精、髓、血、乳、汗、液（外出为汗，内蕴为液）、津（出于口者）、涕（蓄于脑，出于鼻）、泪、溺，皆
水也，并属于肾。而血色独红者，血为心火之化，数者色皆白，乃肺气之化也。
肾为阴，肺为阳，阳交乎阴而液以化。肾属水，心属火，水交于火而血以成，以其
为心火所成。故《经》谓心生血，又云血属于心，又云心主身之血脉也。赤者，心
火之色。心火不足，则血色淡。心气虚寒，则血凝而紫黑，紫黑为肾色自见，无火
也。亦有火盛血瘀而色紫黑者，总可见血之关于心。（张介石曰∶凡身有血处，触之必痛，痛属
心知，而赤为火色，故曰心生血。又曰∶人身麻木处，则无血色，血所不至，是心所不治，故不知痛痒。又曰∶赵
氏云血随相火行，故色红，非也。相火居坎水中，弗能自露，阳为阴掩，其色黑。至于心火，而阳老矣，阴为阳闭，
故内暗外明，其色赤。血如随相火行，则必黑而不红。）汗、液、津、泪、溺皆清澈，阳所生也。精、
髓、血、乳、涕皆稠浊，阴所成也。阳性速，其生易，故气至而即生。（如悲哀气
动，则泪若涌泉，内热蒸腾，则汗出如雨，可见。）阴性迟，其成难，故蓄积而后富。细分之，则
精、髓、涕为一类，血与乳为一类。而乳之成，较血为易，故曰血者难成而易亏。
髓藏而不泄，涕即脑髓，其泄也，以病脑热。惟精藏而能泄，其泄也，以阴阳之和
畅，故能成生育之功。血亦藏而不泄，较精之藏而能泄殊矣。故精动而血静，精阳
而血阴，（妇人之月事，乃溢而倾，非施泄之谓也。）精少血多，贵贱之别也。精生血死，老少之分
也。（精色白，肺气所化，清阳也。清阳为少火，火少则生。血色赤，心火所成，浊阳也。浊阳为壮火，火壮则
老。）水凝为冰，见 则消，血凝成块，虽煮不化，水随气行，能越于外，血随气
行，但运于中，清浊阴阳，气质之分，可观矣。旧谓血总统于心，此即心生血之义
矣。而曰化生于脾，脏受于肝，宣布于肺，施泄于肾，何也？曰∶《经》言水谷入胃，
中焦受气取汁，变化而赤为血。盖言胃中水谷之清气，藉脾运化成血，故曰化生于
脾。然儿在胎中，未尝饮食，先已有血，可见血为先天之水，不过藉后天为长养，
非全靠后天也。（又云脾统血者，则血随脾气流行之义也。）又《经》言人卧则血归于肝。盖言人
寤属阳，寐属阴，阳主外而亲上，阴主内而亲下。寤则血随阳动，外运而亲上，
卧则血随阴静，五内而亲下。五脏皆在内，而肝肾居下，为血之所归脏，言肝
而肾可该。何则？肝动肾静，动者尚脏，则静者可知，故曰脏受于肝也。（一说，血不
藏，皆肝之疏泄使然，故以脏受责之亦通。）其谓宣布于肺，则血随气行之义耳。其谓施泄于肾，则
混精为血，观古人动称父精母血可见，要知是精非血，不当混合为一也。经脉
之血流行，脏腑之血守位。以上明血之理，其病证脉治详下。
血随气行，气寒而行迟，则血涩滞。气热而行驶，则血沸腾。（盖血属阴，非阳不运，
故遇寒而凝。气属火，非少则壮，故遇热而灼。）涩滞皮肤则为痛痹，凝结经络则为疽癖，瘀积肠
胃则为败腐，虚寒不摄则为脱崩，沸腾上焦则为吐衄，流注下焦则为便血，壅塞经
脉则为痈毒，浮见皮肤则为 疹。而且湿盛而蒸为疠风，血干而化为痨蛊。致
病非一，要不出寒热二端。大抵瘀尚易治，干则难医，无潮热者轻，有潮热者重。
精、髓、血、乳、汗、液（外出为汗，内蕴为液）、津（出于口者）、涕（蓄于脑，出于鼻）、泪、溺，皆属于水，并归属于肾。而唯独血色红赤，是因为血由心火所化生，上述其他体液的颜色皆为白色，乃肺气所化生。
肾属阴，肺属阳，阳气与阴气相交则体液得以化生。肾属水，心属火，水与火相交则血液得以形成，因为血是由心火所生成的。所以《黄帝内经》说“心生血”，又说“血属于心”，还说“心主身之血脉”。红色是心火的颜色。如果心火不足，血色就会淡白；如果心气虚寒，血液就会凝滞而呈紫黑色，紫黑色是肾色的显露，说明体内无火。也有因火盛导致血瘀而呈现紫黑色的情况，总之可以看出血与心的关系密切。（张介石说：凡是身上有血的地方，触碰必然疼痛，疼痛的感觉由心主宰，而红色是火的色彩，所以说心生血。又说：人身麻木的地方，就没有血色，血不能到达那里，是心气不能治理到那里，所以不知道痛痒。又说：赵氏说血随着相火运行，所以颜色发红，这是不对的。相火居于坎水中，不能自行显露，阳气被阴气掩盖，其色黑。至于心火，阳气已经成熟，阴气被阳气闭藏，所以内部昏暗外部明亮，其色赤。如果血随着相火运行，那么必然是黑色而不是红色。）
汗、液、津、泪、溺都是清澈的，这是阳气所生的。精、髓、血、乳、涕都是稠浊的，这是阴气所成的。阳气性质迅速，生成容易，所以气一到就立即生成。（例如悲哀时气动，眼泪就像涌泉一样流出，体内热气蒸腾，汗水如雨般流出，由此可见。）阴气性质迟缓，生成困难，所以必须蓄积之后才能丰富。细分起来，精、髓、涕属于一类，血与乳属于一类。而乳的形成，比血更容易，所以说血是难成而易亏的。
