少阳处半表半里，司三焦相火之游行。仲景特揭口苦、咽干、目眩为提纲，是取病机立法矣。夫口、咽、目
三者，脏腑精气之总窍，与天地之气相通者也。不可谓之表，又不可谓之里，是表之入里，里之出表处，正所谓
半表半里也。三者能开能阖，开之可见，阖之不见，恰合为枢之象。苦、干、眩者，皆相火上走空窍而为病，风
寒杂病咸有之，所以为少阳一经总纲也。如曰两耳无闻，胸满而烦，只举得中风一症之半表半里。《内经》之胸
胁痛而耳聋，只举得热症中之半表半里，故提纲不与焉。
少阳之表有二∶脉弦细、头痛、发热，或呕而发热者，少阳伤寒也；耳聋、目赤、胁满而烦，少阳中风也。
此少阳风寒之表，而非少阳之半表。阳明风寒之表，亦有麻、桂症。少阳风寒之表，既不得用麻、桂之汗，亦不
得用瓜蒂、栀豉之吐。若发汗则谵语，吐、下则悸而惊，是少阳之和解，不特在半表而始宜也。少阳初感风寒，
恶寒发热与太阳同，不得为半表。惟寒热不齐，各相回避，一往一来，势若两分，始得谓之半表耳。往来寒热有
三义∶少阳自受寒邪，阳气尚少，不能发热，至五六日郁热内发，始得与寒气相争，而往来寒热，一也；或太阳
伤寒过五六日，阳气已衰，余邪未尽，转属少阳而往来寒热，二也；夫风为阳邪，少阳为风府，一中于风，便往
来寒热，不必五六日而始见，三也。
太阳之身寒在未发热时，如已发热，虽恶寒而身不再寒。阳明之身寒恶寒，只在初得之二日，至三日则恶寒
自罢，便发热而反恶热。惟少阳之寒热有往而复来之异，寒来时便身寒恶寒而不恶热，热来时便身热恶热而不恶
寒，与太阳之如疟，发热恶寒而不恶热，阳明之如虐，潮热恶热而不恶寒者，不侔也。盖以少阳为嫩阳，如日初
出，寒留于半表者不遽散，热出于半里者未即舒，故见此象耳。然寒为欲去之寒，热为新炽之热，寒固为虚寒，
而热亦非实热，故小柴胡汤只治热而不治寒，预补其虚而不攻其实也。小柴胡为半表设，而其症皆属于里，盖表
症既去其半，则病机偏于向里矣。惟寒热往来一症，尚为表邪未去，故独以柴胡一味主之，其他悉属里症药。凡
里症属阳者多实热，
属阴者多虚寒。而少阳为半里，偏于阳，偏于热，虽有虚有实，不尽属于虚也。仲景深以里虚为虑，故于半表未
解时，便用人参以固里。寒热往来，病情见于外；苦、喜、不欲，病情得于内。看苦、喜、欲三字，非真呕、真
满、不能饮食也；看往来二字，即见有不寒热时。寒热往来，胸胁苦满，是无形之表；心烦喜呕，默默不欲饮食，
是无形之里。其或胸中烦而不呕，或渴、或腹中痛，或胁下痞硬，或心悸、小便不利，或咳者，此七症皆偏于里，
惟微热为在表；皆属无形，惟胁下痞硬为有形；皆风寒通症，惟胁下痞硬为少阳。总是气分为病，非有实热可据，
故皆从半表半里之治法。
少阳为游部，其气游行三焦，循两胁，输腠理，是先天真元之气，所以谓之正气。正气虚，不足以固腠理，
邪因腠理之开，得入少阳之部。少阳主胆，为中正之官，正气虽虚，不容邪气内犯，必与之相搏，搏而不胜，所
以邪结胁下也。往来寒热，即邪正相争之象。更实更虚，所以休作有时。邪实正虚，所以默默不欲饮食。仲景于
表症不用人参，此因正邪分争，正不胜邪，故用之扶元气，助正以却邪也。若外有微热而不往来寒热，是风寒之
表未解，不可谓之半表，当小发汗，故去参加桂。心烦与咳，虽逆气有余而正气未虚，不可益气，故去人参。如
太阳汗后身痛，而脉浮沉迟，与下后协热利而心下硬，是太阳之半表里症也。表虽不解，里气已虚，故参桂兼用。
是知仲景用参，皆是预保元气耳。
更有脉症不合柴胡者，仍是柴胡症。本论云∶“伤寒五六日，头汗出，微恶寒，手足冷，心下满，口不欲食，
大便硬，脉细者，此为阳微结，半在里半在表也。脉虽沉紧，不得为少阴病者，阴不得有汗，今头汗出，故可与
小柴胡汤”。此条是少阴阳明并病，而脉症俱是少阴。五六日又少阴发病之期，若谓阴不得有汗，则少阴亡阳，
亦有反汗出者。然阳亡与阴结，其别在大便，亡阳则咽痛吐利，阴结则不能食而大便反硬也。亡阳与阳结，其别
在汗。亡阳者，卫气不固，汗出必遍身；阳结者，热邪郁闭，汗只在头也。阳结、阳微之别在食。阳明阳盛，故
能食而大便硬，此为纯阳结；少阳阳微，故不能食而大便硬，此为阳微结。故欲与柴胡汤，必究其病在半表。然
微恶寒，亦可属少阴，但头汗出，始可属少阳。故反复讲明头汗之义，可与小柴胡而勿疑也。所以然者，少阳为
枢，少阴亦为枢，故见症多相似，必于阴阳表里辨之真而审
之确，始可一剂而瘳。此少阴少阳之疑似症，又柴胡症之变局也。
少阳主人身之半，胁主一身之半，故胁为少阳之枢，而小柴胡为枢机之剂也。岐伯曰∶“中于胁，则入少阳。”
此指少阳自病。然太阳之邪欲转属少阳，少阳之邪欲转并阳明，皆从胁转。如伤寒四五日，身热恶寒，头项强胁
下满者，是太阳少阳并病，将转属少阳之机也。以小柴胡汤与之，所以断太阳之来路。如阳明病，发潮热，大便溏，
小便自可，胸胁满下去者，是少阳阳明并病，此转属阳明之始也。以小柴胡与之，所以开阳明之出路。若据次第
传经之说，必阳明始传少阳，则当大便硬而不当溏，当曰胸胁始满，不当曰满不去矣。又阳明病，胁下硬满，不
