大黄四两 厚朴（去皮，炙）二两 枳实（大者，炙）三枚
已上三味，以水四升，煮取一升二合，去滓，分温二服。初服汤当更衣，不尔者，尽
饮之。若更衣者，勿服之。
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趺阳脉浮而涩，浮则胃气强，涩则小便数，浮涩相搏，大便则□，其脾为约，麻
仁丸主之。
【注】
趺阳，胃经脉也。趺阳脉浮而涩，阳浮则胃气强，阴涩则小便数，阴阳相搏，则热盛
而液竭矣，故大便则□也。其名为约者，谓脾为邪所约束，不能为胃行其津液，故名
脾约也。以麻仁丸主之，养液润燥，清热通幽。其不敢恣行承气者，以脉涩故也。
【集注】
程知曰：言胃脉浮涩，不可大攻，宜用麻仁丸润法也。趺阳，胃脉也。在足跗上，动
脉应手。浮则阳热盛而胃强，涩则阴津少而小便数。脾主为胃行其津液者也，胃阳强
则脾阴弱，不能为胃行其津液，故约其食物，如一、二弹丸也，此不当下而当润之。
程应旄曰：麻仁丸润燥通幽，伤寒不可恣行大承气可知矣。所以然者，以其为太阳阳
明，非正阳阳明胃家实者比也。推之少阳阳明，其不可以正阳阳明胃家实之法治之。
更可知矣。
汪琥曰：以胃强脾弱，为脾约作解。盖以胃中之邪热盛为阳强，故脉浮；脾家之津液
少为阴弱，故脉涩。用麻仁丸者，以泻胃中之阳而扶脾之阴也。
Rhizoma Rhei (Dahuang) 4 liang, Cortex Magnoliae Officinalis (Houpo) [scraped of bark and stir-fried] 2 liang, Fructus Aurantii Immaturus (Zhishi) [large ones, stir-fried] 3 pieces.
The above three ingredients are decocted in four sheng of water to obtain one sheng and two he of liquid. The dregs are removed, and the liquid is divided into two doses to be taken warm. After the initial dose, defecation should occur; if it does not, the entire remaining amount should be consumed. If defecation has already occurred, do not take the remainder.
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The Fuyang pulse is floating and choppy. Floating indicates strong Stomach Qi, while choppy indicates frequent urination. When floating and choppy interact, the stool becomes dry and difficult to pass. This condition is called "Spleen Constriction" (Pi Yue), and it is treated with Mahuang Wan (Hemp Seed Pill).
[Annotation]
Fuyang is the pulse point of the Stomach meridian. A Fuyang pulse that is floating and choppy implies that a floating Yang pulse indicates strong Stomach Qi, and a choppy Yin pulse indicates frequent urination. The interaction between Yin and Yang leads to excessive heat and depletion of fluids, resulting in dry and difficult-to-pass stools. The term "constriction" refers to the Spleen being constrained by pathogenic factors, preventing it from transporting body fluids for the Stomach; hence, it is named Spleen Constriction. Mahuang Wan is used to nourish fluids, moisten dryness, clear heat, and unblock the bowels. The reason for avoiding the liberal use of Chengqi Decoctions (such as Dachengqi Tang) is due to the choppy nature of the pulse.
[Collected Annotations]
Cheng Zhi stated: This passage indicates that when the Stomach pulse is floating and choppy, aggressive purgation should not be used; instead, the moistening method with Mahuang Wan is appropriate. Fuyang is the Stomach pulse location, located on the dorsum of the foot where the arterial pulse can be felt. Floating indicates excess Yang-heat and strong Stomach function, while choppy indicates deficient Yin-fluids and frequent urination. The Spleen's function is to transport fluids for the Stomach. When Stomach-Yang is strong, Spleen-Yin becomes weak, unable to transport fluids, thereby constraining food intake so that it passes like small pellets. This is a case requiring moistening rather than purgation.
Cheng Yingmao stated: Mahuang Wan moistens dryness and unblocks the bowels, demonstrating that in Shaoyang diseases, one must not recklessly use Dachengqi Tang. This is because this syndrome belongs to Taiyang-Yangming, which differs from Zhengyang-Yangming characterized by fullness and heat in the Stomach and Intestines (Wei Jia Shi). By extension, Shaoyang-Yangming syndromes also cannot be treated using methods for Zhengyang-Yangming Wei Jia Shi, which makes the principle even clearer.
Wang Hu stated: The etiology of Spleen Constriction is explained by strong Stomach and weak Spleen. Specifically, excessive pathogenic heat in the Stomach constitutes strong Yang, causing a floating pulse; whereas insufficient fluids in the Spleen constitute weak Yin, causing a choppy pulse. Mahuang Wan is used to drain the Yang-heat from the Stomach and support the Yin of the Spleen.