故脉不荣。则筋缩急。筋缩急。即引卵与舌。故舌卷卵缩。此筋先死。庚日笃。辛日死。
足厥阴肝也。肝应乎筋。所以诊肝脉与筋平。肝属木。庚辛属金。木受克。故死也。
手太阴气绝。则皮毛焦。太阴者。肺也。行气温于皮毛者也。气不荣。则皮毛焦。皮毛焦。
则津液去。津液去。则皮节伤。皮节伤。则皮枯毛折。毛折者。则毛先死。丙日笃。丁日死。
手太阴肺也。肺主皮毛。所以诊肺脉与皮毛相得。肺属金。丙丁属火。金受克。故死也。
手少阴气绝。则脉不通。脉不通。则血不流。血不流。则色泽去。故面黑如黧。此血先死。
壬日笃。癸日死。
手少阴心也。心在上而主血。所以诊心脉与血脉相得。心属火。壬癸属水。火受克。故死也
。五行之中。必阳日笃而阴日死。乃见人之生机系乎阳。而命门真阳之义。不可不明也。手厥
阴即心主胞络。与手少阴气绝同。故不另载。
三阴气俱绝。则目眩转目瞑。目瞑者。为失志。失志者。则志先死。死则目暝也。（此三阴
因厥阴同于心脏故不言六阴而六阴在内矣）
前言五脏之气绝。则以五行日干相克之期应之。此言三阴绝。死不待日矣。目眩者。目眩乱而
见不真也。
转者。瞳反也。目瞑则无所见矣。志死则不知喜怒之类也。
六阳气俱绝。则阴与阳相离。阴阳相离。则腠理泄，绝汗乃出。大如贯珠。转出不流。即
气先死。旦占夕死。夕占旦死。
前言三阴绝。死不待日。此言六阳绝。死不待时。乃见阳重于阴。气先死者。即命门真阳
之气先死也。
二十五难曰。有十二经。五脏六腑十一耳。其一经者。何等经也。然。一经者。手少阴与心主别
脉也。（心主即手心主胞络别脉者不同于心经脉也）心主与三焦为表里。俱有名而无形。故言经有
十二也。（胞络配一脏成十二经也）
此章言心主与三焦为表里。俱有名而无形。后人因无形二字。不参经义。持论纷纭，不特议
越人之错谬。
而并议叔和附会之非。三千年来。未有定论。余每思难经去古未远。出诸家之最先。且字字必
本内经。
岂独于胞络三焦大关键处。反创异言而惑世耶。不得不即以内经合难经之义。而明辨之。如内经之
言五脏俱载形色。五腑亦载丈尺。所盛水谷。亦载升斗。若胞络三焦有形。何独不明载其色。并尺
寸升斗之数。乃见难经所言胞络者。以包字取义也。言三焦者。以三字取义也。如灵素本输篇
曰。三焦者。中渎之府。水道出焉。属膀胱。是孤之府。本藏篇曰。密理浓皮。三焦膀胱浓。决
气篇曰。上焦开发。宣五谷味。若雾露之溉。是谓气。中焦受气取汁。变化而赤。是谓血。荣卫
生卫篇曰。荣出于中焦。卫出于下焦。又曰。上焦如雾。
中焦如沤。下焦如渎。五癃津液别论曰。三焦出气。以温肌肉。充皮肤。灵枢邪客篇曰。心者
五脏六腑之大主。其脏坚固。邪勿能容。容之则心伤。心伤则神去而死矣。故谓邪之在于心者。皆
在于心之胞络。以上灵素诸条。俱形容三焦统包五脏六腑。胞络独包心之义。夫所谓中渎之府。
是孤之府。岂非因三焦能包乎外。而得此独尊之称乎。又谓密理浓皮。三焦浓。若周身皮肉之内。非
三焦所托。何能浓薄相应乎。又谓上焦宣谷味。中焦受气取汁。变化而赤。岂非三焦能包各脏腑。
而各脏腑俱藉三焦之气以宣化乎。又谓荣出中焦。卫出下焦。荣因谷味之精为血。卫得谷味之气
为气。皆因于胃者也。然能使胃之变化者。岂非三焦统包乎外。而运其气乎。又谓如雾如沤。
如渎。能上主开发之令。中主变化之权。下主水道之职。
岂非三焦包各脏腑之外。而尽为其统持乎。又谓出气以温肌肉充皮肤。则明指三焦托在皮肤肌肉
里面之一层也。又谓诸邪之在于心者。皆在心之胞络。则明指胞络是护于心外之一层也。后人
看书执着。
将谓三焦若无形。何以水道出。何以有浓薄。何以若雾露。何以如雾如沤如渎。何以出气温肌肉
。若胞络无形。何以诸邪皆在心之胞络。何独不悟夫何以不载其色。何以不载其丈尺乎。殊不知
胞络者。络于内而胞于外之一小囊也。既已名之曰胞络。不必又以大小尺寸状其形也。三焦者。
托于外而护于内之一大囊也。不过三字极状其护之遍。以焦字极状其气之周。既已名之曰三焦。亦
不必又以大小丈尺状其
形也。而向之所疑者。从此可顿释矣。且以似脏别脏之小囊。配似腑外腑之大囊。亦天造地设之
理。（三十四难称焦为外府）越人谓无形二字。一见于此。再见于三十四难。自必考之至当。究之至确。
何后人仅得内经之皮毛。即妄议前贤。多见其不知量也。
二十六难（二十六难次节误列二十七难末节）曰。经有十二。络有十五。余三络者。是何等络也。然。有阳络。有
阴络。有脾之大络。阳络者。阳跷之络也。阴络者。阴跷之络也。故络有十五焉。
此章总论经络以起下文之义。直行谓经。旁支曰络。络有十五。本文自明。
经有十二。络有十五。凡二十七气。相随上下。何独不拘于经也。然。圣人图设沟渠。通利水道。以
备不然。天雨降下。沟渠溢满。当此之时。 霈妄行。圣人不能复图也。此络脉满溢。诸经不能复拘也。
此节误列二十七难之后。文理何由贯通。今录正。更觉丝丝入扣。上文言十五络。此言十二
经。不能拘十五络。故以图设沟渠。喻十二经。圣人不能复图。十二经之气血满溢。归于经络。而不能复令络脉之气血。
反于十二经也。
二十七难（二十七难次节误列二十八难次节）曰。脉有奇经八脉者。不拘于十二经。何谓也。然。有阳维
。有阴维。有阳跷。有阴跷。有冲。有督。有任。有带之脉。凡此八脉者。皆不拘于经。故曰奇经八脉也。
凡此八脉。不受十二经之拘制。与络脉之义同。且十二经俱有脏腑配偶。独此八脉无偶。故
曰奇经。
比于圣人图设沟渠。沟渠满溢。流于深湖。故圣人不能拘通也。而人脉隆盛。入于八脉
。而不还周。故十二经。亦不能拘之。其受邪气。蓄则肿热。砭射之也。（砭贬平声针石也）
此节误列二十八难后。此言十二经亦不能拘八脉。故复以图设沟渠喻十二经。深湖喻八脉。圣人不能拘通者。言十
二经脉之气血隆盛。入于八脉。而不能复令八脉之气血。反于十二经也。故其受邪亦不能通于诸经。所以蓄而为肿
热也。砭射之。出其所蓄之血也。
二十八难曰。其奇经八脉者。既不拘于十二经。皆何起何继也。然。督脉者。起于下极之俞。并于脊里。上至风府。
入属于脑。
此承明八脉起止之义。下极。长强穴也。在脊 骨端。风府穴在脑后发上三寸。盖督者都也。
能统诸阳脉行于背。为阳脉之都纲也。
任脉者。起于中极之下。以上至毛际。循腹里。上关元。至咽喉。上颐循面。入目络舌。
脐下三寸关元穴。任者妊也。能统诸阴脉行于腹。为阴脉之妊养也。
冲脉者。起于气冲。并足阳明之经。挟脐上行。至胸中而散。
气冲。一名气街。穴在毛际两旁。督任脉始于气冲。一原而分三岐。督脉行于背。任脉行于腹。冲则直上。总领诸经
