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[Shanyao (Dioscoreae Rhizoma)]
The thermal nature is warm, the flavor is sweet and neutral. It is non-toxic.
It enters the Hand-Taiyin Lung Meridian.
Bencao states: Its main functions are tonifying the middle and boosting Qi, clearing heat, and strengthening Yin. It treats wandering wind on the head and face, and dizziness caused by wind. It directs Qi downward, replenishes the five Zang organs, promotes muscle growth, and with long-term use, improves hearing and vision, lightens the body, delays aging, extends life, and prevents hunger. As a drug for the Hand-Taiyin meridian, it moistens dry skin and hair; it is cooling yet tonifying. It acts as an assistant (Zhi Shi) when combined with Tianmendong (Asparagi Radix), Maidong (Ophiopogonis Radix), and Zizhi (Ganoderma). It is incompatible with Gansui (Kansui Radix).
Li Dongyuan said: Zhang Zhongjing used dried Shanyao in Bawei Wan (Eight-Ingredient Pill with Rehmannia) because it is cooling yet tonifying. It also treats dry skin by using its moisturizing properties.

[Bai Zhu (Atractylodis Macrocephalae Rhizoma)]
The flavor is sweet and neutral. It is non-toxic.
It enters the Foot-Taiyin Spleen Meridian and the Hand-Yangming Large Intestine Meridian.
Bencao states: Its main functions are tonifying the middle and boosting Qi, treating sweating due to stroke, expelling water, promoting urination, breaking up blood stasis, restoring blood vessels, and treating residual postpartum conditions in nursing mothers. It promotes hair growth and can be used as a shampooing agent. Long-term use makes the body robust and healthy, delaying aging.
Ye states: It enters the Foot-Taiyin Spleen and Hand-Yangming Large Intestine meridians. Excessive sweating, heatstroke, and difficult defecation all lead to fluid depletion, hence the term "Splee Constriction" (Pi Yue). "Yue" means constraint. The Neijing states: "Moisten what is dry." Therefore, Zhang Zhongjing used Mahuang Ren (Hemp Seed) to moisten the dryness of the Foot-Taiyin Spleen and unblock the intestines.

[Yi Yi Ren (Coicis Semen)]
The thermal nature is slightly cold, the flavor is sweet. It is non-toxic.
Bencao states: Its main functions are treating tendon spasms and contractures preventing flexion and extension, rheumatic bi-syndrome, and directing Qi downward. It eliminates pathogenic factors from bones and joints causing numbness, benefits the intestines and stomach, reduces edema, and stimulates appetite. With long-term use, it lightens the body and boosts Qi. Its root can expel three types of parasites. Zhang Zhongjing treated rheumatic pain that worsened at dusk (Ribu) using Mahuang Xingzi Yiyiren Tang (Ephedra, Apricot Kernel, and Coix Seed Decoction).

