天地之阴阳。数之可十。推之可百。数之可千。推之可万。莫窥其始，孰既其终。其切于人
身者。则内经言人之阴阳。则外为阳。内为阴。言人身之阴阳。则背为阳。腹为阴。言人身之脏腑中
阴阳。则脏者为阴。腑者为阳。肝心脾肺肾五脏皆为阴。胆胃大肠小肠膀胱三焦六腑皆为阳。
此言人身上分阴分阳之定位。然有阴中之阳有阴中之阴。有阳中之阳有阳中之阴。若背为阳。
阳中之阳。心也。阳中之阴。肺也。腹为阴。阴中之阴。肾也。阴中之阳。肝也。阴中之至阴。脾
也。按五脏皆为阴。而其表里内外雌雄相输应者。仍不离阴阳互根之义。由是则六腑概可推
矣。要之阴在内。阳之守也。阳在外。阴之使也。阴胜则阳病。故阳病治阴。阳胜则阴病。
故阴病治阳。阳胜则热。阴胜则寒者。病体之常也。重寒则热。重热则寒者。病情之变也。
此轩岐之宗旨。而仲景当日平脉辨证。分别三阴三阳之治。其大旨不越乎此然泛言阴阳。无
从把握其下手工夫。先要在表里脏腑上。分别清楚。仲景辨脉法有四语。足以蔽之。曰浮为
在表。沉为在里。数为在腑。迟为在脏。此大纲也。从此悟入。思过半矣。
内经金匮真言论。以肝心脾肺肾五脏为阴。胆胃大肠小肠膀胱三焦六腑为阳。至灵兰秘
典论。以五脏六腑合膻中为十二官。脏者为阴。足太阴脾。手太阴肺。足少阴肾。手少阴心。足
厥阴肝。手厥阴膻中。总之阴也者。藏精而起亟者也。腑者为阳。足太阳膀胱。手太阳小肠
足阳明胃。手阳明大肠。足少阳胆。手少阳三焦。总之阳也者。卫外而为固者也。然阴阳必
相维附。故脏与腑相为表里。脾与胃为表里。同从土化也。肺与大肠为表里。同从金化也。肾
与膀胱为表里。同从水化也。肝与胆为表里。同从木化也。
心与小肠相表里。同从火化也。膻中与三焦为表里。乃手少阴之别脉。摄行君火者也。此三
阴三阳之定位。至其离合之数。则更合前后上下内外互为环抱。三阳之离合。太阳为开。
阳明为阖
。少阳为枢。三阴之离合。太阴为开。厥阴为阖。少阴为枢。内经阴阳离合论。可覆按也。
不观阴阳之所以分。无以识病体之常。不观阴阳之所以合。无以达病情之变。故善诊者察色
按脉。分别阴阳。阳病治阴。阴病治阳。定其血气。各守其乡。其旨远矣。
天地间的阴阳变化，数量可以推至十，再推至百；可以推至千，再推至万。没有人能看清它的起始，也没有人能知晓它的终结。但就其与人身密切相关的部分而言，《内经》指出：论人的阴阳，外部属阳，内部属阴；论人身的阴阳，背部属阳，腹部属阴；论人身脏腑中的阴阳，脏属阴，腑属阳。肝、心、脾、肺、肾五脏皆属阴；胆、胃、大肠、小肠、膀胱、三焦六腑皆属阳。这是讲述人体上下分属阴分和阳分的固定定位。然而，其中还有阴中之阳、阴中之阴，阳中之阳、阳中之阴的区别。例如，背部属阳，阳中之阳是心；阳中之阴是肺。腹部属阴，阴中之阴是肾；阴中之阳是肝；阴中之至阴是脾。按五脏虽都属阴，但它们之间表里内外、雌雄相互对应，仍不离阴阳互根的道理。由此则可以类推六腑的情况。总之，阴在内，是阳的守持者；阳在外，是阴的役使者。阴偏胜则导致阳的病，所以治阳病要治阴；阳偏胜则导致阴的病，所以治阴病要治阳。阳偏胜表现为热，阴偏胜表现为寒，这是病体的常态。重寒转化为热，重热转化为寒，这是病情的变化。这是轩辕（黄帝）和岐伯的宗旨，而张仲景当时通过平脉辨证，区分三阴三阳的治疗原则，其大旨也不超出这个范围。然而，泛泛谈论阴阳，无法把握下手治疗的功夫，首先要在表里、脏腑上分别清楚。张仲景《辨脉法》中有四句话，足以概括这一大纲：浮脉主在表，沉脉主在里，数脉主在腑，迟脉主在脏。这是总纲。从此悟入，思虑便已过半了。
《内经·金匮真言论》以肝、心、脾、肺、肾五脏为阴，胆、胃、大肠、小肠、膀胱、三焦六腑为阳。到了《灵兰秘典论》，将五脏六腑合膻中称为十二官。脏者为阴，包括足太阴脾、手太阴肺、足少阴肾、手少阴心、足厥阴肝、手厥阴膻中，总之阴的功能是藏精并随时响应需求。腑者为阳，包括足太阳膀胱、手太阳小肠、足阳明胃、手阳明大肠、足少阳胆、手少阳三焦，总之阳的功能是护卫体表并保持固密。然而阴阳必须相互维系依附，所以脏与腑互为表里。脾与胃互为表里，同从土化；肺与大肠互为表里，同从金化；肾与膀胱互为表里，同从水化；肝与胆互为表里，同从木化；心与小肠互为表里，同从火化；膻中与三焦互为表里，乃是手少阴心的别脉，负责执行君火的作用。这是三阴三阳的固定定位。至于它们的离合之数，则是结合前后、上下、内外互为环抱的关系。三阳的离合：太阳为开，阳明为阖，少阳为枢。三阴的离合：太阴为开，厥阴为阖，少阴为枢。《内经·阴阳离合论》可以据此复核。不观察阴阳之所以分离，就无法认识病体的常态；不观察阴阳之所以聚合，就无法通达病情的变化。所以善于诊察的人，通过观察面色和按压脉搏，来分别阴阳。阳病治阴，阴病治阳，安定其血气，使各守其位，其中的旨意深远啊。
The Yin and Yang of Heaven and Earth, their numbers can be extended to ten, then to a hundred; to a thousand, then to ten thousand. No one can see their beginning, nor who knows their end. However, regarding what is closely related to the human body, *Neijing* (Classic of Internal Medicine) states: When discussing the Yin and Yang of a person, the exterior is Yang, and the interior is Yin. When discussing the Yin and Yang of the human body, the back is Yang, and the abdomen is Yin. When discussing the Yin and Yang within the Zang-Fu organs, the Zang organs are Yin, and the Fu organs are Yang. The Liver, Heart, Spleen, Lung, and Kidney, these five Zang organs, are all Yin. The Gallbladder, Stomach, Large Intestine, Small Intestine, Bladder, and Sanjiao (Triple Burner), these six Fu organs, are all Yang. This refers to the fixed positioning of Yin and Yang divisions in the upper and lower parts of the human body. However, there is Yin within Yin, Yang within Yin, Yang within Yang, and Yin within Yang. For instance, the back is Yang; among Yang, the Heart is Yang within Yang, and the Lung is Yin within Yang. The abdomen is Yin; among Yin, the Kidney is Yin within Yin, the Liver is Yang within Yin, and the Spleen is Extreme Yin within Yin. Although the five Zang organs are all Yin, their mutual correspondence in terms of exterior-interior and male-female relationships still adheres to the principle of Yin and Yang being mutually rooted. From this, the six Fu organs can be inferred by analogy. In essence, Yin inside is the guardian of Yang; Yang outside is the servant of Yin. If Yin prevails, it causes disease in Yang, so treating Yang disease requires treating Yin. If Yang prevails, it causes disease in Yin, so treating Yin disease requires treating Yang. Yang