之脉。故曰气海。并于胃之经。挟脐而上行。
带脉者。起于季胁。回身一周。
季胁。章门穴也。在小肋。回身一周。如束带也。
阳跷脉者。起于跟中。循外踝上行入风池。
起自足跟。循足外踝上行入风池穴。其穴在后顶发际陷中。
阴跷脉者。亦起于跟中。循内踝上行至咽喉。交贯冲脉。
交贯冲脉者。与冲脉交接贯通也。
阳维阴维者。维络于身。溢蓄不能环流灌溢诸经者也。故阳维起于诸阳会。阴维起于诸阴交也。
溢蓄不能环流灌溢诸经。即上章入于八脉不还周之义。诸阳会在足外踝骨下陷中。穴名金门。
诸阴交在足内踝上除踝三寸骨陷中。穴名筑宾。
二十九难曰。奇经之为病。何如。然。阳维维于阳。阴维维于阴。阴阳不能自相维。则怅然失志。溶
溶不能自收持。
此章明八脉病情之义。阳维维于阳。谓阳维脉能维络一身之阳脉。阴维维于阴。谓阴维脉能维
络一身之阴脉。若病在二脉。则一身之阳脉阴脉不能自相维，觉神思不快。如怅然失志。四肢
溶溶懈怠。如不能收持也。此言二脉合病。末节言二脉分病。
阴跷为病。阳缓而阴急。
阴跷脉受邪。则阳跷缓纵。阴跷紧急也。阴跷起跟中。循内踝上行。
阳跷为病。阴缓而阳急。
阳跷脉受邪。则阴跷脉缓纵。阳跷脉紧急也。阳跷起跟中。循外踝上行。
冲之为病。逆气而里急。
冲脉起于气冲穴。又名气海。其受邪则气必逆。病必里急而作痛也。其所以受邪。亦因肾气不足。而邪能干之也。
督之为病。脊强而厥。
脊。督脉所过之处也。督脉受邪。病必脊痛而厥逆也。
任之为病。其内苦结。男子七疝。女子瘕聚。
任脉起于中极小腹之下。故其受邪为病。俱在腹内也。
带之为病。腹满。腰溶溶若在水中。
带脉起于季胁。回身如束带。故其受邪为病。在腰腹。若在水中句。解溶溶二字之神理。
阳维为病。苦寒热。
阳维之脉。维络于阳。阳为卫而主表。故其受邪为病。必苦寒热也。
阴维为病。苦心痛。
阴维之脉。维络于阴。阴为荣而主里。荣属血而主心也。其受邪为病。必苦心痛也。然亦有
因寒。亦有因热。此奇经八脉之为病也。
总结上文之意也。以上八脉之邪。大抵风寒湿乘虚集入而为病者居多。不可不察。八脉另列病
因。经脉不能拘故也。
三十难（误列三十二难）曰。五脏俱等。而心肺独在膈上者何也。然。心者血。肺者气。血为
荣。气为卫。相随
上下。（血气相随周行身上下）谓之荣卫。通行经络。（荣行脉中卫行脉外）荣周于身。故令心
肺在膈上也。
此谓心肺乃气血之主。故居膈上。以别气血为荣卫。周于身者出也。下章详言荣卫之源。
三十一难（误列三十难）曰。荣气之行。常与卫气相随不。然。经言人受气于谷。谷入于胃。乃传于肺。五脏
六腑皆受于气。其清者为荣。浊者为卫。荣行脉中。卫行脉外。荣周不息。五十而后大会。阴阳
利贯。（利贯流利而贯通）如环之无端。故知荣卫相随也。
此言荣卫相随不息之源。起于胃之谷气。其清者为荣。即谷味之精。乃阳中之阴。化血为荣
。行于脉中。其浊者为卫。即谷味之气。乃阴中之阳。化气为卫。行于脉外。荣卫相随。周行脏
腑之经脉。一日夜行五十度。
复会于手太阴寸口。荣卫生会篇曰。荣出中焦。卫出下焦。
三十二难（误列三十一难）曰。三焦者。何禀何生。何始何终。其治常在何许。可晓以不。然。
三焦者。水谷之道路。气之所终始也。
此言三焦裹于胃之水谷。生于下文各属之穴。终始不息也。
上焦者。在心下之膈。在胃上口。主纳而不出。其治在膻中。玉堂下一寸六分。直两乳间陷下底
是。中焦者。在胃中。不上不下。腐熟水谷。其治在脐旁。下焦者。在脐下。当膀胱上口。主
分别清
浊。主出而不纳。以传导也。其治在脐下一寸。故名曰三焦。其腑在气卫。（府犹根也气卫即气
卫也此即三焦之源也）
此节本文自明。膻中玉堂穴。经穴篇详载治属也。
三十三难曰。肝青属木。肺白属金。肝得水而沉。木得水而浮。肺得水而浮。金得水而沉。
其意何也。然。肝者。非为纯木也。乙角也。庚之柔。大言阴与阳。小言夫与妇。释其微阳。而
吸其微阴之气。其意乐。金又行阴道多。（庚金居阴道）故令肝得水而沉也。非为纯金也。辛商
也。丙之柔。大言阴与阳。小言夫与妇。释其微阴。婚而就火。其意乐。火又行阳道多。（丙
火居阳道）故肺得水而浮也。
此章言阴阳互根。五行交合之理。凡人身不外乎阴阳。交则生。不交则病。离则死。越人特
举肝肺而言者。肝主血。而肺主气。此又以气血为一身阴阳之主也。学人既透此章之义。则前后
八十一难之经义。无不可以神会而贯也。即五行之理。无非在阴阳交合。如天干甲乙丙丁戊为阳
道。己庚辛壬癸为阴道。此十干对分而为交合之阴阳也。又甲乙木。丙丁火。戊己土庚辛金。壬癸
水。上一字属阳属阴。此五行各分。为交合之阴阳也。又五音。附五行。如宫土商金角木征火
羽水。各因十干之阴阳。而分大小。此五音附十干而为交合之阴阳也。又人之五脏属阴行。而其
中之文合。又寓阳五行。此脏腑各有交合之阴阳也。明乎阴阳交合之义。然后可以畅达此章之理
矣。如经云。肝非纯木。乙角也。庚之柔。言肝乃乙
角之阴木也。然又非纯木。乙与庚合。故其中寓庚金。庚属阳而乙属阴。故乙木乃庚金之柔也
。大而言之。即阴与阳。小而言之。如夫与妇也。又云。释其微阳。而吸其微阴之气。其意乐。释犹
开也。吸犹收也。乙木。二月之木也。阳气未盛。故曰微阳。庚金。七月之金也。七月阴气未盛
因此，脉气不能滋养筋脉，就会导致筋脉收缩拘急。筋脉收缩拘急，就会牵引睾丸和舌头。所以出现舌头卷缩、睾丸上提的症状。这是筋脉先死的表现，在庚日病情加重，在辛日死亡。
足厥阴经属于肝。肝主管筋脉，所以诊察肝脉要与筋脉的状态相平合。肝属木，庚、辛属金。木受到金的克制，所以死亡。
手太阴经的气绝，会导致皮毛枯焦。手太阴经就是肺。肺运行气并温煦皮毛。气不能滋养，就会导致皮毛枯焦。皮毛枯焦，津液就会耗散。津液耗散，皮节就会受损。皮节受损，皮肤干枯、毛发折断。毛发折断，说明毛发先死。在丙日病情加重，在丁日死亡。
手太阴经就是肺。肺主管皮毛，所以诊察肺脉要与皮毛的状态相符。肺属金，丙、丁属火。金受到火的克制，所以死亡。
手少阴经的气绝，会导致脉道不通。脉道不通，血液就不能流动。血液不流动，面色光泽就会消失。所以面色黑得像黑炭一样。这是血液先死的表现。在壬日病情加重，在癸日死亡。
手少阴经就是心。心位于上部且主管血液，所以诊察心脉要与血脉的状态相符。心属火，壬、癸属水。水受到火的克制（注：原文逻辑为火受水克，但此处原文写“火受克”，结合上下文五行相克原理，应为水克火，即壬癸水克丙丁火，但原文表述为“火受克”可能指代被克制的状态或笔误，依原文直译），所以死亡。