大便而呕，舌上白苔者，此虽已属阳明，而少阳之症未罢也。盖少阳之气，游行三焦，因胁下之阻隔，令上焦之
治节不行，水精不能四布，故舌上有白苔而呕。与之小柴胡，转少阳之枢也，则上焦气化始通，津液得下，胃家
不实，而大便自输矣。身 然而自汗解者，是上焦津液所化，故能开发腠理，熏肤、充身、泽毛，若雾露之溉。
与胃中邪热熏蒸而自汗不解者不同。
东垣云∶“少阳有不可汗、吐、下、利小便四禁。”然柴胡症中口不渴，身有微热者，仍加桂枝以取汗。下
后胸胁满微结，小便不利，渴而不呕，头汗出，寒热往来者，用柴胡桂枝干姜汤汗之。下后胸满烦惊，小便不利，
谵语身重者，柴胡龙骨牡蛎汤中用大黄、茯苓以利二便。柴胡症具而反下之，心下满而硬痛者，大陷胸汤下之。医
以丸药下之而不得利，已而微利，胸胁满而呕，日晡潮热者，小柴胡加芒硝下之。是仲景于少阳经中已备汗、下、
利小便法也。若吐法本为阳明初病胸中实不得息、不得食、不得吐而设。少阴病，饮食入口即吐，心下温温欲吐，
复不能吐，亦是胸中实，当吐之。若水饮蓄于胸中，虽是有形而不可为实，故不可吐。何则？少阳之喜呕而发热，
便是中气之虚，但热而不实，故用人参以调中气，上焦得通，津液得下，胃气因和。故少阳之呕与谵语不并见，
所以呕者是少阳本症，谵语是少阳坏症。然本渴而饮水，呕与但欲呕，胸中痛微溏者，又非柴胡症，是呕中又当
深辨也。
按呕、渴虽六经俱有之症，而少阳阳明之病机，在呕、渴中分。渴则属阳明，呕则仍在少阳。如伤寒呕多，
虽有阳明症不可攻之，因三焦之气不通，病未离少阳也。服柴胡汤已，渴者，属阳明也。此两阳
之并合，病已过少阳也。夫少阳始病，便见口苦、咽干、目眩，先以津液告竭矣。故少阳之病，最易转属阳明，
所以发汗即胃实而谵语。故小柴胡中已具或渴之症，方中用参、芩、甘、枣，皆生津液之品，以预防其渴。服之
反渴，是相火炽盛，津液不足以和胃，即转属阳明之机也。
少阳妄下后有二变∶实则心下满而硬痛为结胸，用大陷胸汤下之；虚则但满而不痛为痞，用半夏泻心汤和之。
此二症皆从呕变，因不用柴胡，令上焦不通，津液不下耳。本论云∶“伤寒中风，有柴胡症，但见一症即是，不
必悉具”者，言往来寒热，是柴胡主症。此外兼见胸胁满硬，心烦喜呕，及或为诸症中凡有一者，即是半表半里。
故曰呕而发热者，小柴胡汤主之，因柴胡为枢机之剂也。风寒不全在表，未全入里者，皆可用。故症不必悉具，
而方有加减法也。然柴胡有疑似症，不可不审。如胁下满痛，本渴而饮水呕者，柴胡不中与也。又但欲呕，腹中
痛微溏者，此非柴胡症。如此详明。所云但见一症便是者，又当为细辨矣。
少阳经位于半表半里之间，主管三焦相火的运行。张仲景特别提出口苦、咽干、目眩作为少阳病的提纲，这是根据病机来确立治疗法则的。口、咽、目这三个部位，是脏腑精气的总窍，与天地之气相通。它们不能称为表，也不能称为里，正是从表入里、由里出表的过渡地带，这就是所谓的“半表半里”。这三个器官能开能闭，张开时可见，闭合时不可见，恰好符合“枢”（枢纽）的形象。口苦、咽干、目眩，都是相火上走空窍而导致的疾病，无论是风邪还是寒邪引起的杂病都可能存在，因此作为少阳一经的总纲。如果说两耳听不见、胸中胀满且心烦，这只是举出了中风这一病症中属于半表半里的部分；《内经》中提到的胁痛耳聋，只是举出了热症中的半表半里情况，所以这些不包含在提纲之中。
少阳的表证有两种：脉象弦细、头痛、发热，或者呕吐且发热的，属于少阳伤寒；耳聋、目赤、胁肋胀满且心烦的，属于少阳中风。这是少阳感受风寒的表证，而不是少阳的“半表”概念。阳明病感受风寒的表证，也有使用麻黄汤或桂枝汤的症状表现。对于少阳感受风寒的表证，既不能使用麻黄汤、桂枝汤的发汗法，也不能使用瓜蒂散、栀子豉汤的催吐法。如果误用发汗会导致谵语，误用催吐或泻下会导致心悸和惊骇，这说明少阳病适宜采用和解法，不仅是在半表阶段才适用。少阳初感风寒时，恶寒发热与太阳病相同，不能称之为半表。只有当寒热交替出现，彼此回避，一来一往，势态仿佛分为两部分时，才能称之为半表。往来寒热有三层含义：一是少阳直接感受寒邪，阳气尚少，不能发热，到了五六天郁热内生，才开始与寒气相争，从而出现往来寒热，这是一义；二是太阳伤寒过了五六天，阳气已衰，余邪未尽，转属少阳而出现往来寒热，这是二义；三是风为阳邪，少阳为风之府，一旦中受风邪，便会出现往来寒热，不一定等到五六天才显现，这是三义。
