黄帝针经云。凡刺之道。毕于终始。明乎终始。五脏为记。阴阳定矣。阴者、主脏。阳
者、
主腑。阳受气于四肢。阴受气于五脏。故泻者迎之。补者随之。知迎知随。气可令和。和气
之方。必通阴阳。五脏为阴。五腑为阳。
足之三阳（胃胆、膀胱之经）。从元气上至目（从九泉之下至卯。在人身为目之二。皆从
地出至卯也）。自子至卯一十二度半。
手之三阳（三焦、大肠、小肠之经）。上走手表（自开目时。始行阳道二十五度。此一十
二度半）。自卯至午一十二度半。
手之三阴（肺、心、心包络兼之）。从手下走入腹中（自阳脏也。阳受气于四肢。自天下
降行秋令。是血领诸气。乃秋自天外也）。自午至酉一十二度半。
足之三阴（脾、肾、肝之经）。元气从腹下走至足。自酉至子一十二度半。
此诸阳脏之气。受领天上。阳入于地。藏道。行冬令。入于地中。满溢不能容。地之用
及
天之体。左迁。上走出天。阴气上天。寒凉是也。故曰。地以阳杀阴藏。此之谓也。到此之
际。阴领着阳行。便是阴血先行。阳气后行。故曰。寒胜则浮。乃阴之盛气受于腹（一十二
度半）。故曰。诸阳受气于四肢。诸阴受气于五脏。此之谓也。
以上论天元真气。一昼夜五十度周于身。一刻行八丈一尺。一百三十五息。二刻转一周
天。
二百七十息。行一十六丈二尺。乃一万三千五百息。脉行八百一十丈也。非经血经水者也。
十二经水左迁。元气右迁。上上下下。无有终始。
夫天真元气者。迁推。以五味营气。谷气又为阳气。又为少阳之气奉滋养者也。经云。
三阴上奉之者、此也。
《黄帝针经》说：大凡针刺的方法，关键在于掌握“终始”的道理。明白了终始的规律，就能以五脏为记述中心，从而确定阴阳的关系。阴气主要主管五脏，阳气主要主管六腑。阳气在四肢接受精气，阴气在五脏接受精气。所以，泻法要逆着经气运行的方向刺入，补法则顺着经气运行的方向刺入。懂得迎随补泻的原则，经气就可以调和。调和经气的方法，必须通晓阴阳之道。五脏属阴，五腑属阳。
足部的三条阳经（胃、胆、膀胱的经脉），从下焦元气上行至眼部（从九泉之下升至卯位，在人体对应双眼，都是从地下升向天空）。从子时到卯时，运行十二度半。
手部的三条阳经（三焦、大肠、小肠的经脉），向上行走于体表（从睁开眼睛开始，先行于阳道二十五度，其中这一段是十二度半）。从卯时到午时，运行十二度半。
手部的三条阴经（肺、心、心包络所属的经脉），从手部走入腹中脏腑（从阳脏出发，阳气受气于四肢，如同从天下降行使秋令，这是血统领诸气，属于秋季来自天外的现象）。从午时到酉时，运行十二度半。
足部的三条阴经（脾、肾、肝的经脉），元气从腹部向下行走至足部。从酉时到子时，运行十二度半。
这些阳脏之气，接受并统领天上的阳气。阳气进入地下，遵循藏道的规律，行使冬令，深入地中。当阳气充满溢出无法容纳时，大地的作用配合天的形体，向左迁移，向上走出地面。阴气上升于天，表现为寒凉。所以说：“地以阳杀阴藏”，说的就是这个道理。到了这个时候，阴气引领阳气运行，也就是阴血先行，阳气后行。所以说：“寒胜则浮”，这是因为阴的盛气受纳于腹中（运行十二度半）。因此说：诸阳经受气于四肢，诸阴经受气于五脏，说的就是这种情况。
以上论述的是天元真气，一昼夜在全身循环五十周。每一刻运行八丈一尺，经过一百三十五息；两刻完成一周天，经过二百七十息，运行十六丈二尺。总共一万三千五百息，脉气运行八百一十丈。这并非指经络中的血液或地上的水流。十二条河流的水流方向是向左迁移，而元气则是向右迁移，上下往复，没有终点和起点。
所谓天真元气，是通过推移运动，依靠五味生成的营气、谷气来奉养，又转化为阳气，进而成为少阳之气来提供滋养。经文说：“三阴上奉之者”，指的就是这个原理。
The *Huangdi Zhenjing* (Yellow Emperor's Classic of Acupuncture) states: In all needling methods, the essence lies in understanding "Zhongshi" (the beginning and end/cycle). Once Zhongshi is clarified, the five Zang organs serve as the reference, and Yin and Yang are determined. Yin governs the Zang organs, while Yang governs the Fu organs. Yang receives Qi from the four limbs, and Yin receives Qi from the five Zang organs. Therefore, for reducing methods, one needles against the flow; for reinforcing methods, one needles with the flow. Knowing both opposing and following allows the Qi to be harmonized. The method to harmonize Qi must involve the unification of Yin and Yang. The five Zang organs are Yin, and the five Fu organs are Yang.