在五行之中，一定是阳日病情加重而阴日死亡，这显示出人的生机系于阳气，而命门真阳的意义，不可不明确。手厥阴经即心主包络，与手少阴经气绝的情况相同，所以不再单独记载。
三阴经的气都绝，会导致头晕眼花、视物旋转、眼睛闭合。眼睛闭合，是因为神志丧失。神志丧失，说明神志先死。神志死了，眼睛就会闭合。（这三阴经因为厥阴经与心脏关系密切，所以不说六阴经而六阴经包含在内了）
前面讲五脏之气绝，是用五行日干相克的日期来应验。这里讲三阴经气绝，死亡就不等待日期了。目眩，是指头晕眼花、视物不清。
转，是指瞳孔反视。眼睛闭合就什么也看不见了。神志死了，就不知道喜怒等情绪了。
六阳经的气都绝，会导致阴与阳分离。阴阳分离，腠理就会开泄，绝汗就会流出。汗水大如连珠，转动流出但不流淌，这就是气先死。早上占测晚上死，晚上占测早上死。
前面讲三阴经气绝，死亡不等待日期。这里讲六阳经气绝，死亡不等待时辰，这显示出阳气重于阴气。气先死的，就是命门真阳之气先死。
第二十五难说：有十二经脉，五脏六腑只有十一个。那多出来的一经，是什么经呢？回答说：多出来的一经，是手少阴经与心主别脉。（心主即手心主包络的别脉，不同于心经脉本身）心主与三焦互为表里，都有名而没有形质。所以说经脉有十二条。（包络配一脏成为十二经脉）
这一章讲心主与三焦互为表里，都有名而没有形质。后人因为“无形”二字，不参究经络的本义，持论纷纷，不仅议论越人（扁鹊）的错误，还一并议论叔和（王叔和）附会的非议。三千年来，没有定论。我每次思考，《难经》距离古代不远，出自各家著作之最先，而且字字必本于《内经》，难道唯独在包络和三焦这个关键地方，反而创制异言来迷惑世人吗？不得不即用《内经》结合《难经》的意义，来明辨它。比如《内经》讲五脏都记载颜色和形状，五腑也记载尺寸，所容纳的水谷，也记载升斗数。如果包络和三焦有形，为什么唯独不明确记载其颜色，以及尺寸升斗的数目呢？这就看出《难经》所说的包络，是以“包”字取义；所说的三焦，是以“三”字取义。比如《灵枢·本输篇》说：三焦是中渎之府，水道出于此，归属于膀胱，是孤之府。《本藏篇》说：纹理致密、皮肤厚的人，三焦和膀胱的膜也厚。《决气篇》说：上焦开发，宣发五谷的味道，像雾露灌溉一样，这叫气。中焦接受气并汲取汁液，变化而变红，这叫血。《营卫生会篇》说：营气出于中焦，卫气出于下焦。又说：上焦如雾，中焦如沤，下焦如渎。《五癃津液别论》说：三焦出气，以温养肌肉，充实皮肤。《灵枢·邪客篇》说：心是五脏六腑的大主，它的脏坚固，邪气不能容纳。如果容纳了就会伤心，心伤就会神去而死。所以说邪气在于心的，都在于心的包络。以上《灵枢》、《素问》的各条经文，都在形容三焦统包五脏六腑，包络独包心的意义。所谓中渎之府，是孤之府，难道不是因为三焦能包乎外，而得到这种独尊的称号吗？又说纹理致密、皮肤厚，三焦膜也厚，如果周身皮肉之内，不是三焦所托举，怎么能厚薄相应呢？又说上焦宣发谷味，中焦受气取汁，变化而赤，难道不是三焦能包各脏腑，而各脏腑都借助三焦之气来宣化吗？又说营出中焦，卫出下焦，营因谷味的精微化为血，卫得谷味的气化为气，都源于胃。然而能使胃发生变化的，难道不是三焦统包乎外，而运化其气吗？又说像雾、像沤、像渎，能上主开发之令，中主变化之权，下主水道之职，难道不是三焦包各脏腑之外，而尽为其统持吗？又说出气以温肌肉充皮肤，则明确指向三焦托在皮肤肌肉里面的一层。又说诸邪之在于心者，皆在心之包络，则明确指向包络是护于心外的一层。后人看书执着，认为如果三焦无形，为什么有水道出？为什么有厚薄？为什么像雾露？为什么如雾如沤如渎？为什么出气温肌肉？如果包络无形，为什么诸邪皆在心之包络？为什么不悟为何不记载其颜色？为什么不记载其尺寸呢？殊不知包络，是络于内而胞于外的一小囊。既然名叫包络，不必再用大小尺寸来描述其形状。三焦，是托于外而护于内的一大囊。不过是“三”字极状其护之遍，“焦”字极状其气之周。既然名叫三焦，也不必再用大小尺寸来描述其形状。而先前所疑惑的，从此可以顿时释然。且以似脏别脏的小囊，配似腑外腑的大囊，也是天造地设的道理。（第三十四难称焦为外府）越人说“无形”二字，一见于此，再见见于第三十四难，自然必考之至当，究之至确。为何后人仅得《内经》的皮毛，就妄议前贤，多见其不知量也。
第二十六难（第二十六难次节误列在二十七难末节）说：经脉有十二条，络脉有十五条。那多余的三条络脉，是什么络脉呢？回答说：有阳络，有阴络，有脾之大络。阳络，是阳跷的络脉。阴络，是阴跷的络脉。所以络脉有十五条。
这一章总论经络以引起下文的意思。直行叫经，旁支叫络。络脉有十五条，本文自明。
经脉有十二条，络脉有十五条，共二十七气，相随上下，为什么唯独不拘限于经脉呢？回答说：圣人规划设置沟渠，通利水道，以备不测。天雨降下，沟渠溢满，在这个时候，雨水泛滥妄行，圣人也不能再规划了。这也是络脉满溢，诸经不能再拘束它了。
这一节误列在第二十七难之后，文理如何贯通？现在记录校正后，更觉得丝丝入扣。上文讲十五络，这里讲十二经，不能拘束十五络，所以用图设沟渠比喻十二经。圣人不能复图，指十二经的气血满溢，归于经络，而不能复令络脉的气血反于十二经。
第二十七难（第二十七难次节误列在二十八难次节）说：脉有奇经八脉，不拘于十二经，是什么意思呢？回答说：有阳维，有阴维，有阳跷，有阴跷，有冲，有督，有任，有带脉。凡这八脉，都不拘束于经脉，所以叫奇经八脉。
凡这八脉，不受十二经的拘制，与络脉的意义相同。而且十二经都有脏腑配偶，唯独这八脉没有配偶，所以叫奇经。
比于圣人规划设置沟渠，沟渠满溢，流于深湖，所以圣人不能拘束通利。而人脉隆盛，流入八脉，而不返还循环，所以十二经也不能拘束它。它们受邪气，蓄积则肿热，用砭石刺破放出。（砭，贬平声，针石）
这一节误列在第二十八难后。这里讲十二经也不能拘束八脉，所以再次用图设沟渠比喻十二经，深湖比喻八脉。圣人不能拘通，指十二经脉的气血隆盛，流入八脉，而不能复令八脉的气血反于十二经。所以它们受邪也不能通于诸经，因此蓄积而为肿热。砭射，是放出其所蓄积的血。
第二十八难说：那奇经八脉，既然不拘于十二经，都是从哪里起始、到哪里接续的呢？回答说：督脉，起于下极的俞穴，并行于脊里，上至风府，入属于脑。
这是承接阐明八脉起止的意义。下极，是长强穴。在脊椎骨端。风府穴在脑后发上三寸。盖“督”就是“都”，能统率诸阳脉行于背，为阳脉的都纲。
