心为牡脏主血脉，牡丹色丹属心。气味辛寒，故能通血脉除血热。辛寒兼苦，直抵下焦
，故又泻肾脏阴中之火及肝热之由肾而致者。本经除症坚瘀血留舍肠胃。盖丹皮非肠胃药，
而肠胃有症坚瘀血留舍则治之，义至精而至确也。
丹皮与大黄桃仁芒硝，皆能治下焦血分之病。而仲圣方或四物并用，或有大黄桃仁芒硝
而无丹皮，或有丹皮而无大黄桃仁芒硝，或有丹皮桃仁而无大黄芒硝，或有大黄桃仁而无丹
皮芒硝，用舍之间，讵无深意。窃尝玩索而得之矣。大黄桃仁芒硝，是治客热传入之血结，
病之骤得者。丹皮是治阴虚生热之血结，病之渐致者。大黄芒硝丹皮并涤血热，而大黄下夺
而厉，芒硝咸降而濡，丹皮去瘀生新而养阴，堪入于补剂。桃仁独不凉血，而破由气入血之
闭滞。此四物功用之同而不同也。大黄牡丹汤，痈脓在大肠，丹皮冬瓜仁，乃治此证之专药
。大黄桃仁芒硝，则因发热恶寒，必其始有外邪入里，用以下夺而加之，故四物皆不可少。
桃核承气汤，表证未解而热结膀胱，宜大黄桃仁芒硝亟攻其邪，而无庸丹皮之养阴。温经汤
，病属带下而血瘀少腹，治以化气调经为主，丹皮兼疏其瘀，而无取大黄桃仁芒硝之伤正。
桂枝茯苓丸，大意与温经汤无异，而下症以止漏，下症为重，故用丹皮又加桃仁，二物性皆
柔缓，不伤胎气；若大黄芒硝之咸苦下泄，则非所宜也。下瘀血汤产妇有瘀血着脐下，非阴
虚血热之比，无需乎丹皮芒硝，既服枳实芍药散而不愈，自非大黄不能下夺，桃仁 虫逐瘀
而不峻，于产妇最宜，虽用大黄而蜜丸酒煮，用缓其性，仍所以顾产后之虚也。知此五方用
舍之
The Heart is a Yang organ (Zang) that governs the blood vessels. Peony bark (Mudanpi), with its red color, corresponds to the Heart in Five Element theory. Its flavor is pungent and cold, thus it can unblock the blood vessels and clear heat from the blood. Being pungent, cold, and slightly bitter, its action reaches directly to the Lower Jiao (Lower Burner). Therefore, it can also drain fire from the Yin aspect of the Kidney and liver heat caused by Kidney deficiency. The *Shennong Bencao Jing* records that it eliminates hard masses (Zheng) and blood stasis lodging in the stomach and intestines. Although Peony bark is not primarily a herb for the stomach and intestines, it treats these conditions when hard masses and blood stasis are present there; its rationale is extremely subtle and accurate.
Peony bark (Mudanpi), Rhubarb (Dahuang), Peach Kernel (Taoren), and Mirabilite (Mangxiao) all treat diseases of the Blood aspect in the Lower Jiao. However, in Zhang Zhongjing’s formulas, sometimes all four are used together; sometimes Rhubarb, Peach Kernel, and Mirabilite are used without Peony bark; sometimes Peony bark is used without Rhubarb, Peach Kernel, and Mirabilite; sometimes Peony bark and Peach Kernel are used without Rhubarb and Mirabilite; and sometimes Rhubarb and Peach Kernel are used without Peony bark and Mirabilite. In their use and exclusion, must there not be profound meaning? I have pondered this and understood it. Rhubarb, Peach Kernel, and Mirabilite treat blood coagulation caused by exogenous heat invading the interior; such illnesses arise suddenly. Peony bark treats blood coagulation caused by heat generated from Yin deficiency; such illnesses develop gradually. Rhubarb, Mirabilite, and Peony bark all cleanse blood heat, but Rhubarb purges violently, Mirabilite descends with a salty flavor and moistens, while Peony bark removes stasis, generates new blood, and nourishes Yin, making it suitable for inclusion in tonifying formulas. Peach Kernel alone does not cool the blood but breaks stagnation that has moved from the Qi level into the Blood level. Thus, their functions are similar yet distinct.
In *Dahuang Mudan Tang* (Rhubarb and Peony Decoction), abscesses and pus are located in the Large Intestine; Peony bark and Winter Melon Seed are specific herbs for treating this condition. When using Rhubarb, Peach Kernel, and Mirabilite, it is because the patient presents with fever and aversion to cold, indicating initial exogenous pathogens entering the interior; thus, they are used to purge downward and eliminate evil, so all four herbs are indispensable.
In *Taohe Chengqi Tang* (Peach Pit Decoction to Direct the Qi), the exterior syndrome is unresolved while heat is bound in the Bladder. It is appropriate to urgently attack the pathogen with Rhubarb, Peach Kernel, and Mirabilite, without needing the Yin-nourishing effect of Peony bark.
In *Wenjing Tang* (Warming the Menses Decoction), the disease involves leukorrhea and blood stasis in the lower abdomen. The treatment focuses on transforming Qi and regulating the menses. Peony bark assists in dispersing stasis, but one does not employ Rhubarb, Peach Kernel, or Mirabilite to avoid damaging healthy Qi.
*Guizhi Fuling Wan* (Cinnamon Twig and Poria Pill) shares a general principle with *Wenjing Tang*, but emphasizes lower abdominal symptoms (such as uterine bleeding during pregnancy). Therefore, Peony bark is used along with Peach Kernel. Both herbs have gentle properties that do not damage fetal Qi; whereas the salty and bitter downward-draining nature of Rhubarb and Mirabilite would be inappropriate.
In *Xiayuxue Tang* (Decoction to Purge Stagnant Blood), postpartum women have stagnant blood adhering below the umbilicus, which is not comparable to Yin deficiency with blood heat, so Peony bark and Mirabilite are unnecessary. Since the patient did not recover after taking *Zhishi Shaoyao San* (Immature Bitter Orange and White Peony Powder), only Rhubarb can purge downward effectively. Peach Kernel and Leech (Shuizhongzhu) remove stasis without being too harsh, making them most suitable for postpartum patients. Although Rhubarb is used, preparing it as honey pills and decocting it in wine moderates its potency, thereby protecting the deficiency inherent in the postpartum state. Understanding the rationale behind the use and exclusion in these five formulas...