太阳病在身寒而未发热时感到身寒，如果已经发热，虽然仍有恶寒，但身体不再寒冷。阳明病的身寒恶寒，只出现在初得的两天内，到了第三天恶寒自然停止，转而发热并厌恶热。只有少阳病的寒热有往返复来的不同，冷来时便身寒恶寒而不恶热，热来时便身热恶热而不恶寒，这与太阳病的如疟疾般发热恶寒而不恶热，以及阳明病的如潮水般定时发热恶热而不恶寒，是不相同的。因为少阳被称为“嫩阳”，如同太阳初升，停留在半表的寒气不会立刻消散，出于半里的热气也不会立刻舒展，所以出现这种景象。然而，这里的寒是欲去之寒，热是新炽盛的热，寒固然属于虚寒，而热也并非实热，所以小柴胡汤只治疗热而不治疗寒，预先补益其虚而不攻伐其实。小柴胡汤是为半表设立的，但其症状都属于里，既然表证去了一半，则病机偏向于向里发展。只有寒热往来这一症状，尚且表示表邪未去，所以唯独用柴胡一味药为主，其他药物都属于治疗里证的药。凡是里证属于阳的多为实热，属于阴的多为虚寒。而少阳处于半里，偏于阳，偏于热，虽然有虚有实，并不完全属于虚证。张仲景深深担忧里气虚弱，所以在半表未解时，就用人参来固护里气。寒热往来，病情表现在外；口苦、喜呕、不欲饮食，病情体现在内。看“苦”、“喜”、“欲”这三个字，并不是真的剧烈呕吐、真正胀满、完全不能饮食；看“往来”二字，即可以看出有不寒不热的时候。寒热往来、胸胁苦满，是无形的表证；心烦喜呕、默默不欲饮食，是无形的里证。如果出现心中烦闷但不呕吐，或者口渴，或者腹中疼痛，或者胁下痞塞坚硬，或者心悸、小便不利，或者咳嗽的，这七种症状都偏于里，只有微热是在表；都属于无形之邪，只有胁下痞硬是有形之邪；都是风寒的通病，只有胁下痞硬是少阳特有的。总之这些都是气分病变，没有实热可依据，所以都按照半表半里的治法处理。
少阳为游行之部，其气在三焦中游走，循行于两胁，输布于腠理，这是先天的真元之气，所以称之为正气。正气虚弱，不足以固护腠理，邪气便趁着腠理开放，进入少阳的部位。少阳主胆，是中正之官，正气虽然虚弱，不容许邪气内犯，必然与邪气相搏结，搏结而不能胜邪，所以邪气结聚在胁下。往来寒热，就是邪正相争的现象。邪气实而正气虚，所以发作有时。邪实正虚，所以默默不想饮食。张仲景在表证中不用人参，这里是因为正邪分争，正不胜邪，所以用人参扶助元气，帮助正气以驱除邪气。如果体表有微热但没有往来寒热，说明风寒的表证未解，不能称之为半表，应当轻微发汗，所以在方中去掉人参加上桂枝。心烦与咳嗽，虽然是逆气有余而正气未虚，不可益气，所以去掉人参。如果是太阳病发汗后身痛，脉象浮沉迟，或者是泻下后协热利且心下硬，这是太阳病的半表里证。表虽未解，但里气已虚，所以人参和桂枝兼用。由此可知，张仲景使用人参，都是为了预先保护元气。
更有脉症不符合典型柴胡汤证的，仍然是柴胡证。本论说：“伤寒五六日，头汗出，微恶寒，手足冷，心下满，口不欲食，大便硬，脉细的，这叫阳微结，一半在里一半在表。脉虽然沉紧，但不能诊断为少阴病，因为阴证不应该有汗，现在头汗出，所以可以给予小柴胡汤。”这条条文是少阴阳明并病，而脉症俱像是少阴病。五六天又是少阴发病的时期，如果说阴证不能有汗，那么少阴亡阳时，也有反而出汗的情况。然而阳亡与阴结的区别在于大便，亡阳则咽喉痛、吐利，阴结则不能进食而大便反而硬。亡阳与阳结的区别在于汗，亡阳者，卫气不固，出汗必遍全身；阳结者，热邪郁闭，汗只在头部。阳结与阳微的区别在于食欲。阳明阳气盛，所以能进食而大便硬，这是纯阳结；少阳阳气微，所以不能进食而大便硬，这是阳微结。所以要给予柴胡汤，必须究查其病在半表。然而微恶寒，也可以属于少阴，但只有头汗出，才可归属于少阳。所以反复讲明头汗的意义，可以给予小柴胡汤而不要怀疑。之所以这样，是因为少阳为枢，少阴也为枢，所以见到的症状多相似，必须在阴阳表里上辨别得真实且审慎，才可以一剂药而痊愈。这是少阴与少阳的疑似症，也是柴胡证的变局。
少阳主管人身的一半，胁肋主管一身的一半，所以胁肋是少阳的枢纽，而小柴胡汤是调理枢机的方剂。岐伯说：“邪中于胁，则入少阳。”这是指少阳自病。然而太阳的邪气想要转属少阳，少阳的邪气想要转并阳明，都是从胁肋转变。比如伤寒四五日，身热恶寒，头项强直且胁下满的，是太阳少阳并病，即将转属少阳的机转。给予小柴胡汤，是为了阻断太阳邪气传来的路径。如果是阳明病，发潮热，大便溏，小便正常，胸胁满持续不去的，是少阳阳明并病，这是转属阳明的开始。给予小柴胡汤，是为了开启阳明邪气排出的出路。如果依据次第传经的说法，必定是阳明先传少阳，那么应当大便硬而不应当溏，应当说胸胁刚开始满，不应当说满持续不去。又有阳明病，胁下硬满，不大便且呕吐，舌上有白苔的，这虽然已属阳明，但少阳的症状尚未罢休。因为少阳之气游行三焦，因胁下的阻隔，导致上焦的治理调节功能不行，水精不能四布，所以舌上有白苔且呕吐。给予小柴胡汤，转动少阳的枢纽，则上焦气化始通，津液得以下行，胃家不实，而大便自然通畅。身体濈然汗出而自愈的，这是上焦津液所化生，所以能开发腠理，熏蒸皮肤，充实身体，润泽毛发，像雾露灌溉一样。这与胃中邪热熏蒸而自汗不解的情况是不同的。
李东垣说：“少阳有不可汗、吐、下、利小便四禁。”然而在柴胡证中，口不渴，身体有微热的，仍然加桂枝以取汗。泻下后胸胁满微结，小便不利，口渴但不呕吐，头汗出，寒热往来的，用柴胡桂枝干姜汤发汗。泻下后胸满烦惊，小便不利，谵语身重的，在柴胡龙骨牡蛎汤中使用大黄、茯苓以利二便。柴胡证具备却反而被泻下，心下满而硬痛的，用大陷胸汤泻下。医生用丸药泻下而没有得利，随后微利，胸胁满且呕，日晡时分潮热的，用小柴胡汤加芒硝泻下。由此可见，张仲景在少阳经中已经备齐了汗、下、利小便的方法。至于吐法，本是为了阳明初病胸中实邪导致不得呼吸、不得进食、不得呕吐而设。少阴病，饮食入口即吐，心下温温欲吐，但又不能吐出，这也是胸中实邪，应当用吐法。如果是水饮蓄积于胸中，虽然是有形之邪但不能算作实邪，所以不可用吐法。为什么呢？少阳喜欢呕吐且发热，便是中气虚弱，只有热而无实邪，所以用人参来调和中气，上焦得通，津液得下，胃气因而调和。所以少阳的呕吐与谵语不并见，所以呕吐的是少阳本症，谵语是少阳坏症。然而如果原本口渴饮水后呕吐，或者只想呕吐，胸中痛且大便微溏的，又不是柴胡证，所以在呕吐中应当深入辨别。
