人道大阴阳有六。以立人纪。其一为先天奠位立体之阴阳。经曰。圣人南面而立。前曰广明。后曰太冲。太冲之地。
名曰少阴。少阴之上。名曰太阳。广明之下。名曰太阴。太阴之前。名曰阳明。少阴之前。名曰厥阴。厥阴之表。名曰
少阳。夫人以神立以精存。而行之以气。是以神为大君。精为储养。而气充以辅立神。必有建极之处。广而明者。所以
立极也。前之者。神君以临照接物。故前之也。后为太冲。冲以升腾为义。升其精气以济乎上。以奉神君。故即以为后。
后之者。此气从乎水位。故后之也。由太冲之地。即为少阴。少阴水位也。为藏精之腑。既藏精以自固。复升阳以腾骧。
故其上为太阳。太阳居上，充乎巅顶。为阳之极盛。要即冲脉而上之。故同冲脉。俱从少阴也。而前广明之下。复次太
阴。其前为阳明者。阳明太阴同为中土。定为国储仓廪。以赋中邦。是以太阴次广明也。少阴之前。即为厥阴。厥之云
者。绝尽之义也。厥阴居少阴之前。当太阴之下。两阴交尽而厥。而一阳即来复于此。故其表即为少阳。此少阳生九地
之下也。先立前后者。奠水火之位也。于是终太阴以司会。后少阴以宅精。底厥阴以成终成始。此三阴之正也。太阳居
华盖之上。阳明充中土之贡。少阳起太和之气于绝苏之会。此三阳之正也。三阳皆三阴者。阴为阳宅也。
其二为形气致用之阴阳。经曰。三阳为经。二阳为维。一阳为游部。三阴为表。二阴为里一阴绝作朔晦。夫阳有气
而无质。阴有质而有部。故阳能主阴。而阴得奉阳。阳者人之生气也。生气莫盛于三阳。三阳为生人之大主。其气能贯
脏腑。而立十二经。故三阳为经。所谓经者。大经大本也。二阳充满在中。所以会肌肤。束筋体。扼四关。缴四末。故
为维。维。维系之也。游部者。初阳起下。其气轻柔。升其和德。进临诸经。而无所不达。故为游部。盖阳以气为主。
而其用则自下而上。分为三部。少阳自下。阳明在中。太阳尊盛在上。其体用如是也。三阴则有形质矣。外而官体。内
而脏腑。以及精液血肉骨脉。凡属有形质者。皆阴为之。是以得分表里焉。阴之大总为三阴。宅中而主形躯肌肉。故为
表。二阴为受精之宅。受五脏六腑之精而藏之。是以得主脏腑而主内。故为里。一阴绝者。在下之穷阴也。阴尽则阳生。
象晦而复朔。故云作晦朔也。三阴既有质有部。则其形层如是。盖三阳为纵。三阴为横。合之形气。所以致用也。
其三为上下倡和。雌雄相应之阴阳。经曰。三阳为父。三阴为母。二阳为卫。二阴为雌。一阳为纪一阴为独使。易
曰。
一阴一阳之谓道。夫阴阳必两相倡和而能鼓舞。一则神。两故化也。是以言三阳之尊。必及三阴之亲者。有其尊必不容
废其亲也。二阳二阴。言卫与雌者。卫以营其外。雌以缮其内。其居中用事譬犹处家之道。必夫妇亲之也。纪与独使者。
游缴之任。在一阳罢极之肩。在一阴相合而始。备行役传宣之用。譬之行旅。有车骑必给刍茭也。此阴阳之输应。不可
不合两也。
其四为自相鼓荡。以各成一致之阴阳。经曰。太阳为开。阳明为阖。少阳为枢太阴为开。厥阴为阖。少阴为枢。阴
阳既以合两为功。又以一致为和。合两则共为开阖。各一则自为开阖。盖阴阳之用。总以鼓铸为事。三阴三阳。虽各处
形层部位。而要其共气。则阳与阳对。阴与阴伍。必自相得以为和。故亦自为开阖。各有枢以持其间者。所以致开阖之
