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Cortex Magnoliae Officinalis (Houpo, 厚朴) is bitter and warm; it disperses dampness-induced fullness, and its qi tends toward the exterior. Rhizoma Zingiberis Recens (Zhishi, 枳实 - *Note: Standard Pinyin for Zhishi is Zhishi, Latin is Fructus Trichosanthis*) is bitter and cold; it purges hardness and fullness, and its qi tends downward. Both herbs are Qi-regulating agents for the Stomach organ. In Yangming disease, when dryness and heat accumulate in the blood aspect of the Stomach, it is appropriate to use Radix et Rhizoma Rhei (Dahuang, 大黄), a Blood-invigorating agent with the function of washing away heat and driving out excess, as the sovereign herb. However, without Qi-regulating agents leading the way, Dahuang cannot penetrate directly into the pathogenic site; this explains why these three herbs are used together. Da Chengqi Tang (Major Order the Qi Decoction) adds Natrii Sulfas (Mangxiao, 芒硝) because Mangxiao is also a Blood-agent but slightly addresses the upper jiao, just as Houpo is a Qi-agent but slightly addresses the exterior. The remaining pathogens will not linger in small amounts, and the salty-cold nature enables rapid evacuation, achieving effects beyond merely harmonizing the Stomach as Xiao Chengqi Tang (Minor Order the Qi Decoction) does.

The main indications for Zhishi and Houpo are mostly in the Middle Jiao, making them essential herbs for Chengqi formulas. However, in Zhishi Xiebai Guizhi Tang (Trichosanthes Fruit, Macrostemon Rhizome, and Cinnamon Twig Decoction), Zhishi and Houpo are used together to treat Chest Bi (Thoracic Obstruction) and rebellious Qi rushing from the hypochondrium to the heart. How should this be explained? Although one is warm-dispersing and the other cold-purging, both possess a bitter flavor with a hint of pungency, where bitterness predominates over pungency. Because they are Qi-agents that also contain pungency, their action extends to the regions of the Heart and Lungs. Since bitterness is predominant, the herbs do not stay long in the Heart and Lung regions but can be relied upon to disperse rebellious Qi and direct it downward. Zhishi is also a key herb for treating hypochondriac pain. Boiling Zhishi and Houpo extensively helps calm rebellious fullness in the chest and hypochondrium, while briefly boiling Macrostemon Rhizome (Xiebai) and others opens Yang obstruction in the chest. Separately, each fulfills its specific role; combined, they achieve remarkable synergy. The formula is named after Zhishi rather than Houpo because hypochondriac rebellion is not primarily governed by Houpo.

Is Houpo not described as having qi tending toward the exterior? Although it is not a dedicated exterior-releasing herb, it can assist in cases involving exterior symptoms, such as in Houpo Mahuang Tang (Magnolia Bark and Ephedra Decoction) which treats cough with a floating pulse, utilizing Houpo... [Text fragment implies using Houpo to address exterior/dampness].

Then, Banxia Houpo Tang (Pinellia and Magnolia Bark Decoction) treats women feeling as if there were a roasted meat piece stuck in the throat, without chest fullness, abdominal fullness, or exterior pathogens. Why is Houpo used here? The throat is the region of the Heart and Lungs. Qianjin Fang (Prescriptions Worth a Thousand Gold) highlights "chest fullness and epigastric hardness," indicating that wet-phlegm stagnation in the Heart and Chest regions causes this condition. Pinellia Tuber (Banxia), Poria (Fuling), and Zingiberis Rhizoma (Shengjiang, 生姜) have the ability to drain fluid retention and excel at draining epigastric fullness. Assisted by Perilla Leaf (Zisuye, 紫苏叶) to circulate Qi and regulate Blood, the stagnation in the Heart and Chest can become clear and open. If one does not understand that Qianjin describes the sensation as "stuck fast," neither vomitable nor swallowable, representing a pathogen firmly entrenched, it is not easily expelled. Houpo eliminates phlegm and directs Qi downward; its power is thick and its qi is vigorous, standing alone among other combinations. While other formulas may win by efficacy, Houpo wins by sheer force. Combined to form a prescription, the effect is miraculous. This is why Houpo is listed alongside Banxia.