按：呕吐、口渴虽然是六经都有的症状，但少阳与阳明的病机，在呕吐和口渴中区分。口渴则属阳明，呕吐则仍在少阳。比如伤寒呕吐多，即使有阳明症状也不可攻下，因为三焦之气不通，病未离开少阳。服用柴胡汤后，出现口渴的，属于阳明。这是两阳合并，病已过少阳。夫少阳始病，便见口苦、咽干、目眩，先是以津液告竭。所以少阳的病，最容易转属阳明，所以发汗就会导致胃实而谵语。所以小柴胡汤中已包含可能出现的口渴症状，方中使用人参、黄芩、甘草、大枣，都是生津液的药物，以预防口渴。服用后反而口渴，是相火炽盛，津液不足以和胃，即是转属阳明的机转。
少阳误用下法后有二种变化：实证表现为心下满而硬痛为结胸，用大陷胸汤泻下；虚证表现为但满而不痛为痞，用半夏泻心汤调和。这两种症状都是从呕吐演变而来，因为没用柴胡汤，导致上焦不通，津液不下。本论说：“伤寒中风，有柴胡证，但见一症即是，不必悉具”，意思是往来寒热是柴胡的主症。此外兼见胸胁满硬、心烦喜呕，以及在或然症中凡有一者的，就是半表半里。所以说呕吐且发热的，用小柴胡汤主治，因为柴胡是调理枢机的方剂。风寒不全在表，未全入里的，都可以使用。所以症状不必全部具备，而方剂有加减法。然而柴胡证有疑似症，不可不审察。比如胁下满痛，原本口渴饮水后呕吐的，柴胡汤不适宜使用。又如果只是想要呕吐，腹中痛且大便微溏的，这不是柴胡证。如此详尽明确。所谓“但见一症便是”，又应当仔细辨别。
Shaoyang (Lesser Yang) is located at the half-exterior and half-interior level, governing the circulation of Sanjiao (Triple Burner) Xianghuo (Ministerial Fire). Zhang Zhongjing specifically highlights bitter taste in the mouth, dryness of the throat, and dizziness as the guiding symptoms for Shaoyang disease, thereby establishing treatment principles based on pathogenesis. The mouth, throat, and eyes are the orifices where the essence and Qi of the Zang-Fu organs converge, communicating with the Qi of Heaven and Earth. They cannot be classified as Exterior, nor as Interior; rather, they represent the transition from Exterior to Interior and from Interior to Exterior, which is precisely what is meant by "half-exterior and half-interior." These three orifices can open and close; when open, they are visible; when closed, they are not, perfectly embodying the image of a Pivot (Shu). Bitter taste, dryness, and dizziness are all diseases caused by Ministerial Fire ascending to empty orifices, occurring in various wind-cold mixed diseases, thus serving as the general outline for the Shaoyang channel. If one mentions deafness, chest fullness, and irritability, only half of the half-exterior and half-interior presentation of Wind-Strike is cited. The chest pain and deafness mentioned in the *Neijing* refer only to the half-exterior and half-interior aspect of Heat syndromes; therefore, these are not included in the guiding symptoms.