任脉，起于中极之下，以上至毛际，循腹里，上关元，至咽喉，上颐循面，入目络舌。
脐下三寸是关元穴。“任”就是“妊”，能统率诸阴脉行于腹，为阴脉的妊养。
气冲，一名气街。穴在毛际两旁。督任脉始于气冲，一原而分三岐。督脉行于背，任脉行于腹，冲脉则直上，总领诸经之脉，所以叫气海。并于胃之经，挟脐而上行。
带脉，起于季胁，回身一周。
季胁，是章门穴。在小肋。回身一周，如束带。
阳跷脉，起于跟中，循外踝上行入风池。
起自足跟，循足外踝上行入风池穴。其穴在后顶发际陷中。
阳维、阴维，维络于身，溢蓄不能环流灌溢诸经者也。所以阳维起于诸阳会，阴维起于诸阴交。
溢蓄不能环流灌溢诸经，即上一章“入于八脉不还周”的意义。诸阳会在足外踝骨下陷中，穴名金门。诸阴交在足内踝上除踝三寸骨陷中，穴名筑宾。
第二十九难说：奇经之为病，怎么样呢？回答说：阳维维于阳，阴维维于阴，阴阳不能自相维，则怅然失志，溶溶不能自收持。
这一章阐明八脉病情的意义。阳维维于阳，谓阳维脉能维络一身之阳脉。阴维维于阴，谓阴维脉能维络一身之阴脉。若病在二脉，则一身之阳脉阴脉不能自相维，觉神思不快，如怅然失志，四肢溶溶懈怠，如不能收持。此言二脉合病，末节言二脉分病。
阳跷脉受邪，则阴跷脉缓纵，阳跷脉紧急。阳跷起跟中，循外踝上行。
冲脉起于气冲穴，又名气海。其受邪则气必逆，病必里急而作痛。其所以受邪，亦因肾气不足，而邪能干之。
任脉起于中极小腹之下，故其受邪为病，俱在腹内。
带脉起于季胁，回身如束带。故其受邪为病，在腰腹。“若在水中”句，解“溶溶”二字之神理。
阴维之脉，维络于阴。阴为荣而主里，荣属血而主心。其受邪为病，必苦心痛。然亦有因寒，亦有因热。此奇经八脉之为病也。
总结上文之意。以上八脉之邪，大抵风寒湿乘虚集入而为病者居多，不可不察。八脉另列病因，经脉不能拘故也。
第三十难（误列三十二难）说：五脏俱等，而心肺独在膈上者何也？回答说：心是血，肺是气。血为荣，气为卫，相随上下。（血气相随周行身上下）谓之荣卫。通行经络。（荣行脉中卫行脉外）荣周于身，所以令心肺在膈上也。
此谓心肺乃气血之主，故居膈上，以别气血为荣卫，周于身者出也。下一章详言荣卫之源。
第三十一难（误列三十难）说：荣气之行，常与卫气相随不？回答说：经言人受气于谷，谷入于胃，乃传于肺，五脏六腑皆受于气。其清者为荣，浊者为卫。荣行脉中，卫行脉外。荣周不息，五十而后大会。阴阳利贯。（利贯流利而贯通）如环之无端。故知荣卫相随也。
此言荣卫相随不息之源，起于胃之谷气。其清者为荣，即谷味之精，乃阳中之阴，化血为荣，行于脉中。其浊者为卫，即谷味之气，乃阴中之阳，化气为卫，行于脉外。荣卫相随，周行脏腑之经脉，一日夜行五十度，复会于手太阴寸口。《营卫生会篇》说：荣出中焦，卫出下焦。
第三十二难（误列三十一难）说：三焦者，何禀何生？何始何终？其治常在何许？可晓以不？回答说：三焦者，水谷之道路，气之所终始也。
上焦者，在心下之膈，在胃上口，主纳而不出。其治在膻中，玉堂下一寸六分，直两乳间陷下底是。中焦者，在胃中，不上不下，腐熟水谷。其治在脐旁。下焦者，在脐下，当膀胱上口，主分别清浊，主出而不纳，以传导也。其治在脐下一寸，故名曰三焦。其腑在气卫。（府犹根也，气卫即气卫也，此即三焦之源也）
第三十三难说：肝青属木，肺白属金。肝得水而沉，木得水而浮。肺得水而浮，金得水而沉。其意何也？回答说：肝者，非为纯木也。乙角也，庚之柔。大言阴与阳，小言夫与妇。释其微阳，而吸其微阴之气。其意乐，金又行阴道多。（庚金居阴道）故令肝得水而沉也。肺者，非为纯金也。辛商也，丙之柔。大言阴与阳，小言夫与妇。释其微阴，婚而就火。其意乐，火又行阳道多。（丙火居阳道）故肺得水而浮也。
这一章讲阴阳互根、五行交合之理。凡人身不外乎阴阳，交则生，不交则病，离则死。越人特举肝肺而言者，肝主血，而肺主气，此又以气血为一身阴阳之主也。学人既透此章之义，则前后八十一难之经义，无不可以神会而贯也。即五行之理，无非在阴阳交合。如天干甲乙丙丁戊为阳道，己庚辛壬癸为阴道，此十干对分而为交合之阴阳也。又甲乙木，丙丁火，戊己土，庚辛金，壬癸水，上一字属阳属阴，此五行各分，为交合之阴阳也。又五音，附五行，如宫土、商金、角木、征火、羽水，各因十干之阴阳，而分大小，此五音附十干而为交合之阴阳也。又人之五脏属阴行，而其中的文合，又寓阳五行，此脏腑各有交合之阴阳也。明乎阴阳交合之义，然后可以畅达此章之理矣。如经云：肝非纯木，乙角也，庚之柔。言肝乃乙角之阴木也。然又非纯木，乙与庚合，故其中寓庚金。庚属阳而乙属阴，故乙木乃庚金之柔也。大而言之，即阴与阳；小而言之，如夫与妇也。又云：释其微阳，而吸其微阴之气，其意乐。释犹开也，吸犹收也。乙木，二月之木也，阳气未盛，故曰微阳。庚金，七月之金也，七月阴气未盛
Therefore, when the pulse qi fails to nourish the sinews (tendons), it leads to contraction and spasm of the sinews. Contraction and spasm of the sinews will then pull on the testicles and the tongue. Thus, there is curling of the tongue and retraction of the testicles. This indicates that the sinews are dying first; the condition worsens on Geng days and death occurs on Xin days.
The Foot Jueyin meridian belongs to the Liver. The Liver governs the sinews, so palpating the Liver pulse should correspond with the state of the sinews. The Liver belongs to Wood, while Geng and Xin belong to Metal. Since Wood is controlled by Metal, death ensues.
