主治血证及水病也。
考 证
八味丸证曰∶小腹不仁。又曰∶小便不利。
以上一方，地黄八两。
芎归胶艾汤证曰∶漏下。又曰∶下血。
以上一方，地黄六两。
三物黄芩汤证曰∶在草蓐自发露、得风、四肢苦烦热。
以上一方，地黄四两。
上历观此三方，主治血及水、而不及其他也。
互 考
芎归胶艾汤、三物黄芩汤、八味丸，皆以地黄为君药。而二方言血证，一方言小便不利。
胶艾汤方中，除地黄之外，有阿胶、当归、芎 ，均是治血药也。三物黄芩汤，去地黄，则
其余无治血药品也。由是观之，古人用地黄，并治血证水病也，核焉，且也施治之法不别血
之与水亦明矣。
辨 误
夫水之与血，其素同类也。亦唯赤则谓之血，白则谓之水耳。余尝读《内经》曰∶汗者，
血之余也。问曰∶血之余，而汗白者何也？答曰∶肺者，主皮毛也，肺色白也，故汗白也。
此本于阴阳五行，而有害于疾医之道也。疾医之道，殊乎亡也？职斯之由，可悲也哉！夫汗
之白也，血之赤也。其所以然，不可得而知也。刃之所触，其创虽浅，血必出也。暑热之酷，
衣被之浓，汗必出也。壹是皆历皮毛而出者，或为汗、或为血、故以不可知为不可知，置而
不论，唯其毒所在而致治焉，斯疾医之道也。后世之医者，以八味丸为补肾剂，何其妄也？
张仲景曰∶香港脚上入，少腹不仁者，八味丸主之；又曰∶小便不利者；又曰∶转胞病，利小
便则愈；又曰∶短气有微饮，当从小便去之。壹是皆以利小便为其功。书云∶学于古训乃有
获。呜呼！学于古训，斯有获药功矣。
品 考
地黄 本邦处处出焉。其出和州者最多，而与出汉土者无异也，充实为佳。藏器曰∶《本
经》不言生干蒸干。《别录》云∶生地黄者，乃新掘鲜者是也；李时珍曰∶熟地黄，乃后人
复蒸晒者，诸家本草，皆谓干地黄为熟地黄。而今本邦药铺，以干地黄为生地黄，非也。干
者，燥干之谓，如干姜是也。生者，新鲜之名，如生姜是也。故古人言生地黄，则必言汁，
言之顺也，岂有干而有汁者哉？仲景氏之所用，生干二品而已。其熟云者，后世之为也，不
可用矣。
考证
八味丸的适应证表现为：小腹部感觉迟钝（麻木不仁）。又说：小便排出不畅。
以上这一方剂中，地黄的用量为八两。
芎归胶艾汤的适应证表现为：经血淋漓不断（漏下）。又说：下部出血（下血）。
以上这一方剂中，地黄的用量为六两。
三物黄芩汤的适应证表现为：产妇在草席上分娩后，身体暴露受风，四肢感到烦热难耐。
以上这一方剂中，地黄的用量为四两。
综上所述，纵观这三个方剂，其主治范围均为血证和水病，而不涉及其他方面。
互考
芎归胶艾汤、三物黄芩汤、八味丸，这三方均以地黄作为君药（主药）。其中两个方剂针对血证，一个方剂针对小便不利。
在胶艾汤的组方中，除了地黄之外，还有阿胶、当归、川芎，这些都是治疗血证的药物。而在三物黄芩汤中，如果去掉地黄，剩下的药物就没有治疗血证的功效了。由此看来，古人使用地黄，是同时用于治疗血证和水病的，这是经过验证的；并且可以看出，施治的方法并不区分血与水，这一点也是明确的。
辨误
水和血，本质上属于同类物质。只不过红色的称为血，白色的称为水罢了。我曾经阅读《黄帝内经》说：“汗是血的剩余部分。”请问：既然是血的剩余部分，为什么汗是白色的呢？回答说：“肺主司皮毛，肺的颜色是白色，所以汗是白色的。”这种说法基于阴阳五行理论，但却有害于临床医学的实践之道。临床诊疗之道难道已经消亡了吗？造成这种情况的原因，真是令人悲哀啊！汗之所以是白色的，血之所以是红色的，其中的原因无法得知。刀刃触碰皮肤，伤口即使很浅，血液也一定会流出。暑天炎热，衣物被褥厚重，汗水也一定会流出。无论是汗还是血，都是从皮毛排出的，有的成为汗，有的成为血，因此对于它们颜色不同的原因，应当承认不可知，搁置不论，只针对疾病的毒邪所在之处进行治疗，这才是临床医学的正道。后世的医生，把八味丸当作补肾的药剂，这多么荒谬啊！张仲景说：“脚气病之气上冲，导致小腹部感觉迟钝的，用八味丸主治；”又说：“小便不利的；”又说：“转胞病，通利小便就会痊愈；”又说：“呼吸短促且有轻微饮邪，应当通过小便排出。”这些方剂的作用都是在于通利小便。书上说：“学习古代的训诫才能有所收获。”唉！只有学习古代的经典，才能真正掌握药物的功效。
品考
地黄：在我国各地都有出产。其中以和州出产的最多，与汉土（中国内地）出产的没有区别，以质地充实为佳。藏器说：“《神农本草经》中没有记载生地黄、干地黄或蒸熟地黄的区别。《名医别录》中说：生地黄，是指新挖掘出来的新鲜药材；李时珍说：熟地黄，是后人再次蒸晒而成的，各家本草著作，都称干地黄为熟地黄。然而如今我国的药铺，将干地黄称为生地黄，这是错误的。‘干’指的是干燥处理，比如干姜就是如此；‘生’指的是新鲜状态，比如生姜就是如此。所以古人提到生地黄时，必定会提到汁液，这样才符合逻辑，哪有干燥的药材还能有汁液的道理呢？张仲景所使用的，仅有生地和干地两种。所谓的熟地黄，是后世的做法，不能使用。”
The primary indication of Rehmanniae Radix (Dihuang, 地黄) is the treatment of blood disorders and water diseases.