There are two types of Exterior manifestations in Shaoyang: wiry and fine pulse, headache, fever, or vomiting with fever indicate Shaoyang Cold Damage; deafness, red eyes, hypochondriac fullness, and irritability indicate Shaoyang Wind Strike. These are the Exterior manifestations of Shaoyang affected by Wind-Cold, distinct from the "half-exterior" concept of Shaoyang itself. The Exterior manifestations of Yangming affected by Wind-Cold also present with symptoms treatable by Mahuang Tang (Ephedra Decoction) or Guizhi Tang (Cinnamon Twig Decoction). For Shaoyang affected by Wind-Cold, neither the sweating method of Mahuang Tang/Guizhi Tang nor the vomiting method of Gouti San (Melon Seed Powder) or Zhizi Chishi Tang (Gardenia and Fermented Soybean Decoction) should be used. Inducing sweat leads to delirium; inducing vomiting or purging leads to palpitations and fright. This indicates that the Harmonizing method is suitable for Shaoyang, not only applicable when the pathogen is at the half-exterior stage. When Shaoyang is initially affected by Wind-Cold, aversion to cold and fever are the same as in Taiyang (Greater Yang), so it cannot yet be called half-exterior. Only when chills and fever alternate, avoiding each other, coming and going, appearing as if divided into two parts, can it be termed half-exterior. There are three meanings to alternating chills and fever: First, when Shaoyang directly receives Cold pathogen, Yang Qi is insufficient to generate heat; after five to six days, stagnant Heat emerges internally and contends with Cold, causing alternating chills and fever. Second, after five to six days of Taiyang Cold Damage, Yang Qi has declined, residual pathogens remain, and the condition transfers to Shaoyang, resulting in alternating chills and fever. Third, Wind is a Yang pathogen, and Shaoyang is the residence of Wind; once infected by Wind, alternating chills and fever appear immediately, without waiting for five to six days.