髓藏而不泄，涕即是脑髓，它的排泄是因为脑部有热病。只有精能够藏而又能泄，它的排泄是因为阴阳和谐通畅，所以能完成生育的功能。血也是藏而不泄的，这与精的藏而又能泄截然不同。所以精主动而血主静，精属阳而血属阴。（妇女的月经，是满溢而出，不是施泄的意思。）精少血多，是贵贱的区别。精生血死，是老少的分别。（精的颜色白，是肺气所化，属于清阳。清阳属于少火，火少则生机旺盛。血的色赤，是心火所成，属于浊阳。浊阳属于壮火，火壮则衰老。）水凝结成冰，见到太阳就融化，血凝结成块，即使煮沸也不化开，水随着气运行，能溢出体外，血随着气运行，只在体内运输，清浊阴阳，气质的区别，由此可以观察到了。旧时说血统管于心，这就是“心生血”的含义了。而有人说血化生于脾，脏受于肝，宣布于肺，施泄于肾，为什么呢？回答说：《黄帝内经》说水谷进入胃中，中焦接受水谷之气提取汁液，变化而成为红色的血。大概意思是胃中的水谷清气，借助脾的运化功能生成血，所以说化生于脾。然而胎儿在母胎中，未曾饮食，先前就已经有了血，可见血是先天之水，不过是借助后天来长养，并非全靠后天。（又有人说脾统血，这是指血随着脾气流行的意思。）又《黄帝内经》说人卧睡时血归于肝。大概意思是人清醒属阳，睡眠属阴，阳主外而向上，阴主内而向下。清醒时血随阳气活动，向外运行而上行，卧睡时血随阴气静止，向内运行而下行。五脏都在体内，而肝肾位居下焦，是血所归藏的脏腑，说肝而肾也可以概括其中。为什么呢？肝动肾静，动的尚且属于脏，那么静的就可以推知，所以说脏受于肝。（另一种说法，血不藏，都是肝的疏泄作用使然，所以把归藏的责任归于肝也讲得通。）所谓宣布于肺，就是血随气运行的意思罢了。所谓施泄于肾，就是把精混同为血来看待，看古人动不动就说父精母血就可以明白，要知道那是精而不是血，不应当混合为一。经脉中的血流行，脏腑中的血守位。以上阐明血的道理，相关的病证脉治详见下文。
血随着气运行，气寒则运行迟缓，血液就会涩滞。气热则运行加速，血液就会沸腾。（大概血属阴，没有阳气就不能运化，所以遇到寒冷就凝结。气属火，不是少火就是壮火，所以遇到热就灼烧。）涩滞于皮肤则为痛痹，凝结于经络则为疽癖，瘀积于肠胃则为败腐，虚寒不能固摄则为脱崩，沸腾于上焦则为吐衄，流注于下焦则为便血，壅塞于经脉则为痈毒，浮见于皮肤则为疹。而且湿气盛而蒸腾则为疠风，血干枯而化为痨蛊。致病原因不一，但总不出寒热两个方面。大致来说，瘀血还容易治疗，血干则难以医治，没有潮热的病情轻，有潮热的病情重。
Essence (Jing), marrow, blood, milk, sweat, fluid (when exiting the body it is called sweat, when retained inside it is called fluid), Jin (fluids from the mouth), nasal mucus (accumulated in the brain, exiting from the nose), tears, and urine are all forms of water, and they all belong to the Kidney. The reason why blood alone is red is that blood is transformed by the Heart Fire; the colors of the aforementioned fluids are all white, which are transformations of Lung Qi.
The Kidney belongs to Yin, and the Lung belongs to Yang; when Yang interacts with Yin, fluids are transformed. The Kidney belongs to Water, and the Heart belongs to Fire; when Water interacts with Fire, blood is formed, because blood is created by the Heart Fire. Therefore, the *Classic* states that "the Heart generates blood," also says "blood belongs to the Heart," and further states that "the Heart governs the blood vessels of the body." Red is