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*Susun* (The Yellow Emperor's Inner Canon) states: When the qi of food enters the stomach, the turbid qi returns to the Heart. Leek has a pungent flavor and a foul, turbid odor, thus it is particularly easy for it to return to the Heart. Because it returns to the Heart, *Susun* states that diseases of the Heart are suitable for being treated with leek leaves. However, this applies only when the Heart is obstructed by yin pathogens and yang qi cannot penetrate; one borrows the acrid-dispersing nature of leek to unblock yang qi. It is not capable of treating all types of Heart diseases.

When pain in the epigastrium is caused by blood stasis, drinking leek juice is extremely effective. This is because leek takes the turbid qi entering the stomach and directs it to the Heart, while simultaneously using the turbid substance retained in the stomach to treat stomach conditions. Extending this principle, using it to treat chest bi (chest obstruction/pain), hematemesis and epistaxis, and ge ye (dysphagia/chest obstruction) demonstrates its merit in descending qi and dispersing blood stasis.

*Bie Lu* (Divine Farmer's Materia Medica Supplement) records that leek seeds primarily treat nocturnal emission during dreams and white urine. Zou interpreted this using the concept from *Susun*: "Yin stores essence and responds rapidly [qi ji], while Yang guards the exterior and maintains firmness." This interpretation is highly accurate. Generally, if Yang fails to anchor Yin, Yin cannot respond rapidly to store essence; if Yin fails to anchor Yang, Yang cannot maintain firmness to guard the exterior. Nocturnal emission indicates Yang failing to anchor Yin; white urine indicates Yin failing to anchor Yang. Leek has abundant roots, and its seeds enter the Kidney channel. Its sweet-warm nature is sufficient to induce rapid response [qi ji], and its sour-warm nature is sufficient to maintain firmness [wei gu]. Combining these two strengths makes it an excellent remedy for nocturnal emission and white urine. This applies only to cases where Yin and Yang fail to anchor each other. If deficiency is severe, leek seeds alone will be ineffective, and one should perhaps add warming and astringent formulas.

As for scallion (Cong): its stem is tightly wrapped in layers, white in color, and cool in nature; its leaves are hollow inside with sharp tips, green in color, and warm in nature. In all formulas by Zhang Zhongjing (Jingyue Fangshi) that use scallion, only the white part (scallion white) is used. Within those tightly wrapped layers lies the green leaf that wishes to emerge but has not yet done so. This represents "Yang contained within Yin," analogous to True Yang residing within Shaoyin. Its vital energy rises outward, containing green leaves, which resembles Jueyin; its white color resembles the Lung. Indeed, it can be considered a herb for the Liver, Kidney, and Lung.

In the syndrome of Tongmai Sini Tang (Cinnamon Twig and Aconite Decoction for Unblocking the Pulse), when the face is red, it is due to Yin repelling Yang (Yin Ge Yang). Since Yin repels Yang, it is necessary to guide Yin back to its proper place. Ginger and Prepared Aconite can support Yang and drive away Yin, but they cannot bridge the separation between Yin and Yang. Only Scallion White can elevate Yin to act as an attractant, allowing Yang to float back. Once Yang returns, the facial redness subsides. However, in the syndrome of Baitong Tang (White Unblocking Decoction), there is no facial redness. Why is Yin still elevated? Yang above should descend, and Yin below should ascend. In Shaoyin diarrhea that persists without returning, the virtue of Earthly Path (Yin ascending) is lost. Ginger and Prepared Aconite can support Yang but cannot elevate Yin to unblock Yang. If Yang is not unblocked, Yin flows downward, causing persistent diarrhea. Therefore, Scallion White is placed at the beginning of the formula, named "Baitong" (White Unblocking). Here, "Tong" (Unblocking) does not refer to unblocking the pulse, but rather to unblocking the interaction between upper and lower.

Xuanfu Huatang (Inula Flower Decoction) treats Gan Zhuo (Liver Qi Stagnation), where the patient desires someone to tread on their chest, indicating a lack of communication between upper and lower. Xuanfu Hua (Inula Flower) dissipates nodules and descends Yang; Scallion White elevates Yin and assists it to reach the upper jiao. Xinjiang (Safflower/Sang Huang) assists Xuanfu Hua. Together, they unblock the pathways of Yin and Yang, allowing upper and lower to interact and achieve Taihe (Great Harmony). Regarding women with post-miscarriage bleeding (Lanxia), the Yin of the Liver and Kidney has already sunk downward. Unless the stagnant qi in the blood vessels is unblocked and the sinking Yin is pulled upward, recovery is impossible. Xuanfu Hua and Xinjiang unblock it, while Scallion White pulls it upward. Observing these three formulas reveals the application of Scallion White for the Liver and Kidney.

However, *Ben Jing* (Shennong Ben Cao Jing) states that Scallion induces sweating, and later generations often used it in exterior-releasing formulas. What is the rationale? The Heart and Kidney are connected via the Hand-Shaoyin and Foot-Shaoyin meridians. Sweat is the fluid of the Heart. Scallion White elevates Kidney Yin, which then enters the Ying (Nutritive) level of the Heart. Being white and pungent, it also opens the depression of the Lung Wei (Defensive) level. This is how sweat is produced.