[Gan Cao (Glycyrrhizae Radix et Rhizoma)]
The thermal nature is neutral, the flavor is sweet, belonging to Yang. It is non-toxic.
It enters the Foot-Jueyin Liver Meridian, Foot-Taiyin Spleen Meridian, and Foot-Shaoyin Kidney Meridian.
Zhang Yuanjing said: Raw Gan Cao strongly clears fire and heat; roasted Gan Cao becomes warm and tonifies the Yuan Qi of the Upper, Middle, and Lower Jiao. It harmonizes various drugs, cooperating without conflict. Its nature is mild, and it is good at relieving various acute conditions, hence named "Guolao" (National Elder). Use the peeled root. Gan Cao Shao (the tip of the root), used raw as the chief ingredient, removes pain in the urethra; or combined with Kulian (Meliae Cortex) and Jiuzhu Xuyansuo (Vincae Rhizoma boiled in wine) as the chief ingredient, which is particularly effective.
Li Dongyuan said: When used with hot drugs, it moderates their heat; when used with cold drugs, it moderates their cold. The Classics state: "Sweetness moderates." For deficiency of Yang, tonify with sweetness, but avoid if there is fullness in the middle. It is used for both cold and heat patterns to harmonize drug properties and prevent incompatibility. Roasted Gan Cao disperses exterior cold, clears evil heat, relieves sore throat, clears heat, moderates Zheng Qi, moderates Yin Blood, and moistens the skin.
Wang Haogu said: It nourishes blood and tonifies the stomach. Gan Cao Shao removes pain in the kidneys. Accumulated heat in the chest cannot be cleared except by Gan Cao Shao.
Bencao states: It treats cold and heat pathogenic factors in the five Zang and six Fu organs, strengthens sinews and bones, promotes muscle growth, and increases strength. It treats metal wounds, detoxifies, warms the middle, and directs Qi downward. It treats irritability, distension, shortness of breath, and coughs due to organ damage. It stops thirst, unblocks meridians, benefits Qi and Blood, and resolves toxicity of hundred herbs. It is the essence of the nine soils, stabilizing and harmonizing seventy-two types of minerals and one thousand two hundred types of grasses, hence named Guolao.
Yaoxing Lun states: It serves as the Chief Drug. Avoid pork.
Neijing states: "The Spleen desires relaxation; urgently eat sweet things to relax it." Sweetness tonifies the Spleen and can relieve urgency, so it is used in decoctions to establish the Middle Jiao.
It also states: "Sweetness causes middle fullness." And: "Do not eat sweet things if you have middle fullness." Thus, it is known that Gan Cao is not specifically for treating fullness. Sweetness enters the Spleen and attacks where it is pleased.
Question: Both Fuzi Lizhong Tang and Tiaowei Chengqi Tang use Gan Cao. How does this reflect the meaning of harmonization?
Answer: In Fuzi Lizhong Tang, Gan Cao is used to prevent the rebellious ascent of other drugs; in Tiaowei Chengqi Tang, it is used to prevent rapid purgation. In these two formulas, Gan Cao is not used for harmonization but for moderation. In Xiaochaihu Tang, there is the cold of Chaihu and Huangqin, and the warmth of Renshen and Banxia; using Gan Cao here reflects true harmonization. If the middle is not full, using sweetness is for tonification; if the middle is full, using sweetness is for draining. This involves ascending, descending, floating, and sinking. The sweetness in Fengsui Dan moderates Kidney dampness to generate Yuan Qi, which is also the intent of sweet tonification. The Classics state: "Tonify with sweetness, drain with sweetness, moderate with sweetness." Bencao says: "Stabilize and harmonize seventy-two minerals and twelve hundred grasses," named Guolao. Although not the Chief Drug, it is revered by the Chief Drug, thus able to stabilize herbs and minerals and resolve various toxins. From this, we can see the meaning of harmonization. Regarding the use of the Five Flavors: Bitter goes straight down and drains; Pungent moves horizontally and disperses; Sour binds and converges; Salty stops and softens hardness; Sweet goes upward and disperses. How then does Bencao say it directs Qi downward? The nature of Sweetness has ascending/descending and floating/sinking qualities; it can go up or down, inside or outside; it has harmony and moderation, tonification and draining. The way of the center is complete. Entering the Foot-Jueyin, Taiyin, and Shaoyin meridians, it can treat pus and blood in Lung Wei (Flaccidity) as an emetic; it can eliminate sores and carbuncles of the five types. Boil three bowls of water slowly until half remains, remove dregs, and take. Its efficacy in eliminating sores is the same as Huangqi (Astragali Radix); Huangqi can also eliminate various swelling, toxic sores, and carbuncles. Its processing method is the same as Gan Cao.
Bencao further states: Baizhu, Ganzhi, and Kushen act as assistants. It is incompatible with Yuanzhi, and antagonistic to Daji, Yuanhua, Gansui, and Haizao.