用也。太阳盛于卫外。故为开。阳明充于营中。故为阖。少阳能与之参和。故为枢。必三者备而合为阳之用。乃以成其
一致。而其脉乃搏而勿浮也。太阴健运。而其气不藏。故主开。厥阴潜藏。而其气不扬。故主阖。少阴蓄水藏火。独兼
二气。故主枢。有枢而两阴始不迫促。是以能合而致一阴之用。而其脉乃搏而勿沉也。其五为脏腑立职之阴阳。先天阴
阳既有部位。则设官分职以守之脏腑者以五。五行部署。应天之官。而分之以职者也。脏以藏神。腑以备器。其贵贱相
使。各殊其位。经曰。心为君主。为阳中之太阳。肺为相傅之官。为阳中之少阴。心主夏。肺主秋。二脏位胸中膻中。
所谓阳而在上。即应天之燥热在上者也。脾胃者。仓廪之官。为阴中之至阴。主季夏。阴中者。脾属足部。至阴者中土
坤德。以顺天承。而不以阳居也。胃为水谷之海。当两阳合明。以合乎太阴。故亦同居中土。即应天所谓土居其中也。
肾为蛰藏之官。为阴中之太阴。肝为将军之官。为阴中之少阳。一主冬。一主春。肾既藏精。为先天寒水。与心太阳为
对。故即名太阴。肝从一阳来复。而起风木主令。故为少阳。二脏居足阴部。而又在下。即应天之风寒在下也。胆为中
正之官。十一脏皆取决焉。以一阳之生气。为太和之元神。而游部三焦。出入经络。即应天所为大游行其间者也。外此
则膀胱为州都。大小肠为传送。以备器致用。经云。此皆至阴之类。通乎土气。而不得以应天矣。前广明章。阴阳奠其
地分。而此脏腑分其守职。故谓五脏能立阴阳则可。谓地分阴阳即五脏则非也。凡内经论阴阳病。不拈脏腑。职是故耳。
其六为营气隧道。并行出入之阴阳。此为经络也。经络者。以其经连属五络。以通部分。为隧道以出阴入阳。出阳入阴。
总为通衢。而每经隧道。又各交属互络。通乎上下。所以各经有表里之名。此表里要非太阴阳所主之表里也。足三阴从
足入腹。手三阴从腹出手。六阴皆以次相接于腹中。手三阳从手走头。足三阳从头走足。六阳皆以次相接于头上。腹中
者。以阴接阴。头上者。以阳接阳。其至于手。则以内阴接外阳。其至于足。则以外阳接内阴。所谓隧道也。而各经并
行者。在手则太阴肺。出臂内上廉。阳明大肠。即出臂外上廉。少阴心。出臂内下廉。太阳小肠。即出臂外下廉。厥阴
心包。出臂内中道。少阳三焦。即出臂外中道。足三阴三阳亦然。兹则以其隧道并行。所谓表里也。若不识脏腑阴阳体
用。又不知经络。此表彼里。是犹众盲摸象也。是以得条列而着之。
人道的大阴阳分为六类，以此确立人伦纲纪。
第一类是先天奠定位置、确立本体的阴阳。《内经》说：圣人面南而立，前方称为广明，后方称为太冲。太冲之地，名为少阴。少阴之上，名为太阳。广明之下，名为太阴。太阴之前，名为阳明。少阴之前，名为厥阴。厥阴之表，名为少阳。人凭借神而建立生命，凭借精而存在，并依靠气来运行。因此，神是大君，精是储备滋养之物，而气则充实以辅助确立神的存在。这必然有一个建立极点的所在。“广明”是用来建立极点的。所谓“前”，是因为神君在上面临照并接触万物，所以称为前。后方为太冲，“冲”意为升腾，升发精气以济助上方，以奉养神君，所以作为后。所谓“后”，是因为此气来源于水位（北方/肾），所以位于后。