The three Yang meridians of the foot (Stomach, Gallbladder, Bladder meridians) ascend from the Yuan Qi (Source Qi) to the eyes (ascending from the depths below to the Mao position; in the human body, this corresponds to the two eyes, rising from the earth to the sky). From Zi hour to Mao hour, they traverse twelve and a half degrees.
The three Yang meridians of the hand (Sanjiao, Large Intestine, Small Intestine meridians) ascend to the surface of the body (starting when the eyes open, moving along the Yang pathway for twenty-five degrees; this segment accounts for twelve and a half degrees). From Mao hour to Wu hour, they traverse twelve and a half degrees.
The three Yin meridians of the hand (Lung, Heart, Pericardium meridians) move from the hands into the abdominal cavity (originating from the Yang organs; Yang receives Qi from the four limbs, descending from heaven like the autumn command, where blood leads the various Qis, originating from outside heaven in autumn). From Wu hour to You hour, they traverse twelve and a half degrees.
The three Yin meridians of the foot (Spleen, Kidney, Liver meridians) carry Yuan Qi from the abdomen down to the feet. From You hour to Zi hour, they traverse twelve and a half degrees.
The Qi of these Yang organs accepts and leads the Qi from heaven. Yang enters the earth, following the Dao of storage, executing the winter command, entering deep within the earth. When it becomes full and overflows beyond capacity, the function of the earth combines with the form of heaven, shifting left and emerging upward out of heaven. Yin Qi ascends to heaven, manifesting as coldness. Thus it is said: "Earth kills Yin through Yang storage," which refers to this principle. At this juncture, Yin leads Yang in its movement, meaning Yin Blood moves first, and Yang Qi follows later. Hence it is said: "Excess Cold leads to floating [pulse/symptoms]," because the excess Qi of Yin is received in the abdomen (traversing twelve and a half degrees). Therefore, it is stated: All Yang meridians receive Qi from the four limbs, and all Yin meridians receive Qi from the five Zang organs. This is what is meant.
The above discusses Tianyuan True Qi, which circulates fifty times around the body in one day and night. In one ke (approx. 15 minutes), it travels eight zhang and one chi, completing 135 breath cycles. In two ke, it completes one circuit of the heavens, completing 270 breath cycles, traveling sixteen zhang and two chi. In total, 13,500 breath cycles result in the pulse traveling 810 zhang. This does not refer to the blood in the Jingmai or the waters on earth. The twelve Jing Rivers flow leftward, while the Yuan Qi moves rightward, going up and down without end or beginning.
The so-called Tianzhen Yuan Qi is pushed and shifted, nourished by Ying Qi generated from the five flavors and Gu Qi (Grain Qi), which further transforms into Yang Qi, and subsequently serves as Shaoyang Qi to provide nourishment. The classics state: "What the Three Yin meridians offer upwards is this."