《阴阳应象论》云∶审其阴阳，以别柔刚，阳病治阴，阴病治阳，定其血气，各守其乡
，血实宜决之，气虚宜掣引之。
夫阴病在阳者，是天外风寒之邪乘中而外入，在人之背上腑 、脏 ，是人之受天外客
邪。亦有二说∶中于阳则流于经。此病始于外寒，络归外热，故以治风寒之邪，治其各脏之
；非止风寒而已，六淫湿、暑、燥、火，皆五脏所受，乃筋骨血脉受邪，各有背上五脏
以除之。伤寒一说从仲景，中八风者，有风论；中暑者，治在背上小肠 ；中湿者，治在胃
；中燥者，治在大肠 。此皆六淫客邪有余之病，皆泻在背之腑 。若病久传变，有虚有
实，各随病之传变，补泻不定，只治在背腑 。
另有上热下寒。经曰∶阴病在阳，当从阳引阴，必须先去络脉经隧之血。若阴中火旺，
上腾于天，致六阳反不衰而上充者，先去五脏之血络，引而下行，天气降下，则下寒之病自
去矣，慎勿独泻其六阳。此病阳亢，乃阴火之邪滋之，只去阴火，只损血络经隧之邪，勿误
也。
阳病在阴者，病从阴引阳，是水谷之寒热，感则害人六腑。又曰∶饮食失节，及劳役形
质，阴火乘于坤土之中，致谷气、营气、清气、胃气、元气不得上升，滋于六腑之阳气，是
五阳之气先绝于外，外者，天也。下流伏于坤土阴火之中。皆先由喜、怒、悲、忧、恐，
为五贼所伤，而后胃气不行，劳役饮食不节继之，则元气乃伤。当从胃合三里穴中推而扬之
，以伸元气，故曰从阴引阳。若元气愈不足，治在腹上诸腑之募穴；若传在五脏，为九窍不
通，随各窍之病，治其各脏之募穴于腹。故曰，五脏不平，乃六腑元气闭塞之所生也。又曰
∶五脏不和，九窍不通，皆阳气不足，阴气有余，故曰阳不胜其阴。凡治腹之募，皆为元气
不足，从阴引阳勿误也。若错补四末之 ，错泻四末之余，错泻者，差尤甚矣。按岐伯所
说，况取穴于天上，天上者，人之背上五脏六腑之 ，岂有生者乎？兴言及此，寒心彻骨！
若六淫客邪及上热下寒，筋骨皮肉血脉之病，错取穴于胃之合，及诸腹之募者必危，亦岐伯
之言下工，岂可不慎哉。
《黄帝内经·阴阳应象大论》中说：仔细辨别疾病的阴阳属性，以区分其刚柔性质，阳分有病则治疗阴分，阴分有病则治疗阳分，确定气血的虚实状态，使其各守其位。血分实证适宜用放血等方法疏通泄泻，气分虚证适宜用升提引导的方法补益。
所谓阴病在阳，是指天外的风寒邪气乘人体之中焦而外入，侵犯人体背部的腑和脏，这是人体感受了来自体外的客邪。对此有两种说法：邪气中于阳分则流注于经络。这种病始于外寒，最终归结为外热，因此治疗风寒邪气，要针对各个脏腑进行调理；这不仅仅是风寒的问题，六淫中的湿、暑、燥、火，都是五脏所受的邪气，进而导致筋骨血脉受邪，各有背部对应的五脏（此处指背俞穴）来祛除它们。关于伤寒的说法遵循张仲景的理论，中伤八风者，有专门的风病论述；中暑者，治疗取背部小肠的穴位；中湿者，治疗取胃的穴位；中燥者，治疗取大肠的穴位。这些都是六淫客邪有余的病证，都通过泻法治疗背部的腑穴。如果病情日久发生传变，出现虚证或实证，应根据病情的传变情况，补泻方法不固定，只治疗背部的腑穴。
另外还有上热下寒的情况。经书说：阴病在阳，应当从阳引阴，必须先去络脉和经隧中的瘀血。如果阴中火旺，向上腾跃至天部，导致六阳之气反而不衰而上充，此时应先去除五脏的血络之邪，引导其下行，使天气降下，那么下寒的病自然就去除了，千万不要单独泻六阳之气。这种病是阳气亢盛，是由阴火邪气滋助所致，只需清除阴火，只需损伤血络经隧中的邪气，切勿误治。
阳病在阴，是指病从阴引阳，是水谷饮食的寒热之邪，感受后伤害六腑。又说：饮食不节制，以及劳役形体体质，导致阴火乘袭位于中土的脾胃，致使谷气、营气、清气、胃气、元气不能上升，滋润六腑的阳气，这是五阳之气先在外部衰竭，外部即指天。这些气向下流伏于坤土阴火之中。这一切都先由喜、怒、悲、忧、恐五种情绪，被“五贼”所伤，然后导致胃气运行不畅，加上劳役和饮食不节继之，元气于是受伤。应当从胃经合穴足三里处推扬其气，以伸发元气，所以说是从阴引阳。如果元气更加不足，治疗应选取腹部诸腑的募穴；如果病传变到五脏，导致九窍不通，应根据各窍的病证，治疗腹部对应各脏的募穴。所以说，五脏的不平衡，是由于六腑元气闭塞所产生的。又说：五脏不和，九窍不通，都是因为阳气不足，阴气有余，所以说是阳不胜阴。凡是治疗腹部的募穴，都是为了元气不足，从阴引阳，切勿误治。如果错误地补益四肢末端的腧穴，错误地泻除四肢末端有余的邪气，错误的泻法，差错尤其严重。按照岐伯所说的话，如果在天上（背部）取穴，天上指的是人背部五脏六腑的背俞穴，难道会有生还的道理吗？想到这些，令人寒心彻骨！如果是六淫客邪以及上热下寒、筋骨皮肉血脉的病证，错误地取穴于胃的合穴及诸腹部的募穴，必定危险，这也是岐伯所说的下工（低水平医生）的行为，怎么能不谨慎呢？
As stated in the *Yellow Emperor's Inner Canon: Treatise on the Correspondence of Yin and Yang*: Carefully examine the Yin and Yang to distinguish between softness and hardness; treat Yin for Yang diseases, and treat Yang for Yin diseases. Determine the state of Qi and Blood, ensuring each remains in its proper domain. For excess conditions of Blood, it is appropriate to drain them (e.g., via bloodletting); for deficiency conditions of Qi, it is appropriate to lift and guide them.