从太冲之地，即为少阴。少阴属水，是藏精的腑脏。既然藏精以自我巩固，又升发阳气以腾跃上升，所以其上部为太阳。太阳居于上部，充盈于头顶，是阳气极盛之处。它依托冲脉而上行，所以与冲脉一样，都源于少阴。而在前方广明之下，接着是太阴。太阴的前方是阳明。阳明和太阴同属中土，被定为国家的储备粮仓，以供给中央邦国。因此太阴次于广明。在少阴的前方，就是厥阴。“厥”的意思是绝尽。厥阴位于少阴之前，处在太阴之下，两阴交尽而绝，此时一阳开始来复于此。所以它的表层就是少阳。这个少阳生于九地之下。先确立前后，是为了奠定水火的位置。于是以太阴终结并主持会合，以后面的少阴安住精气，以底层的厥阴完成终结与开始。这是三阴的正统。太阳居于华盖（头顶部）之上，阳明充当中土的贡赋，少阳在绝苏（生机萌发）之处兴起太和之气。这是三阳的正统。三阳都是三阳者，因为阴是阳的宅舍。
第二类是形体与气机发挥作用的阴阳。《内经》说：三阳为经，二阳为维，一阳为游部。三阴为表，二阴为里，一阴绝作朔晦。阳有气而无实质，阴有实质而有部位。所以阳能主导阴，而阴能奉养阳。阳是人的生气。生气没有比三阳更旺盛的。三阳是生人的大主宰，其气能贯通脏腑，并确立十二经脉。所以三阳称为“经”，所谓的“经”，是指大经大本。二阳充满在中间，用来会合肌肤，束缚筋体，扼守四关，连接四肢末端。所以称为“维”，即维系的意思。“游部”是指初生的阳气起于下部，其气轻柔，升发和顺之德，进临各条经脉，无所不达。所以称为“游部”。大概阳以气为主，而其作用则是自下而上，分为三部。少阳在下，阳明在中，太阳尊盛在上。它们的体用就是这样。三阴则有了形质。外在表现为官体，内在为脏腑，以及精液、血肉、骨、脉，凡是属于有形质的，都由阴所构成。因此可以分表里。阴的大总称为三阴，宅居中部并主管形躯肌肉，所以称为表。二阴是接受精华的宅舍，接受五脏六腑的精气而储藏它。所以主管脏腑而主内，因此称为里。一阴绝，是指在下部的穷尽之阴。阴尽则阳生，象征晦暗之后又转为朔日（新月），所以称为作晦朔。三阴既然既有质又有部，那么它们的形体层次就是这样。大概三阳为纵，三阴为横，结合形体与气机，以此来发挥作用。
第三类是上下唱和、雌雄相应的阴阳。《内经》说：三阳为父，三阴为母。二阳为卫，二阴为雌。一阳为纪，一阴为独使。《易经》说：一阴一阳叫做道。阴阳必须两相唱和才能鼓舞生机，单一则显神妙，两相则化生万物。所以说三阳之尊贵，必须提及三阴之亲近，因为有尊贵就不能废弃亲近。二阳和二阴，讲卫与雌，卫用以营护外部，雌用以修缮内部。它们居中起作用，好比居家之道，必须夫妇相亲。纪与独使，是游走连接的任务，在一阳罢极（极度疲劳/极点）的肩膀上，在一阴相合的开始处，具备执行传宣任务的功用，好比旅行，有车骑就必须提供草料。这是阴阳的输应，不可不合并两者。