prevailing manifests as Heat, and Yin prevailing manifests as Cold; this is the constant state of the pathological body. Extreme Cold transforming into Heat, and extreme Heat transforming into Cold, are the variable changes of the disease condition. This is the purport of Xuanyuan (Yellow Emperor) and Qibo. Zhang Zhongjing’s approach at that time, through equalizing pulse diagnosis and syndrome differentiation, to distinguish the treatments for the Three Yin and Three Yang meridians, had its main purport not exceeding this. However, speaking generally of Yin and Yang makes it impossible to grasp the practical method of treatment. One must first clearly distinguish between the Exterior-Interior and the Zang-Fu. There are four phrases in Zhang Zhongjing’s *Bian Mai Fa* (Method of Differentiating Pulses) that sufficiently cover this outline: Floating pulse indicates the Exterior, Deep pulse indicates the Interior, Rapid pulse indicates the Fu organs, and Slow pulse indicates the Zang organs. This is the general principle. Entering into understanding from here means half the thinking is done.
*Neijing · Jin Gui Zhen Yan Lun* (True Words on the Golden Cabinet) regards the Liver, Heart, Spleen, Lung, and Kidney as Yin, and the Gallbladder, Stomach, Large Intestine, Small Intestine, Bladder, and Sanjiao as Yang. In *Ling Lan Mi Dian Lun* (Secrets of the Spiritual Palace), the five Zang and six Fu organs combined with Danzhong (Pericardium) are called the Twelve Officials. The Zang organs are Yin, including Foot Taiyin Spleen, Hand Taiyin Lung, Foot Shaoyin Kidney, Hand Shaoyin Heart, Foot Jueyin Liver, and Hand Jueyin Danzhong. In short, the function of Yin is storing Essence and responding promptly. The Fu organs are Yang, including Foot Taiyang Bladder, Hand Taiyang Small Intestine, Foot Yangming Stomach, Hand Yangming Large Intestine, Foot Shaoyang Gallbladder, and Hand Shaoyang Sanjiao. In short, the function of Yang is guarding the exterior and maintaining solidity. However, Yin and Yang must support and attach to each other, so Zang and Fu organs are exterior-interior pairs. The Spleen and Stomach are exterior-interior, both transforming according to Earth. The Lung and Large Intestine are exterior-interior, both transforming according to Metal. The Kidney and Bladder are exterior-interior, both transforming according to Water. The Liver and Gallbladder are exterior-interior, both transforming according to Wood. The Heart and Small Intestine are exterior-interior, both transforming according to Fire. The Danzhong and Sanjiao are exterior-interior; the Danzhong is an extra meridian of Hand Shaoyin, responsible for executing the Ministerial Fire. This constitutes the fixed positioning of the Three Yin and Three Yang. As for their separation and combination numbers, they combine front-back, up-down, and inside-outside in a mutually embracing circle. The separation and combination of the Three Yang: Taiyang is the Opening, Yangming is the Closing, Shaoyang is the Pivot. The separation and combination of the Three Yin: Taiyin is the Opening, Jueyin is the Closing, Shaoyin is the Pivot. *Neijing · Yin Yang Li He Lun* (Discussion on the Separation and Combination of Yin and Yang) can be verified accordingly. Without observing why Yin and Yang separate, one cannot understand the constant state of the pathological body; without observing why Yin and Yang combine, one cannot comprehend the variable changes of the disease condition. Therefore, a skilled diagnostician observes complexion and palpates the pulse to distinguish Yin and Yang. Treat Yang disease by addressing Yin, treat Yin disease by addressing Yang, stabilize their Qi and Blood, and let each remain in its proper place. The purport is profound.