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
能合开之可见。合之不见。恰合为枢之象。苦干眩者。皆相火上走空窍而为病。风寒杂症咸有之。所以为少阳一经总纲
也。如目赤。两耳无闻。胸满而烦。只举中风一症之半表里。内经之胸胁痛而耳聋。只举得热病一症之半表里。故提纲
不与也。
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。目赤胸满而烦者。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。亦有麻黄桂枝症。少阳风寒之表。既不得用麻黄桂枝之汗。亦不得用
瓜蒂栀豉之吐法。发汗则 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。势各两分。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。若风为阳邪。少阳为风藏。一中于风。但往来寒热。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 在初得之一日。至二日则恶寒自罢。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。阳明之如疟。潮热恶热。而不恶寒者不侔也。盖太阳为嫩阳。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。而热为新炽之热。寒固为虚寒。而热亦非实热。故小
柴胡汤治热。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。惟往来寒热一症。尚为表邪未去。故独以柴胡一味主之。其他悉属用里药。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。虽有虚有热。不尽属于虚也。仲景又深以里虚为虑。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。看苦喜不欲等字。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。或胸中痛。或胁下痞硬。或心下悸。小便不利。或咳者。此七症皆偏于里。惟微热微寒为在表。
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。即正邪相争之象。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。强主以逐寇也。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。故去人参加桂。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
沉迟。与下后协热利。而心下硬。是太阳之半表半里症也。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。不得为少阴者。阴不得有汗。今头汗
出。故可与小柴胡汤。此条是少阳阳明并病。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。然亡阳与阴结。其别在大便。亡阳。则咽痛吐利。除阴结则不能食。而大便又反硬也。亡阳。与阴阳结。
其别在汗。亡阳者。卫气不固。汗出必遍身阳结者。热邪闭郁。汗 在头也。阳结阳微结之别。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。
少阳居人身之半。胁居一身之半。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。欲归并阳明。皆从胁转。如伤寒四五日。身热恶风。头项强。胁下满者。
是太阳并病。将转属少阳之机也。以小柴胡与之。所以断太阳之来路。如阳明病发。潮热大便溏。小便自可。胸胁满不
去者。是少阳阳明并病。此转属阳明之路也。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。与小柴胡。转少阳之枢。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。蒸肤泽毛。若雾露之溉。与胃中邪热薰蒸。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。身有微汗者。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。往来寒热者。用柴胡桂枝甘姜汤汗之。下后胸满。烦惊。小便不利。 语。身重者。柴