第四类是自相鼓荡，以各自达成一致的阴阳。《内经》说：太阳为开，阳明为阖，少阳为枢；太阴为开，厥阴为阖，少阴为枢。阴阳既然以合两为功，又以一致为和。合两则共同作为开阖，各守其一则各自作为开阖。大概阴阳的作用，总以鼓铸变化为事。三阴三阳，虽然各处不同的形体层次和部位，但追究其共有的气，则是阳与阳相对，阴与阴为伍，必须自相得以为和。所以也各自作为开阖，各有枢机持守其间，以此来发挥开阖的作用。太阳盛于卫外，所以为开。阳明充于营中，所以为阖。少阳能与它们参和，所以为枢。必须三者具备而合为阳之用，才能成就其一致性，其脉象乃搏动而不浮。太阴健运，其气不藏，所以主开。厥阴潜藏，其气不扬，所以主阖。少阴蓄水藏火，独兼二气，所以主枢。有枢机而两阴才开始不迫促，因此能合而致一阴之用，其脉象乃搏动而不沉。
第五类是为脏腑设立职司的阴阳。先天的阴阳既然有了部位，就设置官职来守护它们。脏腑共有五个，五行部署，对应天上的官职，并分配以职司。脏用来藏神，腑用来备器。它们的贵贱相互驱使，地位各不相同。《内经》说：心为君主，是阳中之太阳。肺为相傅之官，是阳中之少阴。心主夏，肺主秋。这两脏位于胸中膻中，所谓阳而在上，即对应天上燥热在上的情况。脾胃是仓廪之官，是阴中之至阴，主季夏。阴中，指脾属足部；至阴，指中土坤德，顺应天道承继，不以阳居位。胃是水谷之海，当两阳合明之时，以合乎太阴，所以也同居中土，即对应天上所谓土居其中的情况。肾是蛰藏之官，是阴中之太阴。肝是将军之官，是阴中之少阳。一个主冬，一个主春。肾既藏精，为先天寒水，与心太阳相对，所以命名为太阴。肝从一阳来复，而起风木主令，所以为少阳。这两脏位于足阴部，而又在下，即对应天上风寒在下的情况。胆是中正之官，十一脏都取决于它。以一阳的生气，作为太和的元神，而游部于三焦，出入经络，即对应天上所谓大游行于其间的情况。除此之外，膀胱为州都，大小肠为传送，以备器致用。经云：这些都属于至阴之类，通乎土气，而不能对应天象了。前面的广明章，阴阳奠定了地域分工，而这里脏腑划分了职守。所以说五脏能确立阴阳是可以的，说地域分工的阴阳就是五脏则是不对的。凡是《内经》论述阴阳病，不特意拈出脏腑，就是这个原因。
第六类是营气隧道，并行出入的阴阳。这就是经络。经络，因为它连接五络，以通达部分，作为隧道以出阴入阳、出阳入阴，总共成为通衢大道，而每条经的隧道，又各自交错隶属互络，通达上下。所以各经都有表里的名称。这种表里主要不是太阴和太阳所主的表里。足三阴从足进入腹部，手三阴从腹部出手。六阴都在腹部依次相接。手三阳从手走向头，足三阳从头走向足。六阳都在头部依次相接。在腹中，是以阴接阴；在头上，是以阳接阳。至于手部，则是以内阴接外阳；至于足部，则是以外阳接内阴。这就叫隧道。而各经并行的是：在手部，太阴肺经出于臂内上廉，阳明大肠经即出于臂外上廉；少阴心经出于臂内下廉，太阳小肠经即出于臂外下廉；厥阴心包经出于臂内中道，少阳三焦经即出于臂外中道。足部的三阴三阳也是如此。这里说的是以其隧道并行，这叫表里。如果不认识脏腑阴阳的体用，又不知道经络，这就如同众盲摸象，分不清此表彼里。因此得以条理列述并记载下来。
The Great Yin-Yang of Human Affairs is divided into six categories, thereby establishing the ethical bonds of humanity.
