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(Xi Cao) Cools the blood and nourishes Yin.

Dried Rehmanniae Radix (Gan Di Huang), which is the dried form of Fresh Rehmanniae Radix (Sheng Di Huang). It specifically enters the Kidney meridian, and also enters the Heart and Spleen meridians. Its taste is bitter and sweet; its nature is Yin and cold. According to Zhang Lu from Changzhou, the purple center enters the Heart, the yellow middle enters the Spleen, and the black skin returns to the Kidney. With a rich flavor but thin Qi, it internally specializes in cooling the blood and nourishing Yin, while externally moistens the skin to restore luster. For patients who are deficient internally yet have heat, it is generally suitable for use. (If there is no heat, Cooked Rehmanniae Radix (Shu Di Huang) should be used.) Dai Yuanli stated: When Yin is weak and Yang is exuberant, with Ministerial Fire (Xiang Huo) blazing strong and invading the Yin position, causing gradual consumption, leading to symptoms of Yin deficiency with fire hyperactivity, it is appropriate to use Rehmannia to nourish Yin and retreat Yang. Combined with Ginseng Radix et Rhizoma (Renshen), Poria (Fuling), and rock sugar (Shimi), it is named Qiongyu Paste (Qiongyu Gao), treating consumptive disease with cough and hemoptysis. (Specifically tonifies Lung Yin.) Combined with Asparagus Fern Root (Tian Dong), Ophiopogon Tuber (Mai Dong), Cooked Rehmanniae Radix (Shu Di Huang), and Ginseng Radix et Rhizoma (Renshen), it is named Guben Pill (Guben Wan), treating elderly individuals with exhaustion of essence and blood. (Simultaneously secures the root of the Kidney.) Adding Goji Berry Paste (Gouqi Jiang) to Guben Pill creates Jiling Paste (Jiling Gao), treating emaciation, wheezing, cough, and fatigue. (Simultaneously secures all Zang organs). Qiongyu Paste must be made by crushing fresh herbs for juice and boiling into paste using mulberry wood fire; the dispersing action contains a restraining quality, making it no different from the dried form. Both Guben Pill and Jiling Paste use dried herbs, but changing Jiling from pill to paste yields better results than Guben. *Yijian Fang* states: Men often suffer from Yin deficiency, so Cooked Rehmanniae Radix (Shu Di Huang) is suitable; women often suffer from blood heat, so Fresh Rehmanniae Radix (Sheng Di Huang) is suitable. (Use should be adjusted according to the individual.) Yu Tun said: Fresh Rehmanniae Radix (Sheng Di Huang) cools the blood, but may hinder digestion in those with weak Stomach Qi; Cooked Rehmanniae Radix (Shu Di Huang) tonifies blood, but may cause stagnation in the epigastrium for those with abundant phlegm-fluids. (These two issues—hindering digestion and causing stagnation—are critical considerations, yet why do later practitioners rarely inquire about them during clinical practice?) Some say that stir-frying Fresh Rehmanniae Radix (Sheng Di Huang) with wine prevents hindering Stomach Qi, and processing Cooked Rehmanniae Radix (Shu Di Huang) with ginger prevents epigastric stagnation. However, one must carefully examine the depth of the patient's primal Qi and pathogenic factors before use. (Understanding Zang-Fu Qi is essential for treatment.) In cases of postpartum aversion to food and diarrhea, binding pain in the lower abdomen, consumptive disease with weak Spleen and Stomach, loose stools, excessive phlegm in the chest and abdomen, obstructed Qi mechanism, and blocked ascending and descending functions, these herbs must be avoided. (Because they damage Stomach Qi!) Rehmannia produced in Zhejiang specializes in cooling blood and moistening dryness. For patients whose primal Qi is originally deficient, but due to heat-pathogen closure causing a dry, scorched-black tongue and constipation of both stool and urine, where aggressive purgation cannot be tolerated, adding this herb to heat-clearing formulas is optimal for unblocking constipation. This is because it has the function of moistening dryness without the drawback of being cloying. I observe that although *Shennong Bencao Jing* lists Rehmannia as a superior grade drug, its actual nature is Yin and soft, akin to a hypocrite, like a villain hiding flaws inside while showing tolerance outside. (This vividly describes the tendency of Yin-tonifying drugs.) Thus, renowned physicians throughout history have relied on it as a superior agent for nourishing Yin and a divine elixir for stopping bleeding. (The drawbacks remain unchanged to this day.) Although sometimes used inappropriately, it can slightly clear exuberant Qi, providing temporary relief after ingestion. Unlike Ginseng Radix et Rhizoma (Renshen), which possesses Yangming nature and resembles a gentleman, knowing faults immediately. (If a Yang-drug is unsuitable, it is readily apparent.) Therefore, physicians hesitate to use it, and patients dare not take it. Consequently, people prefer using highly Yin-softening substances like Rehmannia and Ophiopogon Tuber, even unto death, without realizing it. (Using Yin-drugs to kill people goes unnoticed by many, hence the preference for Yin as the primary approach.) Zhang Lu’s discussion is as follows. However, unless one deeply investigates pathological conditions, understands worldly affairs, and thoroughly comprehends medicinal properties, how could such profound discussion exist? Rehmannia grown in Jiangsu and Zhejiang has weak Yang energy; Rehmannia grown in the North has pure Yin and strong potency; Rehmannia grown in Huaiqing that is plump with a chrysanthemum-heart pattern is of good quality. Wine-processing directs the action upward and outward; ginger-processing prevents epigastric stagnation. It clashes with Fritillaria Bulb (Beimu) and is wary of Prunus Seed (Wuyi). It avoids Radish (Laifu), green onion, garlic, and copper/iron vessels. It works well when combined with wine, Ophiopogon Tuber (Maidong), Moutan Cortex (Danpi), and Angelicae Sinensis Radix (Danggui).