When a Yin disease manifests in Yang, it refers to external pathogenic factors such as wind and cold from nature penetrating the middle jiao and entering outwardly, affecting the Fu and Zang organs located on the back of the human body. This constitutes the reception of external pathogenic factors by the body. There are two interpretations: when pathogens strike the Yang aspect, they flow into the meridians. Such diseases begin with external cold and ultimately resolve into external heat. Therefore, treating wind-cold pathogens involves addressing the respective Zang organs. This is not limited to wind and cold; the Six Excesses—dampness, summerheat, dryness, and fire—are also pathogens received by the Five Zang organs, subsequently affecting the sinews, bones, blood vessels, and muscles. Each has corresponding Back-Shu points on the back to eliminate these pathogens. Regarding cold damage, following Zhang Zhongjing’s theory, those struck by the Eight Winds have specific discussions on wind diseases; those struck by summerheat are treated via the Small Intestine Back-Shu point on the back; those struck by dampness are treated via the Stomach Back-Shu point; and those struck by dryness are treated via the Large Intestine Back-Shu point. These are all diseases of excess caused by external Six Excess pathogens, treated by draining the Back-Fu points. If the disease persists and transforms, presenting as either deficiency or excess, the method of tonification or drainage varies according to the transformation of the disease, focusing solely on treating the Back-Fu points.
Another condition is upper heat and lower cold. The classics state: For Yin diseases manifesting in Yang, one should draw Yin from Yang. It is necessary first to remove stagnant blood from the collaterals and channel tunnels. If Fire within Yin flares up and ascends to the Heaven level, causing the Six Yang aspects to remain undiminished and fill upward, one must first remove the blood stasis from the Five Zang collaterals, guiding it downward. When Heavenly Qi descends, the lower cold pathology will naturally dissipate. One must be cautious not to solely drain the Six Yang aspects. This condition involves Yang hyperactivity, fueled by Yin Fire pathogens. One should only clear the Yin Fire and address the pathogens in the blood collaterals and channel tunnels, avoiding mismanagement.
Yang diseases manifesting in Yin imply drawing Yang from Yin. Water and grain (dietary) cold and heat pathogens, upon invasion, harm the Six Fu organs. Furthermore, irregular diet and physical overexertion cause Yin Fire to attack the Earth element (Spleen/Stomach). This prevents Grain Qi, Ying (Nutritive) Qi, Clear Qi, Stomach Qi, and Yuan (Source) Qi from ascending to nourish the Yang Qi of the Six Fu organs. Consequently, the Yang Qi of the Five Organs fails externally first; "external" here refers to Heaven. These Qi descend and stagnate within the Yin Fire of the Earth element. All this originates from emotional injuries—joy, anger, sorrow, worry, and fear—which harm the body like the "Five Thieves," leading to impaired Stomach Qi movement. Subsequent physical exertion and dietary irregularities then injure Yuan Qi. Treatment should involve pushing and uplifting Qi from the He-Sea point of the Stomach Meridian, Zusanli (ST36), to extend Yuan Qi; thus, it is called "drawing Yang from Yin." If Yuan Qi is severely deficient, treatment focuses on the Front-Mu points of the abdominal Fu organs. If the disease transmits to the Zang organs, causing obstruction of the Nine Orifices, treatment targets the Front-Mu points of the respective Zang organs on the abdomen. Thus, it is said that imbalance in the Five Zang arises from the blockage of Yuan Qi in the Six Fu organs. It is also stated: Disharmony in the Five Zang and obstruction of the Nine Orifices are due to insufficient Yang Qi and excess Yin Qi, hence "Yang cannot overcome Yin." All treatments of abdominal Front-Mu points aim to address Yuan Qi deficiency, drawing Yang from Yin, without error. If one erroneously tonifies the extremities or erroneously drains excess at the extremities, the latter error is particularly severe. According to Qibo’s teachings, taking points on "Heaven" (the back, where the Back-Shu points of the Five Zang and Six Fu organs are located) would certainly be fatal. Reflecting on this chills one to the bone! If Six Excess pathogens, upper heat/lower cold, or diseases of sinews, bones, skin, flesh, and blood vessels are incorrectly treated by selecting the He-Sea point of the Stomach or abdominal Front-Mu points, danger is inevitable. This aligns with Qibo’s description of inferior practitioners; how can one not be cautious?