The first category is the Yin-Yang that establishes position and substance in the prenatal state. The Classic states: "When the sage stands facing south, the front is called Guangming (Broad Brightness), and the back is called Taichong (Great Surge). In the place of Taichong, it is named Shaoyin (Lesser Yin). Above Shaoyin, it is named Taiyang (Greater Yang). Below Guangming, it is named Taiyin (Greater Yin). Before Taiyin, it is named Yangming (Bright Yang). Before Shaoyin, it is named Jueyin (Terminal Yin). On the exterior of Jueyin, it is named Shaoyang (Lesser Yang)." Humans are established by Shen (Spirit) and sustained by Jing (Essence), with Qi (Vital Energy) facilitating movement. Thus, Shen is the Great Ruler, Jing is the stored nourishment, and Qi fills and assists in establishing Shen. There must be a place where the Ultimate is established. Guangming serves to establish this Ultimate. The term "front" implies that the Spirit Ruler looks down from above and interacts with things, hence it is called front. The back is Taichong; "Chong" signifies ascending and rising. It ascends Jing-Qi to assist the upper region to serve the Spirit Ruler, hence it is placed at the back. The term "back" indicates that this Qi originates from the Water position (North/Kidney), hence it is behind. From the place of Taichong arises Shaoyin. Shaoyin belongs to Water and is the fu-organ storing Jing. Having stored Jing to consolidate itself, it also raises Yang-Qi to soar upwards; thus its upper part is Taiyang. Taiyang resides in the upper region, filling the vertex, representing the peak of Yang. It ascends relying on the Chong Mai (Penetrating Vessel), so like the Chong Mai, it originates from Shaoyin. Below Guangming in the front follows Taiyin. Before Taiyin is Yangming. Yangming and Taiyin both belong to Central Earth, designated as the state's granary to supply the central regions. Therefore, Taiyin follows Guangming. Before Shaoyin lies Jueyin. "Jue" means termination or exhaustion. Jueyin is located before Shaoyin and below Taiyin; when two Yins intersect and exhaust, one Yang begins to return here. Thus, its exterior is Shaoyang. This Shaoyang arises from beneath the nine earths. Establishing front and back first is to set the positions of Water and Fire. Thus, Taiyin concludes and presides over the convergence; Taichong (Shaoyin) houses the Essence; and Jueyin completes the end and beginning. This is the orthodoxy of the Three Yin. Taiyang resides above the Huagai (Canopy/Vertex); Yangming fills the tribute of Central Earth; Shaoyang rises with the Taihe (Great Harmony) Qi at the juncture of revival. This is the orthodoxy of the Three Yang. The Three Yang correspond to the Three Yin because Yin is the dwelling of Yang.
The second category is the Yin-Yang of form and function. The Classic states: "The Three Yang constitute the Jing (Meridians/Main Lines); the Two Yang constitute the Wei (Maintenance/Bridle); the One Yang constitutes the Youbu (Wandering Department). The Three Yin constitute the Biao (Exterior); the Two Yin constitute the Li (Interior); the One Yin terminates and resembles the dark and bright phases of the moon." Yang has Qi but no substantial form; Yin has substantial form but specific locations. Therefore, Yang governs Yin, and Yin supports Yang. Yang is the Shengqi (Vital Qi) of humans. Vital Qi is most vigorous in the Three Yang. The Three Yang are the great masters of life; their Qi penetrates the Zang-Fu organs and establishes the Twelve Meridians. Hence, the Three Yang are called "Jing," meaning the great roots and foundations. The Two Yang are full in the middle, used to converge skin and muscles, bind sinews and bones, guard the four gates, and connect the four extremities. Hence they are called "Wei," meaning maintenance or bridle. "Youbu" refers to the initial Yang arising from below; its Qi is light and gentle, raising harmonious virtue and advancing to all meridians, reaching everywhere. Hence it is called "Youbu." Generally, Yang is primarily Qi, and its function moves from bottom to top, divided into three parts: Shaoyang is below, Yangming is in the middle, and Taiyang is supreme above. Their substance and function are thus. The Three Yin possess substantial form. Externally they manifest as body parts, internally as Zang-Fu organs, and also as Jing fluids, blood, flesh, bone, and vessels. All that has substantial form is governed by Yin. Thus, they can be divided into Exterior and Interior. The general category of Yin is the Three Yin, which dwell in the center and govern the physical body and muscles, hence called Exterior. The Two Yin are the dwellings receiving essence, storing the essence of the Five Zang and Six Fu organs. Thus they govern the Zang-Fu and are internal, hence called Interior. The One Yin terminating refers to the exhausted Yin at the lower extreme. When Yin ends, Yang is born, resembling the transition from the dark (Hui) to the new moon (Shuo), hence termed "resembling Hui and Shuo." Since the Three Yin have substance and location, their structural layers are as described. Generally, the Three Yang are longitudinal, and the Three Yin are transverse. Combining form and Qi allows for functional application.