Textual Research
In the syndrome pattern for Ba Wei Wan (Eight-Ingredient Pill with Rehmannia Root), it states: "insensitivity in the lower abdomen." It also states: "difficulty in urination."
In the above formula, the dosage of Rehmanniae Radix is eight liang.
In the syndrome pattern for Xiong Gui Jiao Ai Tang (Cnidium, Angelica, Donkey-Hide Gelatin, and Moutan Decoction), it states: "persistent dripping bleeding." It also states: "lower body bleeding."
In the above formula, the dosage of Rehmanniae Radix is six liang.
In the syndrome pattern for San Wu Huang Qin Tang (Three-Ingredient Scutellaria Decoction), it states: "after childbirth on a straw mat, exposure to wind, causing severe irritability and heat in the four limbs."
In the above formula, the dosage of Rehmanniae Radix is four liang.
From a comprehensive review of these three formulas, their primary indications are blood disorders and water diseases, excluding other conditions.
Cross-Reference
Xiong Gui Jiao Ai Tang, San Wu Huang Qin Tang, and Ba Wei Wan all use Rehmanniae Radix as the Jun Yao (Monarch Drug). Two of them address blood disorders, while one addresses difficulty in urination.
In the composition of Jiao Ai Tang, besides Rehmanniae Radix, there are Ecliptae Herba (Ejiao, 阿胶), Angelicae Sinensis Radix (Danggui, 当归), and Chuanxiong Rhizoma (Chuanxiong, 川芎), all of which are drugs for treating blood disorders. In San Wu Huang Qin Tang, if Rehmanniae Radix is removed, the remaining ingredients have no efficacy in treating blood disorders. From this perspective, it is evident that ancient practitioners used Rehmanniae Radix to treat both blood disorders and water diseases simultaneously; this has been verified. Furthermore, it clarifies that the therapeutic method does not strictly distinguish between blood and water.
Correction of Misconceptions
Water and blood are fundamentally of the same category. The only distinction is that red fluid is called blood, and white fluid is called water. I once read in the Huangdi Neijing (Yellow Emperor's Inner Canon): "Sweat is the surplus of blood." One might ask: If sweat is the surplus of blood, why is it white? The answer given is: "The Lung governs the skin and hair; the color of the Lung is white, therefore sweat is white." This theory is based on Yin-Yang and the Five Elements, but it harms the practice of clinical medicine. Has the way of clinical medicine perished? The cause of this situation is truly lamentable! The reason sweat is white and blood is red is unknowable. When a blade touches the skin, even if the wound is shallow, blood will definitely flow. During hot summer weather, or when wearing thick clothing and bedding, sweat will definitely flow. Both sweat and blood exit through the skin and hair; some become sweat, others become blood. Therefore, regarding the reason for their different colors, we should acknowledge the unknown, set it aside without discussion, and focus solely on treating the pathogenic factors at their location. This is the true way of clinical medicine. Later physicians who regarded Ba Wei Wan as a kidney-tonifying agent were extremely erroneous. Zhang Zhongjing stated: "For foot qi ascending, causing insensitivity in the lower abdomen, Ba Wei Wan is indicated"; he also said: "For difficulty in urination"; he also said: "For bladder dysfunction (Zhuan Bao), healing occurs upon promoting urination"; he also said: "For shortness of breath due to mild fluid retention, it should be eliminated via urination." All these applications highlight its function in promoting urination. The book says: "Learning from ancient teachings leads to acquisition." Alas! Only by learning from ancient classics can one truly master the efficacy of herbs.
Product Examination
Rehmanniae Radix: Produced everywhere in our country. The production in Hezhou is the most abundant and is indistinguishable from that produced in Han territory (mainland China); it should be solid and substantial. Zang Qi stated: "Ben Jing (Shennong Ben Cao Jing) does not mention raw, dried, or steamed forms. Bie Lu (Mingyi Bie Lu) states: Raw Dihuang refers to freshly dug material; Li Shizhen stated: Cooked Dihuang is produced by later generations through repeated steaming and drying, and various materia medica texts refer to dried Dihuang as cooked Dihuang. However, currently, pharmacies in our country refer to dried Dihuang as raw Dihuang, which is incorrect. 'Dried' refers to the process of drying, such as Gan Jiang (Dried Ginger); 'Raw' refers to freshness, such as Sheng Jiang (Fresh Ginger). Thus, when ancients mentioned Sheng Dihuang, they necessarily referred to its juice, which makes logical sense. How could a dried herb contain juice? The materials used by Zhang Zhongjing were limited to two types: Sheng Di (Raw) and Gan Di (Dried). The so-called Shu Di (Cooked) is a later invention and should not be used."