六十四难曰∶《十变》又言∶阴井木，阳井金；阴荥火，阳荥水；阴输土，阳输木；阴经
金，阳经火；阴合水，阳合土。
人身经脉，起于井穴，五脏属阴，从春夏而至秋冬，故阴井为木。阴井木生阴荥火，阴荥火
生阴输土，阴输土生阴经金，阴经金生阴合水。六腑属阳，从秋冬而至春夏，故阳井为金，阳
井金生阳荥水，阳荥水生阳输木，阳输木生阳经火，阳经火生阳合土。此阴阳逆顺之气，五行
相生之序也。
阴阳皆不同，其意何也？
然∶是刚柔之事也。阴井乙木，阳井庚金。阳井庚，庚者，乙之刚也；
阴井乙，乙者，庚之柔也。乙为木，故言阴井木也；庚为金，故言阳井金也。余皆仿此。
刚柔者，即乙庚之配合也。阴井为木，乙，阴木也。阳井为金，庚，阳金也。乙与庚合，以阴
木合阳金，故曰庚乃乙之刚，乙乃庚之柔也。阴荥火，阳荥水，是丁与壬合也。阳输木，阴输
土，是甲与己合也。阳经火，阴经金，是丙与辛合也。阳合土，阴合水，是戊与癸合也。此阴
阳配合之道也。其十干化合之义，已详三十三难中，当参互观之。
按∶《灵枢·本输篇》论井荥输经合甚详，欲求脏腑经脉之血气生死出入者，不可不知也。
其义以营卫气血，皆生于胃腑水谷之精，营行脉中，卫行脉外，血行脉中，气行脉外。然血中
有气，气中有血，阴阳互根，不可相离。是脉内之血气，从气卫而渗灌于脉外，脉外之气血，
亦从孙络而溜注于络中，外内出入之相通也。五脏内合五行，故其俞五，六腑外合六气，故其俞
六。盖六气生于五行，而有二火也。人身十二经脉，合六脏六腑之十二大络，及督脉之长强，
任脉之尾翳，脾之大包，凡二十七脉之血气，出入于手足指之间，所出为井，所溜为荥，所注
为输，所行为经，所入为合。此二十七脉之血气，从四肢通于脏腑，而脏腑中之血气，又从经
脉缪处通于孙络，而溜于络脉，交相逆顺而行，外而皮肤，内而经脉者也。夫经脉有三百六十
五穴会，络脉有三百六十五穴会，孙络亦有三百六十五穴会，经脉宽大，孙络窄小，经脉深而
络脉浅，故黄帝有五脏之所溜处，阔散之度，浅深之状，高下所至之问也。而医言过心化赤之
血，由脉管行遍，散诸微丝管，由微丝管之尾，渐并渐粗，入回血管，血入回血管，其色变紫，
与脉管交相逆顺而行，至总回管，过心入肺，呼出炭气，吸入养气，复化为赤血者，即此义也。
西医知血之行诸脉络，而不知所以能行者，气为之也。其井荥输经合五行出入之道，西医昧而
不明，是知其所当然，而不知其所以然也。
第六十四难说：《十变》中又提到：阴经的井穴属木，阳经的井穴属金；阴经的荥穴属火，阳经的荥穴属水；阴经的输穴属土，阳经的输穴属木；阴经的经穴属金，阳经的经穴属火；阴经的合穴属水，阳经的合穴属土。
人体的经脉，起始于井穴。五脏属于阴，顺应从春夏到秋冬的变化规律，所以阴井穴属木。阴井木生阴荥火，阴荥火生阴输土，阴输土生阴经金，阴经金生阴合水。六腑属于阳，顺应从秋冬到春夏的变化规律，所以阳井穴属金，阳井金生阳荥水，阳荥水生阳输木，阳输木生阳经火，阳经火生阳合土。这就是阴阳逆顺的气机变化，以及五行相生的次序。
回答说：这是刚柔配合的道理。阴井穴对应乙木，阳井穴对应庚金。阳井穴的庚，庚是乙的刚；阴井穴的乙，乙是庚的柔。乙属木，所以说阴井穴属木；庚属金，所以说阳井穴属金。其余各穴都仿照这个规律。
所谓刚柔，就是乙和庚的配合关系。阴井穴属木，乙是阴木。阳井穴属金，庚是阳金。乙与庚相合，以阴木合阳金，所以说庚是乙的刚，乙是庚的柔。阴荥穴属火，阳荥穴属水，这是丁与壬相合。阳输穴属木，阴输穴属土，这是甲与己相合。阳经穴属火，阴经穴属金，这是丙与辛相合。阳合穴属土，阴合穴属水，这是戊与癸相合。这就是阴阳配合的道理。关于十天干化合的意义，已经在第三十三难中详细论述过，应当参考对照阅读。
按语：《灵枢·本输篇》对井、荥、输、经、合五腧穴论述得非常详尽，想要了解脏腑经脉中血气的生死出入规律的人，不能不知道这些内容。
其原理在于营气、卫气和血气，都产生于胃腑消化水谷后的精微物质。营气行于脉管之中，卫气行于脉管之外，血行于脉管之中，气行于脉管之外。然而血中有气，气中有血，阴阳互为根本，不可分离。因此，脉内的血气，随着卫气渗透灌注到脉外；脉外的气血，也通过孙络流入注于络脉之中，这是内外出入相通的表现。
五脏在内配合五行，所以其腧穴有五个；六腑在外配合六气，所以其腧穴有六个。大概六气生于五行，而其中包含两种火（君火与相火）。人身十二经脉，配合六脏六腑的十二条大络，以及督脉的长强穴、任脉的尾翳穴、脾的大包穴，共二十七条经脉的血气，在手足指趾之间出入。所出的部位叫井穴，所溜注的部位叫荥穴，所灌注的部位叫输穴，所运行的部位叫经穴，所入合的部位叫合穴。这二十七条经脉的血气，从四肢通达于脏腑；而脏腑中的血气，又从经脉交会处通达于孙络，并流入络脉，相互交错、逆顺运行，外达皮肤，内连经脉。
