（隰草）能滋肾
熟地黄（专入肾。兼入肝）。甘而微温。味浓气薄。专补肾脏真水。兼培黄庭后土。土
浓载物
。诸脏皆受其荫。故又曰能补五脏之真阴。熟地功力甚巨。在景岳谓其真阴亏损。有为发热
、为头痛、为焦渴、为喉痹、为嗽痰、为喘气。或脾肾寒逆为呕吐。（亦有不宜用地黄者。
）
或虚火载血于口鼻。或水泛于皮肤。或阴虚而泄利。阳浮而狂躁。或阴脱而仆地。阴虚而神
散者。非熟地之守不足以聚之。（守以制散。）阴虚而火升者。非熟地之重不足以降之。（重
以制升。）阴虚而燥动者。非熟地之静不足以镇之。（静以制动。）阴虚而刚急者。非熟地之
甘不足以缓之。（缓以制急。）阴虚而水邪上沸者。舍熟地何以自制。（水以引水。）舍熟地何
以归元。阴虚而精血俱损脂膏残薄者。舍熟地何以浓肠胃。（浓以滋薄。）且犹有最玄最妙者
。则熟地兼散剂能发汗。以汗化于血。（阴以化阳。）而无阴不作汗也。熟地兼湿剂能回阳。
以阳生于下。（引阳归阴。）而无阴不回也。然而阳性速。故人参少用亦可成功。阴性缓。熟
地非多难以奏效。而今人有畏其滞腻者。则崔氏何以用于肾气丸而治痰浮。（痰本于肾。）有
畏其滑泄者。则仲景何以用于八味丸而医肾泄。（泄因肾气不固。故谓肾泄。）有谓阳能生阴
阴不能生阳者。则阴阳之理原自互根。（无阴则阳无以化。）彼此相须。缺一不可。无阳则阴
无以生。无阴则阳无以化。《内经》曰。精化为气。得非阴亦生阳乎？景岳尚论熟地。最为
明确
。独中所论脾胃寒逆为呕。可用地黄以治。是亦千虑之一失耳。夫既脾胃虚寒。则脾与胃
已受寒累。正宜用以辛热以为扫除。如太阳既至。坚冰自解。乃复坠以霜雪。投以阴剂。不
更使寒滋甚乎？余读景岳全书。见其所论。语语透辟。字字箴规。可为法守。独于所论地黄
有宜脾肾虚寒。尚有未及。虽曰熟地性温。寒从温散。然寒至上逆为呕。则寒已甚。岂有熟
地之温而可令寒外散乎？但或阳胜阴微。阳藉阴化。偶有感冒。用此杂于温散之中。或有见
效。若真纯阴无火。厥气上逆而呕。则此又为深忌。至于制用地黄。宜用好酒砂仁末同入。
久蒸久曝。使其转苦为甘。变紫为黑。方能直入肾经耳。（汪昂云。地黄性寒。得酒与火与
日则温。性滞得砂仁则利气。且能引入丹田。六味丸用之为君。尺脉弱者加桂附。所谓益火
之原以消阴翳也。尺脉旺者加知柏。所谓壮水之主以制阳光也。）出怀庆。肥大者佳。
(Relu Di Huang) can nourish the Kidney.
Shu Di Huang (Prepared Rehmanniae Radix) specifically enters the Kidney meridian and concurrently enters the Liver meridian. It is sweet in taste and slightly warm in nature, with a rich flavor but light aromatic quality. It specifically tonifies the True Yin (True Water) of the Kidney and concurrently cultivates the Spleen and Stomach (Yellow Court and Post-Heaven Earth). When the Earth element is robust, it can carry all things, and all Zang organs benefit from its influence; thus, it is also said to tonify the True Yin of the five Zang organs.
The efficacy of Shu Di Huang is profound. According to Zhang Jingyue, when there is a deficiency of True Yin, symptoms such as fever, headache, intense thirst, throat obstruction, cough with phlegm, and wheezing may occur. Alternatively, cold rebellion in the Spleen and Kidney may lead to vomiting. (There are cases where Di Huang is not suitable.)
