat and adding herbs like Fangji? Only when Yang ascends can Yin descend contained within Yang. This is the root of pathogenesis.
If there is slight Yang of Liver and Kidney, Yin fails to transform, and damp-heat arises only from below, treatment should target Liver and Kidney as the root, yet one cannot abandon the Postnatal transformation of the Stomach.
Miu states: Fangji is fierce in nature and vigorous in Qi, moving freely and draining severely. Being greatly bitter and cold, it can damage Stomach Qi. It is contraindicated in cases of Stomach deficiency, Yin deficiency, Kidney deficiency with difficult urination, and during pregnancy or postpartum...
[Differentiation and Treatment] When using Fangji, do not use the variety with yellow, fishy-smelling stems, wrinkled skin, and horned fruits (which is Mu Fangji). Select only the variety with radial patterns inside and yellow color. Remove the bark, crush, and wash with wine.