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Fuling (Poria), Zhuling (Polyporus, *Polyporus umbellatus*), Baizhu (Atractylodis Macrocephalae Rhizoma) [each 18 zhu], Zexie (Alismatis Rhizoma) [1 liang 6 zhu half], Guizhi (Cinnamomi Ramulus) [half liang, peeled].
The above five herbs are ground into powder. Mix with rice water and take one fangcunbi (a square-inch measure) of the powder per dose. Drink plenty of warm water after taking the medicine; recovery occurs when sweating ensues.
This formula treats Taiyang exterior syndrome that has not resolved, with pathogenic factors sinking into the Fu organ (Bladder). It is suitable for patients who present with thirst and difficulty in urination. It is also a method to resolve both exterior and interior simultaneously. Because there is an exterior syndrome, Guizhi is used to treat the exterior and transform Qi. Because there is an interior syndrome, Fuling and Zexie are used to treat the interior and promote diuresis. If water fails to flow downward, it will inevitably flood upward; therefore, Baizhu is used to stabilize the Taiyin Spleen. Earth controls Water. This formula is more suitable as a powder than as a decoction, because powders linger in the Middle Jiao, regulating water passages. Furthermore, by drinking plenty of warm water, the essence of water is distributed throughout the body, flowing up and down. As heat resolves and fluids return, urination becomes smooth and thirst ceases naturally.

Note: Thirst with desire to drink water resembles the Baihu Jia Renshen Tang (White Tiger Plus Ginseng Decoction) syndrome. Why is Baihu Tang indicated for the former and Wuling San (Five-Ingredient Powder with Poria) for the latter? Generally, Baihu Tang treats Heat in the Yangming Meridian, while Wuling San treats Heat in the Taiyang Fu organ. The pulse in Baihu Tang syndrome is洪大 (Hongda, large and surging), indicating that the exterior syndrome has resolved. The pulse in Wuling San syndrome is浮数 (Fushu, floating and rapid), indicating that the exterior syndrome has not yet resolved. This serves as the basis for differentiation.
Various commentators explain the rationale of Wuling San as guiding dampness and nourishing dryness. However, relying solely on the acrid-warm nature of Guizhi, the draining properties of Fuling and Zexie, and the spleen-drying action of Baizhu seems entirely unrelated to the principle of generating fluids and moistening dryness. So why is it suitable for thirst syndromes? In this syndrome, pathogens move from the meridian to the Fu organ, causing water accumulation in the Lower Jiao, which prevents the transport of fluids to the Upper Jiao. Therefore, treating thirst requires first treating water retention. Moreover, taking the powder and drinking warm water facilitates the distribution of essence and fluids.

Zhuling (Polyporus, *Polyporus umbellatus*, peeled), Fuling (Poria), Zexie (Alismatis Rhizoma), Huashi (Talcum, crushed), Ejiao (Colla Corii Asini) [each 1 liang].
The above five herbs are boiled in four sheng (liters) of water. First, boil the first four herbs until two sheng remain. Strain the decoction, then add Ejiao and melt it. Take ten he (units of volume) warm per dose, three times daily.

Both syndromes belong to thirst with desire to drink and difficulty in urination. The Taiyang channel transforms Qi from Cold-Water; thus, Wuling San is appropriate, utilizing the sweet-warm nature of Guizhi and Baizhu to disseminate Yang and distribute essence. The Yangming channel transforms Qi from Dry-Earth; thus, Zhuling Tang (Polyporus Decoction) is appropriate, utilizing the cooling-descending nature of Huashi and Ejiao to nourish Yin and promote diuresis. However, promoting diuresis tends to consume bodily fluids. In cases of Yangming syndrome with profuse sweating and thirst, fluids are already deficient, so one should not further severely deplete the fluids.

In Shaoyin disease, if diarrhea persists for six or seven days, accompanied by cough, vomiting, thirst, irritability, and inability to sleep, why is Zhuling Tang primarily indicated? The symptoms of cough, thirst, vomiting, irritability, and insomnia appearing after diarrhea indicate that Yin fluids are being forced downward while Yang pathogens rebel upward. Zhuling Tang is used to nourish Yin and promote diuresis. This precisely leverages the exterior-interior relationship between the Shaoyin Kidney and the Taiyang Bladder. By urgently drawing Shaoyin pathogens out through the Bladder Fu organ, diarrhea stops, heat dissipates, and fluids return.