It may also cause false fire to force blood into the mouth and nose, or water flooding onto the skin, or diarrhea due to Yin deficiency, mania due to floating Yang, or collapse due to Yin exhaustion. For those with Yin deficiency and scattered spirit, only the stabilizing property of Shu Di Huang is sufficient to gather the spirit. (Stability controls dispersion.) For those with Yin deficiency and rising fire, only the heavy nature of Shu Di Huang is sufficient to descend it. (Heaviness controls rising.) For those with Yin deficiency and restlessness, only the quiet nature of Shu Di Huang is sufficient to calm them. (Stillness controls movement.) For those with Yin deficiency and spasmodic tension, only the sweet and緩 (soothing) nature of Shu Di Huang is sufficient to relieve urgency. (Soothing controls urgency.) For those with Yin deficiency and boiling pathogenic water, what else but Shu Di Huang can self-regulate? (Using water to guide water.) What else but Shu Di Huang can return the Yuan Qi? For those with Yin deficiency and simultaneous damage to essence and blood, with depleted body fluids, what else but Shu Di Huang can thicken the intestines and stomach? (Thickening nourishes thinness.)
Moreover, there is a most subtle aspect: when combined with diaphoretic agents, Shu Di Huang can induce sweating, because sweat is transformed from blood. (Yin transforms Yang.) Without Yin, there is no sweat. When combined with yang-restoring agents, Shu Di Huang can restore Yang, because Yang is born from below. (Guiding Yang back to Yin.) Without Yin, Yang cannot return. However, Yang-tonifying herbs act quickly, so Ginseng can be effective even in small doses; Yin-nourishing herbs act slowly, and Shu Di Huang requires large doses to be effective.
Some people today fear its cloying and greasy nature. Why then did Cui Shi use it in Shen Qi Wan (Kidney Qi Pill) to treat floating phlegm? (Phlegm originates from the Kidney.) Why did Zhang Zhongjing use it in Ba Wei Wan (Eight-Ingredient Pill) to treat Kidney diarrhea? (Diarrhea is due to insecure Kidney Qi, hence called Kidney diarrhea.) Some argue that Yang can generate Yin, but Yin cannot generate Yang. However, the principle of Yin and Yang is originally mutually rooted. (Without Yin, Yang cannot transform.) They require each other; neither can do without the other. Without Yang, Yin cannot be generated; without Yin, Yang cannot be transformed. The *Nei Jing* states: "Essence transforms into Qi." Is this not also Yin generating Yang?
Zhang Jingyue's discussion on Shu Di Huang is the most clear. However, his assertion that Di Huang can be used to treat vomiting caused by cold rebellion in the Spleen and Stomach is a lapse in judgment. If the Spleen and Stomach are deficient and cold, they have already been affected by cold pathogens. One should properly use acrid and hot herbs to dispel the cold. Just as when the sun arrives, hard ice melts naturally; if one were to throw frost and snow upon it, i.e., administer Yin-cold herbs, would it not further intensify the cold?
I have read Zhang Jingyue's complete works and found his discussions thorough and his advice prudent, worthy of emulation. However, he failed to adequately address whether Di Huang is suitable for patients with Spleen and Kidney deficiency-cold. Although he stated that Shu Di Huang is warm and cold can be dispersed by warmth, when cold rebels upward causing vomiting, the cold is severe. Can the warmth of Shu Di Huang really disperse such cold externally?
If Yang is excessive and Yin is slight, and Yang relies on Yin for transformation, occasionally using this herb mixed with warming and dispersing agents for a common cold might yield results. But if it is pure Yin excess without fire, and rebellious Qi causes vomiting, this is strictly contraindicated. Regarding the preparation of Di Huang, it is best to mix it with fine rice wine and powder of Amomi Fructus (Sha Ren), steaming and drying it for a long time until its bitter taste turns sweet and its purple color turns black, allowing it to enter the Kidney meridian directly. (Wang Ang stated: Di Huang is cold in nature; with wine, fire, and sun exposure, it becomes warm. Its stagnating nature is relieved by Sha Ren, which also guides it to the Dantian. In Liu Wei Wan (Six-Ingredient Pill with Rehmannia), it is the sovereign herb. If the Chi pulse is weak, add Gui Zhi (Cinnamon Twig) and Fu Zi (Aconite Root), known as "benefiting the source of fire to eliminate yin shadows"; if the Chi pulse is vigorous, add Zhi Mu (Anemarrhenae Rhizoma) and Huang Bai (Phellodendri Cortex), known as "strengthening the master of water to control solar flare".) It originates from Huaiqing; those that are plump and large are superior.