胡龙骨牡蛎汤中。同大黄茯苓以利小便。柴胡症具。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。是仲景于小阳经中。以备汗下利小便法也。若吐法。本
为阳明初病。胸中实。不得食。不得吐。而设。少阴病。饮食入口即吐。心下兀兀欲吐。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。呕而发热。便见中气之虚。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 语不并见。所以呕者是少阳本症。 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。渴则转属阳明。呕则仍在少阳。如伤寒呕多。虽有阳明症。不可攻之。因三焦之不通。
病未离少阳也。服柴胡汤已。渴者。属阳明也。此两火之并合。病已过少阳也。夫少阳始病。便见口苦。咽干。目眩。
先已津液告竭矣。故太阳之病。最易转属于阳明。所以发汗即胃实而 语。故小柴胡中。已具或渴之症。方中用参苓甘
枣皆生津之品。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。令上下不通。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。小柴胡主之。因柴胡为枢机之剂。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。不渴而饮水呕者。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。它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，是脏腑精气的总汇之窍，与天地之气相通。不能称之为表证，也不能称之为里证，这是表进入里、里透出表的过渡地带，正是所谓的“半表半里”。这三个器官能开也能合，开了就能看见，合了就看不见，恰好符合“枢机”的形象。口苦、咽干、目眩，都是相火上走空窍而导致的病变。风寒等杂症中都有可能出现，所以成为少阳一经的总纲。
如果只出现眼睛红、两耳听不见、胸满且烦躁，这只是举出了中风这一病症在半表半里的表现；《内经》提到的胸胁痛和耳聋，只是举出了热病这一病症在半表半里的表现，所以这些不属于少阳病的提纲。
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、眼睛红、胸满且烦躁的，属于少阳中风。这是少阳感受风寒的表证，而不是少阳的半表证。阳明感受风寒的表证，也有麻黄汤或桂枝汤的症状。对于少阳感受风寒的表证，既不能用麻黄、桂枝的发汗法，也不能用瓜蒂、栀子、豆豉的催吐法。发汗会导致谵语，催吐或泻下会导致心悸和惊悸。因此，少阳病适宜采用和解法，这不仅适用于半表阶段。少阳初感风寒时，恶寒发热与太阳病相同，不能算作半表证；只有当寒热不相齐一，互相回避，一阵冷一阵热，势态各分两半时，才能称为半表证。
“往来寒热”有三层含义：一是少阳自身感受寒邪，阳气尚少，不能发热，到了五六天，郁积的热气从内发出，才开始与寒气相争，从而出现往来寒热，这是第一种情况。二是太阳伤寒过了五六天，阳气已经衰退，余邪未尽，转属到少阳，而出现往来寒热，这是第二种情况。三是风为阳邪，少阳为风脏，一旦中受风邪，直接出现往来寒热，不必等到五六天才显现，这是第三种情况。
太阳病的身寒，出现在未发热之前；如果已经发热，虽然仍有恶寒，但身体不再感到寒冷。阳明病的身寒，恶寒仅出现在刚得病的第一天，到了第二天恶寒自然停止，转而发热并反而怕热。只有少阳病的寒热，有往返复发的不同：发冷时身体就寒冷，恶寒而不恶热；发热时身体就发热，恶热而不恶寒。这与太阳病像疟疾一样，发热恶寒但不恶热，以及阳明病像疟疾一样，潮热恶热但不恶寒的情况是不相同的。
大概太阳经是嫩阳，像初升的太阳，寒邪留在半表没有立即消散，热气出于半里也没有立即舒展，所以出现这种现象。然而，这里的寒是想要离去的寒，热是新近炽盛的熱，寒固然是虚寒，热也不是实热。所以小柴胡汤主要治疗热，而不专门治疗寒，预先补益其虚损而不攻伐其实邪。小柴胡汤是为半表证设立的，但其症状多归属于里。因为表证去了一半，病机偏向于向里发展。只有“往来寒热”这一症状，说明表邪尚未完全去除，所以单独用柴胡一味药为主药，其他药物都属于治里的药。凡是里证属于阳的，多是实热；属于阴的，多是虚寒。而少阳处于半里，偏于阳，偏于热，虽然有虚有热，并不完全属于虚证。张仲景又深深担忧里气虚弱，所以在半表证未解时，就加入人参以巩固里气。
