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Gancao (Radix Glycyrrhizae), grows in the Jiashan Valley of Hexi and Shangjun; currently, it is produced in various prefectures of Shaanxi and Hedong. In spring, green shoots emerge, one to two chi high; the leaves resemble those of the locust tree; in July, purple flowers bloom, resembling Naiguo (a type of fruit); in winter, it bears fruits that form pod-like beans similar to Bidou. The roots are three to four chi long, varying in thickness, with a reddish skin and horizontal ridges above, beneath which lie fine lateral roots. The roots are harvested on the "Chu" day in February and August, then sun-dried; after ten days, the rhizomes and red skins are removed, though currently it is said to be used after shade-drying.

There are several varieties of Gancao today; those that are solid and have clear fracture lines are considered superior. Those that are light, spongy, longitudinally fibrous, and thin/tough are unsuitable for primary use and are only sold to decoction makers. According to the *Erya*: "[Name], Daku." The commentary states: "[Name], also known as Daku. Dunpu says: This is Gancao, growing creeping, with leaves resembling lotus leaves, yellow-green in color, stems are red with nodes, and branches grow opposite at the nodes. Some say it resembles Dihuang (Radix Rehmanniae). The *Book of Songs · Tang Feng* says: 'Gather Ling, gather Ling, on the peak of Shouyang,' referring to this plant. "[Name]" and "Ling" are used interchangeably. Mount Shouyang is in Pu County, Hedong, near where Gancao currently grows, yet the description of its seedlings and leaves by ancient scholars differs completely from today's; could there be different species?

Zhang Zhongjing's *Shanghan Lun* contains formulas such as Yiwu Gancao Tang (Single-Ingredient Licorice Decoction), Gancao Fuzi Tang (Licorice and Aconite Decoction), Gancao Jiangxin Tang (Licorice and Dried Ginger Decoction), and Gancao Xiexin Tang (Licorice Drain the Epigastrium Decoction). Among these formulas, Gancao is used most frequently; it can also detoxify hundred poisons and serves as a key herb among many medicines. Sun Simiao discussed: If someone is poisoned by Wutou (Radix Aconiti) or Badou (Semen Crotonis), Gancao settles the poison upon entering the abdomen. Formulas claim that Dadou (Soybean) can detoxify hundred medicines, but attempts proved ineffective; thus, adding Gancao to create Gandou Tang (Sweet Bean Decoction) yielded faster results. Additionally, the *Beiji Fang* records: Cishi Bian once stated that the Liren people in Lingnan use antidotes that are common food items. Fearing others would learn the method, they called it "Three Hundred Oxen Medicine" or "Three Hundred Taels Silver Medicine." Bian lived there for a long time and befriended them, eventually learning the truth. Before eating, one should take one cun of Gancao, roast it, chew it, and swallow the juice. If poisoned, vomiting occurs immediately; then, using Duteng and Huangteng, decocted in warm wine, toxins are expelled through urination and defecation. Duteng originates from Lingnan, over three chi high, very slender, known as the "Three Hundred Taels Silver Medicine." One should always carry several cun of Gancao for emergencies. If food is not vomited after holding Gancao in the mouth, it is not poison.

Cui Yuanliang's *Haishang Fang*, a secret method for treating Fabei (Back Carbuncle): Li Beihai said, "This formula was divinely revealed, extremely rare and secret." Use three da liang of Gancao, crush raw, sift into powder separately; mix with nine liang of Da Mai Mian (Barley Flour) in a large plate until uniform. Add a small amount of high-quality Su (Butter/Ghee), knead into the medicine until uniform. Knead with boiling water into cake-sized doughs, slightly larger than the wound. Apply hot compresses to the swelling, separating with oil paper and old paper to allow ventilation; replace when cold. If pus has formed, it will drain naturally; if not, the swelling dissipates internally. While applying the medicine to the swelling, consuming Huang Mi Zhou (Yellow Millet Porridge) is excellent. Another method: Roast one da liang of Gancao slightly, crush, soak in one sheng of water overnight outdoors in the open air. At dawn, stir with an object to produce foam, blow off the foam, and consume. This is effective for all sores, swellings, and Fabei.