The third category is the Yin-Yang of mutual resonance between upper and lower, and correspondence between male and female. The Classic states: "The Three Yang are the Father; the Three Yin are the Mother. The Two Yang are the Wei (Defensive); the Two Yin are the Ci (Female/Matriarch). The One Yang is the Ji (Discipline/Regulation); the One Yin is the Dushi (Solo Messenger)." The I Ching states: "One Yin and one Yang is called the Dao." Yin and Yang must mutually resonate to stimulate vitality; unity brings spirit, duality brings transformation. Therefore, speaking of the dignity of the Three Yang necessitates mentioning the intimacy of the Three Yin; dignity cannot discard intimacy. Regarding the Two Yang and Two Yin, discussing Wei and Ci: Wei protects the exterior, while Ci repairs the interior. Occupying the center and functioning, it is like the way of a household, requiring husband and wife to be close. Ji and Dushi perform wandering and connecting duties; Ji rests on the shoulder of the One Yang (at the point of exhaustion/extremity), and Dushi begins where the One Yin combines. They prepare for travel and communication duties, like travelers needing fodder for chariots and horses. This transmission and response of Yin and Yang cannot fail to combine the two.
The fourth category is the self-stimulating Yin-Yang, achieving consistency through individual roles. The Classic states: "Taiyang is Kai (Opening); Yangming is He (Closing); Shaoyang is Shu (Pivot). Taiyin is Kai; Jueyin is He; Shaoyin is Shu." Yin and Yang achieve merit by combining two, and harmony by achieving unity. Combining two means jointly acting as Opening and Closing; each maintaining its own role means individually acting as Opening and Closing. The function of Yin and Yang generally involves forging and transforming. Although the Three Yin and Three Yang occupy different structural layers and locations, regarding their shared Qi, Yang pairs with Yang, and Yin groups with Yin, seeking harmony through mutual compatibility. Thus, they also act as Opening and Closing individually, each holding a Pivot in between to facilitate these functions. Taiyang is strong in defending the exterior, hence it is Kai. Yangming fills the Ying (Nutritive) interior, hence it is He. Shaoyang can harmonize with them, hence it is Shu. Only when all three are present and combined does the function of Yang complete its consistency, resulting in a pulse that is firm but not floating. Taiyin is robust in transport, and its Qi does not store, hence it governs Kai. Jueyin hides deeply, and its Qi does not rise, hence it governs He. Shaoyin stores water and fire, uniquely combining two Qi, hence it governs Shu. With a Pivot, the two Yins do not become constrained, allowing them to unite and achieve the function of Yin, resulting in a pulse that is firm but not sunken.