经脉有三百六十五个穴位交会点，络脉也有三百六十五个穴位交会点，孙络同样有三百六十五个穴位交会点。经脉宽大，孙络窄小；经脉位置深，络脉位置浅。所以黄帝曾询问五脏气血所溜注之处，及其宽阔分散的程度、深浅的状态、高下到达的位置等问题。
医生所说的经过心脏化为赤色的血液，由脉管运行遍布全身，散入各种微细血管，再由微细血管的末端逐渐汇合变粗，进入回血管。血液进入回血管后，颜色变为紫色，与脉管中的血液交错逆顺运行，到达总回血管，经过心脏进入肺部，呼出二氧化碳，吸入氧气，重新转化为赤色血液。这一过程即体现了上述中医理论的含义。
西医知道血液在脉络中运行，但不知道之所以能运行的原因，是因为有“气”在推动它。对于井、荥、输、经、合五腧穴五行出入的道理，西医模糊而不明白，这是只知道其表象（所当然），而不知道其内在机理（所以然）。
The Sixty-fourth Difficulty states: The "Shi Bian" (Ten Transformations) further mentions: Yin Jing (Well) points belong to Wood, Yang Jing (Well) points belong to Metal; Yin Ying (Spring) points belong to Fire, Yang Ying (Spring) points belong to Water; Yin Shu (Stream) points belong to Earth, Yang Shu (Stream) points belong to Wood; Yin Jing (River) points belong to Metal, Yang Jing (River) points belong to Fire; Yin He (Sea) points belong to Water, Yang He (Sea) points belong to Earth.
Human meridians originate at the Jing-Well points. The Zang organs belong to Yin and follow the progression from Spring/Summer to Autumn/Winter; therefore, Yin Jing-Well points belong to Wood. Yin Jing-Well (Wood) generates Yin Ying-Spring (Fire); Yin Ying-Spring (Fire) generates Yin Shu-Stream (Earth); Yin Shu-Stream (Earth) generates Yin Jing-River (Metal); Yin Jing-River (Metal) generates Yin He-Sea (Water). The Fu organs belong to Yang and follow the progression from Autumn/Winter to Spring/Summer; therefore, Yang Jing-Well points belong to Metal, Yang Jing-Well (Metal) generates Yang Ying-Spring (Water); Yang Ying-Spring (Water) generates Yang Shu-Stream (Wood); Yang Shu-Stream (Wood) generates Yang Jing-River (Fire); Yang Jing-River (Fire) generates Yang He-Sea (Earth). This represents the Qi dynamics of Yin-Yang reversal and sequence, as well as the order of the Five Elements generating each other.
Since Yin and Yang [attributes of the Five Shu points] are different, what is the meaning behind this?