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“口苦、喜呕、不欲饮食”这几个字，并不是真的剧烈呕吐和胀满，而是指不能正常饮食。看“往来”二字，即见到有不寒不热的时候。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。或者胸中烦闷但不呕吐，或者口渴，或者胸中痛，或者胁下痞塞坚硬，或者心下悸动，小便不利，或者咳嗽的，这七种症状都偏于里。只有微热微寒是在表，也都属于无形。只有胁下痞塞坚硬是有形的。这些都是风寒的通病，只有胁下痞硬是少阳病的总特征，这是气分受了病，并没有实热可依据，所以都按照半表半里的治法来处理。
少阳经是游行之部，其气在三焦中游行，沿着两胁，输布于腠理，这就是先天的真元之气，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的机会，侵入少阳的部位。少阳主胆，是中正之官，正气虽然虚弱，也不容许邪气内犯，必定会与邪气相搏结。搏结而不能战胜邪气，所以邪气结聚在胁下。往来寒热，就是正气与邪气相争的现象，虚实交替，所以发作和休止都有定时。邪气实而正气虚，所以默默不想吃东西。张仲景在治疗表证时不用人参，这里是因为正邪分争，正气不胜邪气，所以用人参扶助元气，强壮主体以驱逐寇贼。如果外表有微热，而没有往来寒热，说明风寒的表证未解，不能称为半表证，应当轻微发汗，所以去掉人参加上桂枝。心烦与咳嗽，虽然是逆气有余，但正气未虚，不可补气，所以去掉人参。如果是太阳病发汗后，身体疼痛且脉象沉迟，或者是泻下后协热利且心下硬，这是太阳病的半表半里证。表证虽未解，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。
更有脉症不符合小柴胡汤证的，仍然是小柴胡汤证。本论说：伤寒五六天，头出汗，微恶寒，手足冷，心下满，口不想吃东西，大便硬，脉细的，这叫“阳微结”，一半在里，一半在表。脉象虽然沉紧，但不能诊断为少阴病，因为阴证不应该有汗，现在头出汗，所以可以给予小柴胡汤。这一条是少阳阳明并病，而脉症都像少阴病，五六天又是少阴病发病的时期。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。然而亡阳与阴结的区别在于大便：亡阳会有咽痛、吐利；阴结则不能进食，而且大便反而变硬。亡阳与阳结的区别在于汗：亡阳的人，卫气不固，出汗必遍全身；阳结的人，热邪闭郁，汗出仅在头部。阳结与阳微结的区别在于食欲：阳明阳气盛，所以能进食，大便硬，这是纯阳结；少阳阳气微弱，所以不能进食而大便硬，这是阳微结。所以想用柴胡汤，必须究明病在半表。然而微恶寒也可以属于少阴，只有头出汗，才可以属于少阳。所以反复讲明头出汗的意义，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，所以出现的症状多相似。必须在阴阳表里上辨别得真切，审察得确切，才能一剂药而痊愈。这是少阳与少阳疑似症的鉴别，也是柴胡汤证的变局。
少阳居于人身的一半，胁肋居于一身的一半，所以胁肋是少阳的枢纽，而小柴胡汤是枢机之剂。岐伯说：邪气中于胁肋，则进入少阳。这是指少阳自病。然而太阳的邪气，欲转属少阳；少阳的邪气，欲归并阳明，都是从胁肋转变。如伤寒四五天，身热恶风，头项强，胁下满的，是太阳并病，即将转属少阳的机转。给予小柴胡汤，是为了阻断太阳邪气来的路径。如阳明病发作，潮热，大便溏，小便正常，胸胁满不去的，是少阳阳明并病，这是转属阳明的路径。给予小柴胡汤，是为了开启阳明邪气去的路径。如果依据次第传经的说法，一定是阳明才传少阳，那么应该大便硬而不应该溏，应该说胸胁刚开始满，而不应该说满不去。又有阳明病，胁下硬满，不大便而呕，舌上有白苔的，这虽然已经属于阳明，但少阳的症状未罢。大概少阳之气，游行三焦，因胁下的阻隔，导致上焦的治节不行，水精不能四布，所以舌上有白苔，并且呕吐。给予小柴胡汤，转动少阳的枢纽，则上焦气化始通，津液得以向下输送，胃家不实，大便自然通畅。身体濈然自汗而解的，这是由上焦津液化生而来，所以能开发腠理，蒸润皮肤毫毛，像雾露灌溉一样，这与胃中邪热薰蒸而自汗不解的情况是不同的。