When the Qi of the Hand Taiyin meridian ceases, the skin and hair become scorched and dry. The Hand Taiyin meridian is the Lung. The Lung circulates Qi and warms the skin and hair. When Qi fails to nourish, the skin and hair become scorched and dry. Scorched and dry skin and hair lead to the loss of body fluids. Loss of body fluids damages the skin joints. Damage to the skin joints results in dry skin and broken hair. Broken hair indicates that the hair is dying first; the condition worsens on Bing days and death occurs on Ding days.
The Hand Taiyin meridian is the Lung. The Lung governs the skin and hair, so palpating the Lung pulse should correspond with the state of the skin and hair. The Lung belongs to Metal, while Bing and Ding belong to Fire. Since Metal is controlled by Fire, death ensues.
When the Qi of the Hand Shaoyin meridian ceases, the vessels become obstructed. Obstruction of the vessels leads to stagnation of blood. Stagnation of blood causes the loss of luster in the complexion. Thus, the face becomes black like charcoal. This indicates that blood is dying first; the condition worsens on Ren days and death occurs on Gui days.
The Hand Shaoyin meridian is the Heart. The Heart is located superiorly and governs blood, so palpating the Heart pulse should correspond with the state of the blood vessels. The Heart belongs to Fire, while Ren and Gui belong to Water. Since Fire is controlled by Water, death ensues.
Among the Five Elements, it is always the Yang day that sees worsening of the condition and the Yin day that sees death. This reveals that human vitality depends on Yang Qi, and thus the significance of the True Yang of the Mingmen (Gate of Life) must be clearly understood. The Hand Jueyin meridian is the Pericardium (Pericardium Collateral), which shares the same condition of Qi cessation as the Hand Shaoyin meridian; therefore, it is not recorded separately.
When the Qi of the Three Yin meridians all ceases, dizziness and vertigo occur, and the eyes close. Closing of the eyes signifies the loss of Zhi (Will/Spirit). Loss of Zhi indicates that the Will is dying first. When the Will dies, the eyes close. (These Three Yin meridians are considered together with Jueyin due to its connection with the Heart, so the Six Yin meridians are implied.)
Previously, it was stated that when the Qi of the Five Zang organs ceases, it corresponds to the period of mutual control among the Five Elements and the Heavenly Stems. Here, it is stated that when the Qi of the Three Yin meridians ceases, death does not wait for specific days. "Xuan" (dizziness/vertigo) refers to visual confusion and inability to see clearly.
