鲜者。羊之气也。此草根皮白色。作膻气。二月采者根心实。若四五月采。便虚恶。
根皮味微咸。辛而苦。气寒性燥。降多于升。手足太阴经去湿热药也。兼入手太阳阳明。
为诸黄风痹要药。膻者肝之臭。当入肝。为肝之用药。从治风气者也。亦复入脾除湿。（复）
主治通关节。利九窍及血脉。疗一切热毒风恶风。及湿痹死肌。不可屈伸。起止行步。治黄
疸。兼女子阴中肿痛。外治毒风癣疮。眉发脱落。（诸本草）方书治消瘅。中风香港脚。目外
障。鼻舌。得苍术黄柏牛膝石斛薏苡。疗足弱顽痹。去下部湿热。多加金银花。佐以汉防己。
治下部一切湿疮。准绳治心脏中风。恍惚恐惧。闷乱语错。不卧。牛黄散方中用白藓皮。由
母以病子也。
〔论〕 白藓皮味始微咸。后微辛。后即纯苦。苦中复有微辛。本草言其气寒。夫咸应
入血。今苦寒之性。合之以辛而入血。宜能清散血中之滞热矣。经曰。肝臭臊。白藓皮之臭
绝膻。当是木气。且肝为藏血之脏。又为风脏。不独血虚能生风。即血滞者亦然。血之滞也。
不
观于采根以二月。入夏则虚恶。洵当专禀风木之用。而膻臭触人。又其根皮色白。木固藉金
气以达者。卢氏曰。脾以肝为用。亦可除湿。此之藉金气以达者。肝更藉肺为用。以致于脾
。脾因肝之血和。肺之气达。而湿热乃散。（如阴中肿痛及筋病不可屈伸。此肝病也。如黄
疸湿痹死肌。此脾与肺之病也。）大抵肝肾居下。其奏功虽多在下部。然未有脾肺之气不达
而能疗者也。
缪氏云。下部虚寒之人。虽有湿证。弗用。
〔修治〕 水洗。去粗皮。
Fresh Bai Xian Pi (Dermatophyllum Root Bark) possesses the odor of mutton. The root and bark of this plant are white in color and emit a musky, sheep-like odor. Those harvested in the second lunar month have solid root centers; whereas those harvested in the fourth or fifth months are hollow and inferior in quality.
The root bark tastes slightly salty, pungent, and bitter. Its nature is cold and dry, with descending actions predominating over ascending ones. It is a herb that clears damp-heat from the Hand and Foot Taiyin meridians, and also enters the Hand Taiyang and Hand Yangming meridians.
It is a crucial herb for treating various types of jaundice and wind-bi syndrome. The musky odor corresponds to the smell associated with the Liver; therefore, Bai Xian Pi enters the Liver and serves as an agent for regulating Liver Qi, employing the method of "conforming treatment" (treating wind by following its nature). It also enters the Spleen to remove dampness.
Its primary indications include unblocking joints, benefiting the nine orifices and blood vessels, and treating all forms of heat-toxic wind, aversion to wind, and wet-bi syndrome causing muscle atrophy, joint immobility, and difficulty in walking. It treats jaundice and concurrently addresses swelling and pain in the female genitalia. Externally, it treats toxic wind tinea and alopecia (loss of eyebrows and hair). (According to various Materia Medica texts.) Formulary books indicate its use for Xiao Dan (wasting-thirst/diabetes), stroke, Hong Jiao (gout/foot disease), external cataracts, and nasal/tongue disorders. When combined with Cang Zhu (Atractylodis Rhizoma), Huang Bo (Phellodendri Cortex), Niu Xi (Achyranthis Bidentatae Radix), Shi Hu (Dendrobii Caulis), and Yi Yi Ren (Coicis Semen), it treats lower limb weakness and stubborn bi-syndrome, clearing damp-heat from the lower jiao. With the addition of Jin Yin Hua (Lonicerae Japonicae Flos) and support from Han Fang Ji (Stephaniae Tetrandrae Radix), it treats all damp-sores in the lower body. *Zhun Sheng* records its use for Heart Wind-Stroke, manifesting as mental confusion, fear, restlessness, disordered speech, and insomnia. In the Niu Huang San (Calculus Bovis Powder) formula, Bai Xian Pi is used due to the transmission of disease from mother to child (Liver transmitting to Heart).
[Discussion] The taste of Bai Xian Pi begins as slightly salty, becomes slightly pungent, and then turns purely bitter, with a hint of pungency within the bitterness. Materia Medica states its nature is cold. Since salty flavors enter the Blood level, its bitter-cold nature combined with pungency allows it to enter the Blood, thereby likely clearing and dispersing stagnant heat within the Blood. The Classics state: "The Liver's odor is musky/su." The strong musky odor of Bai Xian Pi aligns with the Wood element (Liver belongs to Wood). Furthermore, the Liver stores Blood and is the organ of Wind; not only can Blood deficiency generate Wind, but Blood stasis can also do so. Observing that the roots are harvested in the second month and become hollow and inferior in summer confirms that it exclusively inherits the function of Wind-Wood Qi. The pungent odor touching the nose, along with the white color of the root bark, suggests that Wood Qi relies on Metal Qi (Lung belongs to Metal, color white) to achieve penetration. Mr. Lu stated: "The Spleen utilizes the Liver, thus it can also remove dampness." Here, relying on Metal Qi to penetrate refers to the Liver utilizing the Lung to affect the Spleen. Because the Spleen benefits from the harmonization of Liver Blood and the dissemination of Lung Qi, damp-heat is dispersed. (For instance, swelling/pain in the genitalia and inability to flex/extend tendons are Liver diseases; jaundice, wet-bi, and muscle atrophy are Spleen and Lung diseases.) Generally, the Liver and Kidney reside in the lower jiao, and although their efficacy often manifests in the lower body, there is no cure without the Qi of the Spleen and Lung reaching the affected area.
Mr. Miao stated: For individuals with deficiency-cold in the lower jiao, even if dampness syndromes are present, Bai Xian Pi should not be used.
[Processing] Wash with water and remove the coarse outer skin.