李东垣说：少阳病有不可汗、不可吐、不可下、不可利小便四种禁忌。然而在柴胡汤证中，口不渴，身体有微汗的，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，头出汗，往来寒热的，用柴胡桂枝干姜汤发汗。泻下后胸满，烦惊，小便不利，谵语，身体重的，在柴胡加龙骨牡蛎汤中，配合大黄、茯苓以利小便。柴胡汤证具备，反而被误下，心下满而硬痛的，用大陷胸汤泻下。医生用丸药泻下，而不得利，随后微利，胸胁满而呕，日晡潮热的，用小柴胡汤加芒硝泻下。由此可见，张仲景在少阳经中，备有了汗、下、利小便的方法。至于吐法，本来是为阳明初病，胸中实，不能进食，不能吐出而设的。少阴病，饮食入口即吐，心下兀兀欲吐，但又不能吐出，也是胸中实，应当用吐法。如果水饮蓄积于胸中，虽然是有形之物，但不能算作实邪，所以不可用吐法。为什么呢？少阳病喜欢呕吐，呕吐且发热，便显示出中气之虚，只有热而没有实邪，所以用人参来调和中气。上焦得通，津液得下，胃气因而调和，所以少阳病的呕吐，不与谵语同时出现。所以呕吐是少阳的本症，谵语是少阳的坏症。然而原本口渴而饮水后呕吐，或者只想呕吐，胸中痛，大便微溏的，又不是柴胡汤证，所以在呕吐中应当深入辨别。按呕吐和口渴虽然是六经都有的症状，但少阳和阳明的病机，在呕吐和口渴中可以区分。口渴则转属阳明，呕吐则仍在少阳。如伤寒呕吐多，即使有阳明症状，也不可攻下，因为三焦不通，病未离开少阳。服用柴胡汤后，出现口渴的，属于阳明。这是两火合并，病已过少阳了。夫少阳始病，便见口苦、咽干、目眩，先已津液告竭。所以太阳的病，最容易转属于阳明。所以发汗后即胃实而谵语。故小柴胡汤中，已具备可能口渴的症状，方中用人参、茯苓、甘草、大枣都是生津之品，以预防其口渴。服药后反而口渴，是相火炽盛，津液不足以和胃，即转属阳明的机转。
少阳病误下后，有两种变化：实证则是心下满而硬痛，为结胸，用大陷胸汤泻下；虚证则是但满而不痛，为痞证，用半夏泻心汤调和。这两种症状都从呕吐演变而来，因为没用柴胡汤，导致上下不通，津液不下。
本论说：伤寒中风，有柴胡症，但见一症即是，不必悉具。意思是往来寒热是柴胡汤的主症，此外兼见胸胁满硬、心烦喜呕，以及在或然症中凡有一个症状，就是半表半里证。所以说“呕而发热者”，小柴胡汤主之。因为柴胡是枢机之剂，风寒不全在表，也未全入里的，都可以使用。所以症状不必全部具备，而方剂有加减法。然而柴胡汤有疑似症，不可不审慎。如胁下满痛，不渴而饮水呕吐的，柴胡汤不可用。又如只想呕吐，腹中痛，大便微溏的，这不是柴胡汤证。如此详明，所谓“但见一症便是”的说法，又应当仔细辨别了。
Shaoyang (Lesser Yang) is located at the half-exterior and half-interior level. It governs the circulation of Sanjiao (Triple Burner) Xianghuo (Ministerial Fire). Zhang Zhongjing specifically highlights "bitter taste in the mouth, dry throat, and dizziness" as the guiding symptoms for Shaoyang disease, which establishes treatment principles based on pathogenesis. The mouth, pharynx, 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 syndromes, nor can they be classified as Interior syndromes; rather, they represent the transition zone where Exterior pathogens enter the Interior and Interior pathogens emerge to the Exterior, precisely what is termed "half-exterior and half-interior." These three orifices can open and close; when open, they are visible; when closed, they are invisible, perfectly embodying the image of the Pivot (Shu). Bitter taste, dry throat, and dizziness are all diseases caused by Ministerial Fire ascending to these empty orifices. Such manifestations occur in wind-cold and miscellaneous diseases, thus serving as the general outline for the Shaoyang channel.