In Taiyang disease, body coldness occurs before fever; once fever appears, although there is aversion to cold, the body no longer feels cold. In Yangming disease, body coldness and aversion to cold occur only in the first two days; by the third day, aversion to cold ceases, followed by fever and aversion to heat. Only in Shaoyang disease do chills and fever alternate and recur. When chills come, there is body coldness and aversion to cold but no aversion to heat; when fever comes, there is body heat and aversion to heat but no aversion to cold. This differs from Taiyang's malaria-like fever and aversion to cold without aversion to heat, and Yangming's tidal fever and aversion to heat without aversion to cold. This is because Shaoyang is referred to as "tender Yang," like the rising sun; Cold lingering at the half-exterior does not dissipate quickly, and Heat emerging from the half-interior does not expand smoothly, hence this presentation. However, the Cold here is Cold about to depart, and the Heat is newly intense; the Cold is indeed Deficient Cold, but the Heat is not Excess Heat. Therefore, Xiaochaihu Tang (Minor Bupleurum Decoction) treats Heat but not Cold, and tonifies Deficiency preemptively rather than attacking Excess. Xiaochaihu Tang is designed for the half-exterior, yet its symptoms belong to the Interior. Since half of the Exterior syndrome has resolved, the pathogenesis shifts toward the Interior. Only the symptom of alternating chills and fever indicates that Exterior pathogens have not fully departed; thus, Chaihu (Bupleuri Radix) alone is used as the principal herb, while other herbs address Interior symptoms. Generally, Interior syndromes belonging to Yang are mostly Excess Heat, while those belonging to Yin are mostly Deficient Cold. Shaoyang, being half-Interior, leans toward Yang and Heat; although it involves both Deficiency and Excess, it is not entirely Deficient. Zhang Zhongjing deeply worries about Interior Deficiency, so he uses Renshen (Ginseng Radix et Rhizoma) to secure the Interior even while the half-exterior is unresolved. Alternating chills and fever manifest externally; bitter taste, desire to vomit, and lack of appetite manifest internally. The characters "bitter," "desire," and "lack of" do not imply severe vomiting, true fullness, or total inability to eat; the character "alternating" implies periods without chills or fever. Alternating chills and fever with hypochondriac bitter fullness constitute an Intangible Exterior; mental irritability, desire to vomit, silence, and lack of appetite constitute an Intangible Interior. If there is mental irritability without vomiting, or thirst, or abdominal pain, or hypochondriac stuffiness and hardness, or palpitations, or difficulty urinating, or coughing, these seven symptoms lean toward the Interior, except for slight fever which is at the Exterior. All are Intangible, except for hypochondriac stuffiness and hardness which is Tangible. All are common to Wind-Cold, except for hypochondriac stuffiness and hardness which is specific to Shaoyang. Ultimately, these are disorders of the Qi level, lacking Excess Heat evidence, so they are treated according to the half-exterior and half-interior method.
Shaoyang is a roaming sector; its Qi circulates through the Sanjiao, follows the hypochondrium, and distributes to the Couli (interstices). This is the primordial Yuan Qi, hence called Zhengqi (Upright Qi). When Zhengqi is deficient, it fails to secure the Couli, allowing pathogens to enter the Shaoyang sector via open interstices. Shaoyang governs the Gallbladder, the official of justice and balance. Although Zhengqi is weak, it does not allow pathogens to invade internally; instead, it contends with them. Unable to overcome the pathogen, the pathogen becomes knotted in the hypochondrium. Alternating chills and fever represent the contention between Pathogen and Upright Qi. Fluctuating Excess and Deficiency cause symptoms to occur at intervals. Pathogen Excess and Upright Deficiency cause silence and lack of appetite. Zhang Zhongjing does not use Renshen in Exterior syndromes generally, but here, because Upright Qi cannot overcome the Pathogen during their contention, Renshen is used to support Yuan Qi and assist Upright Qi in repelling the Pathogen. If there is slight fever on the exterior but no alternating chills and fever, the Wind-Cold Exterior is unresolved and cannot be called half-exterior; mild sweating is required, so Renshen is removed and Guizhi (Cinnamomi Ramulus) is added. Mental irritability and cough indicate excess rebellious Qi but intact Upright Qi; thus, Qi tonification is contraindicated, and Renshen is removed. If Taiyang syndrome presents with body pain after sweating, with a floating, deep, and slow pulse, or with diarrhea accompanied by fever and epigastric hardness after purging, these are Taiyang half-exterior/half-interior syndromes. Although the Exterior is unresolved, the Interior Qi is deficient, so both Renshen and Guizhi are used. Thus, Zhang Zhongjing’s use of Renshen is always to preemptively protect Yuan Qi.