the color of Heart Fire. If Heart Fire is insufficient, the blood color will be pale. If Heart Qi is deficient and cold, blood will coagulate and turn purple-black; purple-black is the manifestation of the Kidney's color, indicating a lack of fire. There are also cases where excessive fire causes blood stasis resulting in a purple-black color; in general, this demonstrates the close relationship between blood and the Heart. (Zhang Jieshi said: Wherever there is blood in the body, touching it causes pain; pain perception belongs to the Heart's domain, and red is the color of fire, hence it is said that the Heart generates blood. He also said: In areas of numbness in the body, there is no blood color, meaning blood does not reach there, and thus the Heart cannot govern it, so one feels no pain or itch. He also stated: Zhao claimed that blood follows Xiang Huo (Ministerial Fire) in its circulation, hence its red color, which is incorrect. Xiang Huo resides in Kan Water and cannot reveal itself; Yang is obscured by Yin, so its color is black. As for Heart Fire, Yang is mature, and Yin is closed by Yang, so the interior is dark and the exterior is bright, making its color red. If blood followed Xiang Huo, it would necessarily be black, not red.)
Sweat, fluid, Jin, tears, and urine are all clear and pure, generated by Yang. Essence, marrow, blood, milk, and nasal mucus are all thick and turbid, formed by Yin. Yang nature is rapid, and its generation is easy, so when Qi arrives, it generates immediately. (For example, when sorrow moves Qi, tears flow like a spring; when internal heat steams, sweat pours like rain, as can be seen.) Yin nature is slow, and its formation is difficult, so it must accumulate before becoming abundant. Subdividing them, essence, marrow, and nasal mucus form one category, while blood and milk form another. The formation of milk is easier than that of blood, hence it is said that blood is difficult to form but easy to deplete.