It is answered: This concerns the matter of Gang (Firm/Hard) and Rou (Soft/Yielding). Yin Jing-Well corresponds to Yi Wood, and Yang Jing-Well corresponds to Geng Metal. In Yang Jing-Well, Geng is the Gang of Yi; in Yin Jing-Well, Yi is the Rou of Geng. Since Yi belongs to Wood, it is said that Yin Jing-Well belongs to Wood; since Geng belongs to Metal, it is said that Yang Jing-Well belongs to Metal. The rest follow this pattern.
Gang and Rou refer to the pairing of Yi and Geng. Yin Jing-Well is Wood; Yi is Yin Wood. Yang Jing-Well is Metal; Geng is Yang Metal. Yi and Geng combine; combining Yin Wood with Yang Metal, it is said that Geng is the Gang of Yi, and Yi is the Rou of Geng. Yin Ying-Spring is Fire, Yang Ying-Spring is Water; this is the combination of Ding and Ren. Yang Shu-Stream is Wood, Yin Shu-Stream is Earth; this is the combination of Jia and Ji. Yang Jing-River is Fire, Yin Jing-River is Metal; this is the combination of Bing and Xin. Yang He-Sea is Earth, Yin He-Sea is Water; this is the combination of Wu and Gui. This is the way of Yin-Yang combination. The meaning of the ten Heavenly Stems' combinations has been detailed in the Thirty-third Difficulty; one should consult it for cross-reference.
Note: The "Ben Shu" chapter of the *Ling Shu* discusses the Jing-Well, Ying-Spring, Shu-Stream, Jing-River, and He-Sea points in great detail. Those who seek to understand the life, death, entry, and exit of Blood and Qi in the Zang-Fu organs and meridians must not be ignorant of these principles.
The principle lies in the fact that Ying-Qi, Wei-Qi, Blood, and Qi all originate from the essence of water and grain digested by the Stomach. Ying-Qi circulates within the vessels, while Wei-Qi circulates outside the vessels; Blood circulates within the vessels, while Qi circulates outside the vessels. However, there is Qi within Blood, and Blood within Qi; Yin and Yang are mutually rooted and cannot be separated. Thus, the Blood and Qi within the vessels permeate and irrigate outside the vessels via the Wei-Qi, and the Qi and Blood outside the vessels flow into the Luo vessels via the Sun-Luo vessels. This demonstrates the mutual connection of internal and external entry and exit.
The five Zang organs internally correspond to the Five Elements, hence their Shu points number five. The six Fu organs externally correspond to the Six Qi, hence their Shu points number six. Generally, the Six Qi arise from the Five Elements, but include two Fires. The twelve meridians of the human body correspond to the twelve major Luo vessels of the six Zang and six Fu organs, as well as Changqiang (GV1) of the Du vessel, Weiyi (CV15) of the Ren vessel, and Dabao (SP21) of the Spleen, totaling twenty-seven vessels. The Blood and Qi of these twenty-seven vessels enter and exit between the fingers and toes. What emerges is called the Jing-Well point; what trickles is called the Ying-Spring point; what pours is called the Shu-Stream point; what flows is called the Jing-River point; what enters is called the He-Sea point. The Blood and Qi of these twenty-seven vessels travel from the limbs to the Zang-Fu organs, and the Blood and Qi within the Zang-Fu organs travel from the intersections of the meridians to the Sun-Luo vessels, then flow into the Luo vessels. They move in alternating reverse and forward directions, extending outward to the skin and inward to the meridians.
There are three hundred and sixty-five intersection points for the main meridians, three hundred and sixty-five for the Luo vessels, and three hundred and sixty-five for the Sun-Luo vessels. The main meridians are broad, while the Sun-Luo vessels are narrow; the main meridians are deep, while the Luo vessels are superficial. Therefore, the Yellow Emperor asked about the places where the Qi of the five Zang organs trickles, the degree of its breadth and dispersion, its depth and superficiality, and the extent of its reach.
Physicians speak of blood that turns red after passing through the heart, which travels through the vascular tubes, disperses into various capillaries, and gradually merges and thickens from the ends of the capillaries into venous vessels. When blood enters the venous vessels, its color changes to purple. It moves in alternating reverse and forward directions relative to arterial blood, reaches the vena cava, passes through the heart into the lungs, exhales carbon dioxide, inhales oxygen, and is reconverted into red blood. This process embodies the meaning described above.
Western medicine knows that blood circulates through the vessels but does not know the reason why it can circulate, which is due to the action of Qi. Regarding the pathways of entry and exit of the Five Elements in the Jing-Well, Ying-Spring, Shu-Stream, Jing-River, and He-Sea points, Western medicine is vague and unclear. This means they know what happens (the phenomenon) but do not know why it happens (the underlying mechanism).