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Dahuang (Rhei Radix et Rhizoma) has a cold nature and bitter taste, with both scent and flavor being intense. It is non-toxic, sinking in property, and belongs to Yin within Yin. It pertains to Water and Fire, entering the Hand-Yangming Large Intestine Meridian and Foot-Yangming Stomach Meridian. When soaked in wine, it enters the Taiyang (Greater Yang) Meridian; when washed with wine, it specifically enters the Yangming (Yang Brightness) Meridian. It is a miraculous pill for unblocking obstructions and consolidating knots, and an effective prescription for expelling pathogens. When used together with Taoren (Persicae Semen), it guides out blood stasis. When used together with Zhike (Aurantii Fructus), it eliminates accumulated Qi stagnation. Added to prescriptions for phlegm-fire, it can vigorously roll down stubborn phlegm; added to digestive prescriptions, it pushes out the old and generates the new. Used raw, it clears heat from gastrointestinal obstruction and accumulation; used cooked/processed, it treats various toxic sores and ulcers that fail to heal over time. This is because most toxic sores and ulcers belong to Heart Fire. When Dahuang is used processed, it can drain Heart Fire, promote Qi circulation, reduce swelling, and eliminate upper-level heat accumulation. Its nature is sinking and not floating; its action moves and does not stay fixed. It possesses the merit of pushing out the old and generating the new, and the ability to breach gates and capture generals, hence its name "General" (Jiangjun). Zhang Zhongjing used it to treat hematemesis and epistaxis due to insufficient Heart Qi, naming the formula Xiexin Tang (Drain the Heart Decoction). This is precisely because of insufficiency in the Kidney Meridian, leading to hyperactive Yang in this meridian without assistance, causing blood to act recklessly and fly away. Thus, Dahuang is used to drain the hyperactive fire, restoring peace, so that blood returns to its vessels and settles naturally. The insufficiency of Yin Qi in the Heart has not occurred in just one day; both the Lung and Liver have been affected by Fire pathogens and disease arises. Therefore, Huangqin (Scutellariae Radix) saves the Lung, and Lianhua (Loti Flos) or Lianzi (Nelumbinis Semen) [Note: Text says 'Lian', likely referring to Lianzi or related herb, but context implies clearing Liver fire, often Huanglian/Lianzi heart] saves the Liver. The Lung is the master of Yin; the Liver is the mother of the Heart and the residence of Blood. Once the Fire in the Liver and Lung recedes, Yin Blood should naturally recover. *Bencao Yan Yi* fails to state this clearly, instead saying that pathogenic heat lodges due to insufficiency. How can this clarify Zhang Zhongjing's intent and enlighten later generations? Generally, Cold cools the intestines and stomach; Bitter drains excess heat. It can only be used when there is excess pathogen in the intestines and stomach.

Xuanmingfen (Natrii Sulfas Praeparatus) has a slightly cold nature and pungent-salty taste, is non-toxic, and sinks in property, belonging to Yin. In Chengqi Tang (Harmonizing the Stomach Decoction), it is used to remove excess pathogens in the Stomach and sweep away old filth in the intestines. In Fengtu Tongsheng San (Wind-Dispersing and Unobstructed Powder), it is used to clear thick phlegm in the chest and diaphragm and moisten dryness in the lower body. For patients with smallpox/variolae presenting with excess heat and constipation, using it in Danggui Jiedu Tang (Angelica Decoction for Resolving Toxicity) is very appropriate, taking advantage of its property of not damaging True Yin. For women with retained placenta, mixing two to five qian with child's urine and administering hotly will cause the placenta to fall immediately. Generally, Cold drains excess; Salty softens hardness; Pungent disperses stagnation. These three are the merits of Xuanmingfen. I use it to replace Mangxiao (Glauberitum); even for elderly and weak persons, it can be taken.