Marrow is stored and not excreted; nasal mucus is essentially brain marrow, and its excretion occurs due to brain heat disease. Only essence is stored yet can be excreted; its excretion occurs due to the harmonious and smooth interaction of Yin and Yang, thereby enabling reproductive functions. Blood is also stored and not excreted, which is significantly different from essence being stored yet excretable. Thus, essence is dynamic while blood is static; essence is Yang while blood is Yin. (Menstruation in women is an overflow, not an excretion.) Essence is scarce and blood is abundant, marking a distinction of nobility and baseness. Essence represents life/youth while blood represents death/old age, marking a distinction of youth and old age. (Essence is white, transformed by Lung Qi, belonging to Clear Yang. Clear Yang is Shao Huo (Lesser Fire); less fire means vitality. Blood is red, formed by Heart Fire, belonging to Turbid Yang. Turbid Yang is Zhuang Huo (Blazing Fire); blazing fire means aging.) Water congeals into ice, which melts upon seeing the sun; blood congeals into clots, which do not dissolve even after boiling. Water moves with Qi and can exit the body externally; blood moves with Qi but circulates only internally. The distinctions of clear/turbid and Yin/Yang in their qualities can be observed here. The old view that blood is governed by the Heart aligns with the meaning of "the Heart generates blood." But why is it said that blood is transformed by the Spleen, received/stored by the Liver, distributed by the Lungs, and excreted by the Kidneys? The answer is: The *Classic* states that when food and drink enter the Stomach, the Middle Jiao receives the Qi, extracts the juices, transforms them, and turns them red to become blood. This implies that the clear Qi of food and drink in the Stomach relies on the Spleen's transportation and transformation to generate blood, hence it is said to be transformed by the Spleen. However, a fetus in the womb has not yet ingested food or drink, yet already possesses blood; this shows that blood is primordial water, merely relying on postnatal nourishment for growth, not entirely dependent on the postnatal. (Another saying regarding the Spleen controlling blood refers to the idea that blood circulates following Spleen Qi.) Furthermore, the *Classic* states that when a person lies down, blood returns to the Liver. This likely means that wakefulness belongs to Yang, sleep belongs to Yin; Yang governs the exterior and tends upward, while Yin governs the interior and tends downward. During wakefulness, blood moves with Yang, circulating outward and upward; during sleep, blood settles with Yin, moving inward and downward. All five Zang organs are internal, but the Liver and Kidney reside in the lower jiao and are the organs where blood returns. Mentioning the Liver implies the Kidney as well. Why? The Liver is dynamic, the Kidney is static; since the dynamic aspect pertains to the Zang, the static aspect can be inferred, hence it is said that the Zang receives [blood] from the Liver. (Another interpretation: Blood is not stored [by itself], but is regulated by the Liver's free flow, so attributing storage responsibility to the Liver is also valid.) The statement about distribution by the Lungs refers to the principle that blood follows Qi in its movement. The statement about excretion by the Kidneys conflates essence and blood; observing how ancients often referred to "father's essence and mother's blood" makes this clear. One must understand that this is essence, not blood, and should not be mixed together. Blood in the meridians circulates, while blood in the Zang-Fu organs remains in its proper place. The above clarifies the principles of blood; detailed pathological manifestations, pulse diagnoses, and treatments are described below.
Blood follows Qi in its movement. If Qi is cold, movement is sluggish, causing blood to stagnate. If Qi is hot, movement accelerates, causing blood to boil. (Generally, blood belongs to Yin and requires Yang to move, so it coagulates when encountering cold. Qi belongs to Fire, manifesting as either Shao Huo or Zhuang Huo, so it burns when encountering heat.) Sluggishness in the skin results in painful Bi syndrome; coagulation in the collaterals results in abscesses and masses; stasis accumulation in the intestines and stomach leads to decay and corruption; deficiency-cold failing to contain leads to prolapse and hemorrhage; boiling in the upper jiao leads to vomiting and epistaxis; flowing into the lower jiao leads to hematochezia; obstruction in the meridians leads to carbuncles and toxins; floating on the skin leads to rashes. Moreover, excessive dampness steaming leads to leprosy-like conditions; dry blood transforming leads to consumption and parasites. The causes of disease are numerous, but fundamentally fall into two categories: cold and heat. Generally, blood stasis is relatively easy to treat, whereas blood dryness is difficult to cure. Cases without tidal fever are mild, while those with tidal fever are severe.