"Zhuan" (turning) refers to the reversal of the pupils. When the eyes close, one cannot see anything. When the Will dies, one loses awareness of emotions such as joy and anger.
When the Qi of the Six Yang meridians all ceases, Yin and Yang separate. Separation of Yin and Yang leads to the opening of the couli (pores) and the emergence of Ji Han (extreme sweat). The sweat drops are large like beads, rolling out but not flowing. This indicates that Qi is dying first. If observed in the morning, death comes in the evening; if observed in the evening, death comes in the morning.
Previously, it was stated that when the Three Yin meridians cease, death does not wait for days. Here, it is stated that when the Six Yang meridians cease, death does not wait for hours. This reveals that Yang is heavier than Yin. The one whose Qi dies first is the True Yang Qi of the Mingmen.
Difficulty 25 states: There are twelve Jing meridians, but only eleven Zang-Fu organ pairs. Which meridian is the extra one? The answer is: The extra meridian is the distinct collateral of the Hand Shaoyin and the Heart Master (Pericardium). (The Heart Master refers to the distinct collateral of the Hand Jueyin Pericardium, which is different from the Heart meridian itself.) The Heart Master and the Sanjiao (Triple Burner) are exterior-interior paired. Both have names but no form. Therefore, it is said there are twelve meridians. (The Pericardium paired with one Zang forms the twelve meridians.)
This chapter discusses how the Heart Master and Sanjiao are exterior-interior paired, both having names but no form. Later scholars, focusing on the phrase "no form," failed to investigate the true meaning of meridians, leading to controversial theories. They not only criticized Yuèrén (Bian Que) for errors but also accused Shuhe (Wang Shuhe) of forced interpretations. For three thousand years, there has been no definitive conclusion. I often reflect that *Nan Jing* is close to antiquity, originating before other works, and every character is based on *Nei Jing*. Would it create strange words specifically at the critical points of the Pericardium and Sanjiao to confuse the world? I must use the combined meanings of *Nei Jing* and *Nan Jing* to clarify this. For instance, *Nei Jing* records the color and shape of the five Zang organs, and the dimensions and capacity of the five Fu organs. If the Pericardium and Sanjiao had form, why are their colors and dimensions not explicitly recorded? This shows that *Nan Jing* uses "Bao" (wrap/envelop) to define the Pericardium, and "San" (three) to define the Sanjiao. For example, *Ling Shu · Ben Shu* states: "The Sanjiao is the Fu organ of middle channels; water pathways emerge from it, connecting to the Bladder; it is the solitary Fu organ." *Ben Cang* states: "In those with dense skin and thick flesh, the Sanjiao and Bladder membranes are also thick." *Jue Qi* states: "The Upper Jiao opens and disseminates, spreading the flavors of grains like mist and dew; this is called Qi. The Middle Jiao receives Qi and extracts essence, transforming it into redness; this is called Blood." *Ying Wei Sheng Hui* states: "Ying (Nutritive) Qi emerges from the Middle Jiao, Wei (Defensive) Qi emerges from the Lower Jiao." It also says: "The Upper Jiao is like mist, the Middle Jiao like fermentation, the Lower Jiao like a ditch." *Wu Long Jin Ye Bie Lun* states: "The Sanjiao emits Qi to warm the muscles and fill the skin." *Ling Shu · Xie Ke* states: "The Heart is the great master of the five Zang and six Fu. Its substance is solid, so evil cannot enter. If it enters, the Heart is injured, Shen (Spirit) departs, and death follows. Therefore, evil affecting the Heart actually affects the Pericardium of the Heart." All these passages from *Ling Shu* and *Su Wen* describe the Sanjiao as enveloping the five Zang and six Fu, and the Pericardium as exclusively enveloping the Heart. The term "solitary Fu organ" implies that because the Sanjiao envelops externally, it holds a unique status. The statement about thick membranes implies that without the Sanjiao supporting the internal organs, how could the thickness of the skin and muscles correspond? The statements about the Upper Jiao disseminating grain flavors and the Middle Jiao transforming essence imply that the Sanjiao envelops each organ, allowing them to utilize Sanjiao Qi for transformation. The statements about Ying emerging from the Middle Jiao and Wei from the Lower Jiao, both derived from stomach digestion, imply that the Sanjiao envelops externally and moves Qi to facilitate gastric transformation. The metaphors of mist, fermentation, and ditches indicate that the Sanjiao governs opening above, transformation in the middle, and water pathways below, enveloping all organs and maintaining them. The statement about emitting Qi to warm muscles points to the Sanjiao being a layer inside the skin and muscles. The statement about evil affecting the Pericardium points to the Pericardium being a protective layer outside the Heart. Later scholars, being rigid, ask: If Sanjiao has no form, how can there be water pathways, thickness variations, or descriptions like mist/ditch? If the Pericardium has no form, how can evil affect it? Why do they not realize why color and dimensions are not recorded? In fact, the Pericardium is a small sac connecting internally and enclosing externally. Since it is named Pericardium, there is no need to describe its size. The Sanjiao is a large sac supporting externally and protecting internally. "San" describes its comprehensive protection, and "Jiao" describes the circulation of its Qi. Since it is named Sanjiao, there is no need to describe its size. Thus, previous doubts are resolved. Pairing the small sac resembling a Zang with the large sac resembling a Fu is a natural principle. (Difficulty 34 calls Jiao the 'Outer Fu'.) Yuèrén's mention of "no form" appears here and in Difficulty 34, requiring thorough verification. Why do later scholars, grasping only the superficial aspects of *Nei Jing*, rashly criticize ancient sages, showing their lack of self-awareness?
Difficulty 26 (the second part of which is mistakenly listed at the end of Difficulty 27) states: There are twelve Jing meridians and fifteen Luo collaterals. What are the remaining three Luo collaterals? The answer is: There are Yang Luo, Yin Luo, and the Great Luo of the Spleen. The Yang Luo is the collateral of the Yang Qiao vessel. The Yin Luo is the collateral of the Yin Qiao vessel. Thus, there are fifteen Luo collaterals.
This chapter generally introduces the topic of meridians and collaterals to lead into the following text. Straight paths are called Jing; branches are called Luo. The text clearly states there are fifteen Luo collaterals.
There are twelve Jing meridians and fifteen Luo collaterals, totaling twenty-seven Qi, moving up and down together. Why are they not strictly confined to the meridians? The answer is: Sages dug canals to facilitate water flow for emergencies. When rain falls and canals overflow, floodwaters spread wildly, and even sages cannot control them. Similarly, when Luo collaterals are full and overflowing, the main meridians cannot restrain them.