There are cases where pulse and symptoms do not match typical Chaihu presentations, yet they remain Chaihu syndromes. The text states: "Cold damage after five to six days, with head sweating, slight aversion to cold, cold hands and feet, epigastric fullness, lack of desire to eat, hard stool, and a fine pulse, is called Mild Yang Knotting, half in the Interior and half in the Exterior. Although the pulse is deep and tight, it cannot be diagnosed as Shaoyin (Lesser Yin) disease, because Yin syndromes should not have sweating; since there is head sweating, Xiaochaihu Tang may be given." This clause describes concurrent Shaoyin and Yangming disease, with pulse and symptoms resembling Shaoyin. Five to six days is also the period for Shaoyin onset. If one argues Yin syndromes cannot sweat, Shaoyin Yang collapse can also present with spontaneous sweating. However, the distinction between Yang collapse and Yin knotting lies in the stool: Yang collapse presents with sore throat, vomiting, and diarrhea; Yin knotting presents with inability to eat and hard stool. The distinction between Yang collapse and Yang knotting lies in sweating: Yang collapse involves insecure Wei Qi, leading to whole-body sweating; Yang knotting involves trapped Heat, leading to sweating only on the head. The distinction between Yang knotting and Mild Yang Knotting lies in appetite: Yangming Yang excess allows eating with hard stool (Pure Yang Knotting); Shaoyang Yang deficiency prevents eating with hard stool (Mild Yang Knotting). Therefore, to administer Chaihu Tang, one must verify the disease is at the half-exterior. Slight aversion to cold can belong to Shaoyin, but head sweating confirms Shaoyang. Hence, the significance of head sweating is repeatedly explained to justify using Xiaochaihu Tang without doubt. This is because Shaoyang is a Pivot, and Shaoyin is also a Pivot, so symptoms are similar. True and accurate differentiation of Yin/Yang and Exterior/Interior is necessary for a single dose to cure. These are suspected syndromes of Shaoyin and Shaoyang, representing variations of Chaihu syndromes.
Shaoyang governs half of the human body; the hypochondrium governs half of the body. Thus, the hypochondrium is the Pivot of Shaoyang, and Xiaochaihu Tang is the formula for regulating the Pivot. Qibo stated: "If struck in the hypochondrium, the pathogen enters Shaoyang." This refers to primary Shaoyang disease. However, pathogens transferring from Taiyang to Shaoyang, or from Shaoyang to Yangming, all pass through the hypochondrium. For example, after four to five days of cold damage, with body heat, aversion to cold, stiffness of the head and neck, and hypochondriac fullness, this is concurrent Taiyang-Shaoyang disease, indicating the mechanism of transfer to Shaoyang. Administering Xiaochaihu Tang cuts off the incoming path from Taiyang. In Yangming disease, with tidal fever, loose stool, normal urination, and persistent hypochondriac fullness, this is concurrent Shaoyang-Yangming disease, marking the beginning of transfer to Yangming. Administering Xiaochaihu Tang opens the exit route to Yangming. If following the theory of sequential transmission, Yangming should transmit to Shaoyang, implying hard stool rather than loose stool, and initial fullness rather than persistent fullness. In another case of Yangming disease, with hypochondriac hardness, constipation, vomiting, and white tongue coating, although it belongs to Yangming, Shaoyang symptoms have not ceased. Because Shaoyang Qi circulates through the Sanjiao, obstruction in the hypochondrium prevents the governance of the Upper Jiao, stopping the distribution of fluids, resulting in white tongue coating and vomiting. Administering Xiaochaihu Tang rotates the Shaoyang Pivot, allowing Upper Jiao Qi transformation to resume, fluids to descend, Stomach Qi to harmonize, and stool to pass naturally. Spontaneous sweating resolving the disease results from Upper Jiao fluids transforming to open the Couli, steaming the skin, filling the body, and moistening hair, like mist and dew. This differs from spontaneous sweating due to Stomach Heat steaming, which does not resolve the disease.
