Rhizoma Dioscoreae (Shan Yao or Chinese Yam). The Rhizome of the perennial herbaceous trailing plant Dioscorea Opposita Thunb. of the family Diosoreaceae.
The plant from which these chalk-white slivers are produced grow in Korea and China, and also in the Chinese provinces of Henan and Hunan. They are believed to be a tonic for the kidneys and lungs, and are prescribed for diarrhoea, diabetes and urinary problems. It is sometimes referred to as huai shan in Mandarin, which corresponds with the common Cantonese name of wai san, because the huaishan region in China is believed to produce the best the its kind.