This section was mistakenly placed after Difficulty 27, disrupting the logic. Correcting it reveals tight coherence. The previous text discussed fifteen Luo collaterals; this text discusses twelve Jing meridians. Since the fifteen Luo collaterals cannot be constrained, the metaphor of digging canals illustrates the twelve Jing meridians. Just as sages cannot control overflowing canals, when the Qi and Blood of the twelve Jing meridians overflow into the collaterals, they cannot return to the main meridians.
Difficulty 27 (the second part of which is mistakenly listed in the second part of Difficulty 28) states: There are eight Extraordinary Vessels in the pulse, which are not confined to the twelve Jing meridians. What does this mean? The answer is: There are Yang Wei, Yin Wei, Yang Qiao, Yin Qiao, Chong, Du, Ren, and Dai meridians. These eight vessels are not confined to the main meridians, hence called the Eight Extraordinary Vessels.
These eight vessels are not restricted by the twelve Jing meridians, similar to the nature of Luo collaterals. Unlike the twelve Jing meridians, which have paired Zang-Fu organs, these eight vessels have no partners, hence called "Extraordinary" (Qi).
Comparing this to sages digging canals: when canals overflow, water flows into deep lakes, which sages cannot regulate. Similarly, when human pulse Qi is abundant, it enters the eight extraordinary vessels and does not circulate back, so the twelve Jing meridians cannot constrain them. When these vessels receive pathogenic factors, accumulation leads to swelling and heat, treated by Bian stone puncture. (Bian refers to stone needles.)
This section was mistakenly placed after Difficulty 28. It explains that the twelve Jing meridians cannot constrain the eight extraordinary vessels, using the canal/lake metaphor again. Sages cannot regulate the lake means that abundant Qi in the twelve meridians flows into the eight vessels and cannot return. Thus, pathogens accumulate there causing swelling and heat, treated by releasing the accumulated blood via Bian stone.
Difficulty 28 states: Since the Eight Extraordinary Vessels are not confined to the twelve Jing meridians, where do they originate and where do they connect? The answer is: The Du Meridian originates at the Xiaji acupoint, runs parallel to the spine, ascends to the Fengfu acupoint, and enters the brain.
This continues the explanation of the origin and termination of the eight vessels. Xiaji is the Changqiang acupoint, at the end of the vertebral column. Fengfu is three cun above the posterior hairline. "Du" means "capital"; it governs all Yang meridians running along the back, serving as the chief guideline for Yang meridians.
The Ren Meridian originates below Zhongji, ascends to the pubic hairline, runs along the interior of the abdomen, passes through Guanyuan, reaches the throat, goes up over the chin, follows the face, enters the eyes, and connects to the tongue.
Guanyuan is three cun below the umbilicus. "Ren" means "pregnancy/nourishment"; it governs all Yin meridians running along the abdomen, serving as the nourisher for Yin meridians.
The Chong Meridian originates at Qichong, runs alongside the Foot Yangming meridian, flanks the umbilicus upwards, and disperses in the chest.
Qichong, also known as Qijie, is located on both sides of the pubic hairline. The Du and Ren meridians originate from Qichong, branching from one source into three. The Du runs along the back, the Ren along the abdomen, and the Chong goes straight up, governing all meridians, hence called Qihai. It runs alongside the Stomach meridian, flanking the umbilicus upwards.
The Dai Meridian originates at the Flank (Ji Xie), encircling the body once.
The flank is the Zhangmen acupoint, located at the lower ribs. Encircling the body once, it resembles a belt.
The Yang Qiao Meridian originates in the heel, runs along the lateral malleolus upwards, and enters the Fengchi acupoint.
It starts at the heel, runs along the lateral aspect of the foot and ankle, and enters Fengchi, located in the depression at the upper hairline of the occiput.
The Yin Qiao Meridian also originates in the heel, runs along the medial malleolus upwards to the throat, and intersects with the Chong Meridian.
Intersecting with the Chong Meridian means connecting and communicating with it.
Yang Wei and Yin Wei networks the body; when they overflow and accumulate, they cannot circulate and irrigate the main meridians. Therefore, Yang Wei originates at the meeting of all Yang meridians, and Yin Wei originates at the intersection of all Yin meridians.
Overflowing and accumulating without circulating back to the main meridians is the same meaning as "entering the eight vessels and not returning" mentioned earlier. The meeting of all Yang meridians is in the depression below the lateral malleolus, the Jinmen acupoint. The intersection of all Yin meridians is in the bone depression three cun above the medial malleolus, the Zhubin acupoint.
Difficulty 29 states: What are the diseases of the Extraordinary Vessels? The answer is: Yang Wei networks Yang, Yin Wei networks Yin. If Yin and Yang cannot network each other, there is melancholy and loss of will, and a feeling of limpness and inability to control oneself.
This chapter clarifies the pathology of the eight vessels. Yang Wei networking Yang means it networks all Yang meridians of the body. Yin Wei networking Yin means it networks all Yin meridians. Disease in these two vessels causes the body's Yin and Yang meridians to fail to support each other, resulting in mental discomfort, feeling lost, and limbs feeling limp and unable to hold themselves. This describes combined disease of the two vessels; the final section describes separate disease.
Disease of Yin Qiao presents with slackness of Yang and tension of Yin.
When Yin Qiao is affected by pathogens, Yang Qiao becomes slack and Yin Qiao becomes tense. Yin Qiao originates in the heel and runs along the medial malleolus upwards.
Disease of Yang Qiao presents with slackness of Yin and tension of Yang.
When Yang Qiao is affected by pathogens, Yin Qiao becomes slack and Yang Qiao becomes tense. Yang Qiao originates in the heel and runs along the lateral malleolus upwards.
Disease of Chong presents with rebellious Qi and abdominal urgency/pain.
Chong originates at Qichong, also called Qihai. When affected by pathogens, Qi rebels, causing abdominal urgency and pain. This occurs due to deficiency of Kidney Qi, allowing pathogens to invade.
Disease of Du presents with stiffness of the spine and cold extremities.
The spine is the pathway of the Du Meridian. When Du is affected by pathogens, it causes spinal pain and cold extremities.
Disease of Ren presents with internal knotting, seven types of hernia in men, and masses in women.
Ren originates below Zhongji in the lower abdomen, so its diseases manifest internally in the abdomen.
Disease of Dai presents with abdominal fullness and a sensation of the waist being limp as if in water.
Dai originates at the flank and encircles the body like a belt. Its diseases manifest in the waist and abdomen. "As if in water" explains the spirit of the word "Rong Rong" (limp/flaccid).
Disease of Yang Wei presents with aversion to cold and fever.