The fifth category is the Yin-Yang establishing official duties for the Zang-Fu organs. Since the prenatal Yin-Yang has established positions, officials are appointed to guard them. There are five Zang-Fu sets, corresponding to the Five Elements' deployment, mirroring heavenly offices, and assigned specific duties. Zang organs store Shen; Fu organs prepare vessels. Their hierarchy dictates distinct positions. The Classic states: "The Heart is the Monarch, being Taiyang within Yang. The Lung is the Official of Minister, being Shaoyin within Yang. The Heart governs Summer; the Lung governs Autumn. These two organs reside in the chest at Danzhong. This is 'Yang located above,' corresponding to the dry heat of Heaven located above." The Spleen and Stomach are Officials of Granaries, being Zhiyin (Supreme Yin) within Yin, governing late summer. "Yin within" indicates the Spleen belongs to the foot; "Zhizhi" refers to the virtue of Central Earth (Kun), complying with Heaven's succession, not occupying a Yang position. The Stomach is the Sea of Water and Grain, occurring when two Yangs combine (Ming), harmonizing with Taiyin, thus also residing in Central Earth, corresponding to Earth located in the center of Heaven. The Kidney is the Official of Hibernation, being Taiyin within Yin. The Liver is the General, being Shaoyang within Yin. One governs Winter, the other Spring. The Kidney stores Jing, constituting the prenatal Cold Water, opposing the Heart-Taiyang, hence named Taiyin. The Liver arises from the returning One Yang, initiating Wind-Wood governance, hence Shaoyang. These two organs reside in the foot-Yin region and are lower, corresponding to Wind and Cold located below in Heaven. The Gallbladder is the Official of Integrity, from whom all eleven organs decide. Using the Shengqi of One Yang as the primordial spirit of Great Harmony, it wanders through the Sanjiao (Triple Burner), entering and exiting meridians, corresponding to the great roaming in Heaven. Beyond these, the Bladder is the City of Accumulation, and the Large and Small Intestines are for transmission, serving vessel functions. The Classic says: "These all belong to the category of Zhiyin, connecting with Earth Qi, and cannot correspond to Heavenly phenomena." In the previous Guangming chapter, Yin-Yang established territorial divisions; here, Zang-Fu divide official duties. Thus, it is correct to say the Five Zang can establish Yin-Yang, but incorrect to say the territorial division of Yin-Yang *is* the Five Zang. Whenever the Neijing discusses Yin-Yang diseases without explicitly citing Zang-Fu, it is for this reason.
The sixth category is the Ying-Qi tunnels, parallel pathways of entry and exit. This refers to the Jing-Luo (Meridians and Collaterals). The Meridials connect the Five Networks to communicate specific regions, serving as tunnels to move Yin out to Yang and Yang out to Yin, forming major thoroughfares. Each meridian's tunnel intersects and links with others, communicating up and down. Thus, each meridian has an Exterior-Interior relationship. This Exterior-Interior is not primarily the Biao-Li governed by Taiyin and Taiyang. The Foot Three Yin enter the abdomen from the feet; the Hand Three Yin exit the hands from the abdomen. The Six Yin connect sequentially in the abdomen. The Hand Three Yang travel from hands to head; the Foot Three Yang travel from head to feet. The Six Yang connect sequentially at the head. In the abdomen, Yin connects with Yin; at the head, Yang connects with Yang. At the hands, inner Yin connects with outer Yang; at the feet, outer Yang connects with inner Yin. This is called the tunnel. The parallel courses of the meridians are: In the hand, the Taiyin Lung meridian emerges on the medial upper border of the arm; the Yangming Large Intestine meridian emerges on the lateral upper border; the Shaoyin Heart meridian emerges on the medial lower border; the Taiyang Small Intestine meridian emerges on the lateral lower border; the Jueyin Pericardium meridian emerges on the medial midline of the arm; the Shaoyang Sanjiao meridian emerges on the lateral midline of the arm. The Foot Three Yin and Yang follow similarly. Here, the parallel nature of these tunnels constitutes the concept of Exterior-Interior. Without understanding the substance and function of Zang-Fang Yin-Yang, and without knowing the meridians, one confuses this exterior with that interior, akin to blind men touching an elephant. Therefore, it is necessary to list and record them systematically.