It refers to the dried rhizome of Dioscorea Hypoglauca Palibin or Dioscorea Septemlobus Thumb., which are creeping perennial herbs. The slices of the former, Fen Bei Xie, are 1 to 3mm thick, ragged edges, or with brownish black rind, yellowish white, fine and smooth, and powdery and irregular yellow vein pattern. Quality is solid and elastic but easily broken. The preferred one medicinally is dried trunk, yellowish white in color, big and thin slices, good elasticity, consistency, and integrity. It is mainly produced in Zhejiang, Guangdong, and Guangxi provinces;

The round slices of latter, Mian Bi Xie, are cut lengthways or crosswise, in different sizes, about 2 to 3mm thick. Grayish yellow cortex is thicker and the rim is mostly curly. Rough surface of the slices is light yellowish white and with veins. Quality is soft and easily broken. Medicinally the better one is dried trunk, white in color, and even thickness in slices. It is mainly produced in Zhejiang and Hubei provinces.

As one of primary traditional Chinese herbs for stranguria due to chyluria and cloudy urine by mixing semen in men, Bei Xie (dioscorea root) was rated especially high by Ben Cao Tong Xuan (The Mystery-penetrating Materia Medica). What's more, it's very versatile and even used externally for cures of skin disorders like eczema and pustular sores, which has been confirmed by antifungal effect of dioscin, newly found through modern medical experimental method.

Dioscorea Root

WHAT'S IT USED FOR? 
From the perspective of Traditional Chinese Medicine (TCM), it is neutral and bitter in nature and covers meridians of liver, stomach, and urinary bladder. Main functions are to promote diuresis to eliminate turbid and dispel pathogenic wind to dredge channel blockade. Main uses and indications are stranguria caused by chyluria, cloudy urine, heavy vaginal discharge, wind dampness, pain due to channel blockade, stiff joints, and knee and lower back pain. Usual dosage is 10 to 15 grams, in teapills (Wan) or powder (San).

RELATED HERBAL FORMULAS 
(1). Bei Xie Shen Shi Tang (Wan), from Yang Ke Xin De Ji (Collection of Personal Experiences Concerning Skin Lesions), by Gao Bing Jun, published 1805, is formulated mainly for ecthyma caused by dampness-heat diffused downward. Other herbal ingredients are Yi Yi Ren (Seeds of Job's Tears), Tu Fu Ling (Glabrous Greenbrier Rhizome), Hua Shi (Talcum Powder), Mu Dan Pi (Tree Peony Root Cortex), Ze Xie (Water Plantain), Tong Cao (Rice Paper Pith), and Huang Bai (Amur Cork Tree Bark);

(2). Bi Xie Fen Qing Yin (Wan and San), from Yang Shi Jia Cang Fang (Yang's Family Heritage Formulas), is designed primarily for warming kidney to promote diuresis and separating clear and excreting turbid. Main usage and indications are primordial Qi deficiency, stranguria and cloudy urine caused by deficient cold in lower jiao, frequent urination, turbid, white as rice-washed water, coagulate like paste, pale tongue with white coating, and deep pulse. Other herbs combined are Yi Zhi Ren (Black Cardamon), Shi Chang Pu (Sweetflag Rhizome), and Wu Yao (Lindera);

(3). Niu Xi Wan, from Sheng Ji Zong Lu (Complete Records of the Life Securing Classics), is largely made for deficient cold in small intestine and frequency of micturition. Other main medicinal herbs involved are Huai Niu Xi (Achyranthes), Xu Duan (Japanese Teasel Root), and Chuan Xiong (Szechuan Lovage).