Yang Wei networks Yang. Yang represents Wei (Defensive) Qi and governs the exterior. Thus, when affected by pathogens, it causes aversion to cold and fever.
Disease of Yin Wei presents with heart pain.
Yin Wei networks Yin. Yin represents Ying (Nutritive) Qi and governs the interior. Ying belongs to Blood and governs the Heart. Thus, when affected by pathogens, it causes heart pain. However, this can be due to Cold or Heat. These are the diseases of the Eight Extraordinary Vessels.
This summarizes the preceding text. Most diseases of these eight vessels are caused by Wind, Cold, and Dampness invading due to deficiency, which must be carefully observed. The eight vessels list separate etiologies because they are not constrained by the main meridians.
Difficulty 30 (mistakenly listed as 32) states: The five Zang organs are equal, yet the Heart and Lung alone are above the diaphragm. Why? The answer is: The Heart is Blood, the Lung is Qi. Blood is Ying, Qi is Wei. They move up and down together (circulating throughout the body). This is called Ying and Wei. They circulate through the meridians (Ying moves within vessels, Wei moves outside vessels). Ying circulates throughout the body, hence the Heart and Lung are located above the diaphragm.
This means the Heart and Lung are the masters of Qi and Blood, residing above the diaphragm to distinguish Ying and Wei, which circulate throughout the body. The next chapter details the source of Ying and Wei.
Difficulty 31 (mistakenly listed as 30) states: Does Ying Qi always move with Wei Qi? The answer is: The classics state that humans receive Qi from grain. Grain enters the Stomach, transmits to the Lung, and nourishes all five Zang and six Fu organs. The clear portion becomes Ying, the turbid portion becomes Wei. Ying moves within the vessels, Wei moves outside. Ying circulates endlessly, meeting every fifty cycles. Yin and Yang flow smoothly like a circle without end. Thus, we know Ying and Wei move together.
This explains the continuous source of Ying and Wei, starting from grain Qi in the Stomach. The clear portion is Ying, the essence of grain flavor, Yin within Yang, transforming into Blood, moving within vessels. The turbid portion is Wei, the Qi of grain flavor, Yang within Yin, transforming into Qi, moving outside vessels. Ying and Wei move together, circulating through the meridians of the Zang and Fu, completing fifty cycles in one day and night, meeting again at the Cunkou point of the Hand Taiyin. *Ying Wei Sheng Hui* states: "Ying emerges from the Middle Jiao, Wei emerges from the Lower Jiao."
Difficulty 32 (mistakenly listed as 31) states: From what does the Sanjiao inherit and arise? Where does it start and end? Where is its treatment located? Can this be explained? The answer is: The Sanjiao is the pathway for water and grain, and the beginning and end of Qi.
This states that Sanjiao wraps around water and grain in the Stomach, arises from the acupoints belonging to it below, and ends continuously.
The Upper Jiao is at the diaphragm below the Heart, at the upper opening of the Stomach. It governs reception but not excretion. Its treatment point is Danzhong, one cun and six fen below Yutang, directly between the nipples in the depression. The Middle Jiao is in the Stomach, neither rising nor falling, rotting and ripening water and grain. Its treatment point is beside the umbilicus. The Lower Jiao is below the umbilicus, at the upper opening of the Bladder. It governs separating clear from turbid, excretion but not reception, for conduction. Its treatment point is one cun below the umbilicus, hence named Sanjiao. Its Fu organ is in Qiwei. (Fu here means root; Qiwei is the source of Sanjiao.)
This section is self-explanatory. Danzhong and Yutang acupoints are detailed in the Meridian Acupoints chapter regarding their therapeutic indications.
Difficulty 33 states: The Liver is green and belongs to Wood; the Lung is white and belongs to Metal. Liver sinks in water, but Wood floats in water. Lung floats in water, but Metal sinks in water. What is the meaning? The answer is: The Liver is not pure Wood. It is Yi Jue, the softness of Geng. Speaking broadly, it is Yin and Yang; speaking narrowly, it is husband and wife. It releases its slight Yang and absorbs the slight Yin Qi. Its desire is satisfied, and Metal travels more on the Yin path (Geng Metal resides on the Yin path). Hence, Liver sinks in water. The Lung is not pure Metal. It is Xin Shang, the softness of Bing. Speaking broadly, it is Yin and Yang; speaking narrowly, it is husband and wife. It releases its slight Yin and marries Fire. Its desire is satisfied, and Fire travels more on the Yang path (Bing Fire resides on the Yang path). Hence, Lung floats in water.
This chapter discusses the interdependence of Yin and Yang and the interaction of the Five Elements. The human body is nothing but Yin and Yang; interaction brings life, lack of interaction brings disease, separation brings death. Yuèrén specifically mentions Liver and Lung because Liver governs Blood and Lung governs Qi, making Qi and Blood the masters of Yin and Yang in the body. Once students understand this chapter, they can spiritually comprehend and integrate the principles of all eighty-one difficulties. The principles of the Five Elements are nothing but the interaction of Yin and Yang. For example, the Heavenly Stems Jia, Yi, Bing, Ding, Wu are the Yang path; Ji, Geng, Xin, Ren, Gui are the Yin path. These ten stems are divided into interacting Yin and Yang. Also, Jia-Yi Wood, Bing-Ding Fire, Wu-Ji Earth, Geng-Xin Metal, Ren-Gui Water: the first character of each pair represents Yang or Yin, dividing the Five Elements into interacting Yin and Yang. Also, the Five Tones attach to the Five Elements: Gong-Earth, Shang-Metal, Jue-Wood, Zhi-Fire, Yu-Water. Each varies in size based on the Yin and Yang of the ten stems, attaching the tones to the stems for interacting Yin and Yang. Furthermore, the five Zang organs belong to the Yin path, but their internal structure contains the Yang Five Elements, meaning each Zang-Fu has interacting Yin and Yang. Understanding the meaning of Yin-Yang interaction allows one to fully grasp the principles of this chapter. As the classics say: Liver is not pure Wood; it is Yi Jue, the softness of Geng. This means Liver is the Yin Wood of Yi Jue. Yet it is not pure Wood; Yi combines with Geng, so Geng Metal is contained within it. Geng is Yang and Yi is Yin, so Yi Wood is the softness of Geng Metal. Broadly, it is Yin and Yang; narrowly, it is husband and wife. It also says: "Releases slight Yang and absorbs slight Yin Qi, its desire is satisfied." Release means open, absorb means gather. Yi Wood is the wood of the second month; Yang Qi is not yet prosperous, hence called slight Yang. Geng Metal is the metal of the seventh month; Yin Qi is not yet prosperous