Li Dongyuan stated: "Shaoyang has four prohibitions: sweating, vomiting, purging, and promoting diuresis." However, in Chaihu syndromes, if the mouth is not thirsty and there is slight body heat, Guizhi is added to induce sweating. After purging, if there is hypochondriac fullness with slight knotting, difficulty urinating, thirst without vomiting, head sweating, and alternating chills and fever, Chaihu Guizhi Ganjiang Tang (Minor Bupleurum, Cinnamon Twig, and Dried Ginger Decoction) is used to induce sweating. After purging, if there is chest fullness, irritability, fright, difficulty urinating, delirium, and heavy body, Dahuang (Rhei Radix et Rhizoma) and Fuling (Poria) are used in Chaihu Longgu Muli Tang (Minor Bupleurum, Dragon Bone, and Oyster Shell Decoction) to promote urination and defecation. If Chaihu symptoms are present but purging is mistakenly applied, resulting in epigastric fullness, hardness, and pain, Dayanxiong Tang (Major Arsenic Decoction) is used to purge. If a physician used pill-based purgatives without relief, followed by slight diarrhea, hypochondriac fullness, vomiting, and tidal fever in the afternoon, Xiaochaihu Tang plus Mangxiao (Natrii Sulfas) is used to purge. Thus, Zhang Zhongjing prepared methods for sweating, purging, and diuresis within the Shaoyang channel. The vomiting method was originally designed for early Yangming disease with solid pathogens in the chest causing breathing and eating difficulties. In Shaoyin disease, vomiting food immediately upon entry, or feeling warm and nauseous in the epigastrium but unable to vomit, indicates solid pathogens in the chest requiring vomiting. However, if water-fluid retention exists in the chest, although tangible, it is not considered solid, so vomiting is contraindicated. Why? Shaoyang’s tendency to vomit with fever indicates Middle Qi deficiency; there is Heat but no Solidity. Thus, Renshen is used to regulate Middle Qi, allowing Upper Jiao to open, fluids to descend, and Stomach Qi to harmonize. Therefore, Shaoyang vomiting and delirium do not occur together; vomiting is the primary Shaoyang symptom, while delirium is a complication. However, if thirst leads to drinking water followed by vomiting, or only nausea, chest pain, and slight diarrhea, this is not a Chaihu syndrome, requiring deep differentiation regarding vomiting.
Note: Vomiting and thirst are symptoms present in all Six Channels, but the pathogenesis of Shaoyang and Yangming is distinguished by them. Thirst indicates Yangming; vomiting indicates Shaoyang. For example, in cold damage with frequent vomiting, even if Yangming symptoms exist, purging is contraindicated because Sanjiao Qi is blocked, and the disease has not left Shaoyang. If thirst develops after taking Chaihu Tang, it indicates Yangming. This represents the combination of two Yang channels, meaning the disease has passed Shaoyang. At the onset of Shaoyang disease, bitter taste, dry throat, and dizziness appear, signaling fluid depletion. Thus, Shaoyang disease easily transfers to Yangming; sweating leads to Stomach Excess and delirium. Xiaochaihu Tang already addresses potential thirst; Renshen, Huangqin (Scutellariae Radix), Gancao (Glycyrrhizae Radix et Rhizoma), and Dazao (Ziziphi Jujubae Fructus) in the formula generate fluids to prevent thirst. If thirst persists after administration, it indicates blazing Ministerial Fire and insufficient fluids to harmonize the Stomach, signaling transfer to Yangming.
After mistaken purging in Shaoyang, two changes occur: Excess manifests as epigastric fullness, hardness, and pain (Jie Xiong / Chest Binding), treated with Dayanxiong Tang; Deficiency manifests as fullness without pain (Pi / Glomus), treated with Banxia Xiexin Tang (Pinellia Decoction to Drain the Epigastrium). Both symptoms evolve from vomiting due to failure to use Chaihu Tang, causing Upper Jiao blockage and failure of fluids to descend. The text states: "In cold damage or wind strike, if Chaihu symptoms are present, seeing one symptom is sufficient; all need not be present." This means alternating chills and fever are the main Chaihu symptom. Additionally, if any of the accompanying symptoms—hypochondriac fullness and hardness, mental irritability, desire to vomit, or any of the conditional symptoms—are present, it constitutes half-exterior and half-interior. Thus, vomiting with fever is treated with Xiaochaihu Tang because Chaihu regulates the Pivot. It can be used when Wind-Cold is neither fully Exterior nor fully Interior. Therefore, symptoms need not be complete, and the formula has modifications. However, Chaihu syndromes have suspected variants that must be carefully examined. For instance, hypochondriac fullness and pain with thirst, drinking water, and vomiting contraindicate Chaihu Tang. Similarly, only nausea, abdominal pain, and slight diarrhea are not Chaihu syndromes. Such detailed clarification means "seeing one symptom is sufficient" requires careful discrimination.