If only red eyes, deafness in both ears, chest fullness, and irritability are present, this merely illustrates the half-exterior and half-interior aspect of one symptom of Wind-Strike (Zhongfeng). The chest and hypochondriac pain with deafness mentioned in the *Neijing* (*Huangdi Neijing*) only illustrates the half-exterior and half-interior aspect of one symptom of Heat Disease. Therefore, these do not constitute the guiding symptoms.
There are two types of Exterior syndromes in Shaoyang: a wiry and fine pulse, headache, fever, or vomiting with fever indicates Shaoyang Cold Damage (Shanghan); deafness, red eyes, chest fullness, and irritability indicate Shaoyang Wind Strike (Zhongfeng). These are the Exterior syndromes of Shaoyang affected by wind-cold, not the half-exterior of Shaoyang itself. The Exterior syndromes of Yangming affected by wind-cold also present with symptoms treatable by Mahuang Decoction (Ephedra Decoction) or Guizhi Decoction (Cinnamon Twig Decoction). For Shaoyang Exterior syndromes caused by wind-cold, neither diaphoresis with Mahuang or Guizhi nor emesis with Gouti (Melon Seed), Zhizi (Gardenia Fruit), or Chidouchi (Fried Soybean) should be used. Diaphoresis leads to delirious speech (Chanyu); emesis or purgation leads to palpitations and fright. Therefore, harmonization (Hexie) is suitable for Shaoyang, not only 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) and cannot be considered half-exterior. Only when chills and fever are uneven, avoiding each other, alternating back and forth, and dividing into two distinct states, can it be called half-exterior.
"Wandering chills and fever" (Wanglai Hanre) has three meanings: First, when Shaoyang itself is affected by cold pathogens, Yang Qi is insufficient to generate fever. By the fifth or sixth day, pent-up heat erupts from within and begins to contend with the cold, resulting in wandering chills and fever (Case 1). Second, after five or six days of Taiyang Cold Damage, Yang Qi has declined, residual pathogens remain, and the condition transfers to Shaoyang, presenting with wandering chills and fever (Case 2). Third, wind is a Yang pathogen, and Shaoyang is the organ associated with wind. Upon contracting wind, wandering chills and fever appear immediately, without waiting for five or six days (Case 3).
The body chill in Taiyang occurs before fever develops. Once fever appears, although there is aversion to cold, the body no longer feels cold. In Yangming, body chill and aversion to cold occur only on the first day of illness; by the second day, aversion to cold ceases, fever arises, and there is aversion to heat. Only in Shaoyang is there a unique pattern of recurring chills and fever: when chills come, the body is cold, with aversion to cold but not heat; when fever comes, the body is hot, with aversion to heat but not cold. This differs from Taiyang malaria-like patterns (fever and aversion to cold, no aversion to heat) and Yangming tidal fever patterns (tidal fever and aversion to heat, no aversion to cold).
Taiyang represents "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 readily, hence this presentation. However, the cold here is cold that is departing, 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 the heat but not the cold, preemptively tonifying deficiency rather than attacking excess. Xiaochaihu Tang is designed for the half-exterior, yet its symptoms belong largely to the Interior. Since half of the Exterior syndrome has resolved, the pathogenesis shifts toward the Interior. Only the symptom of wandering chills and fever indicates that exterior pathogens have not fully departed; thus, Chaihu (Bupleuri Radix) is used alone as the principal herb, while other herbs address the Interior. 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 there is deficiency and heat, it is not entirely deficient. Zhang Zhongjing deeply worried about Interior deficiency, so even when the half-exterior was unresolved, he added Renshen (Ginseng Radix et Rhizoma) to secure the Interior.
Wandering chills and fever manifest the pathology externally; bitter taste, preference for vomiting, and lack of desire for food manifest the pathology internally. The phrases "bitter taste, preference for vomiting, lack of desire for food" do not imply severe vomiting or distension, but rather an inability to eat normally. The term "wandering" implies intervals without chills or fever. Wandering chills and fever, along with hypochondriac distress and fullness, represent formless Exterior syndromes; mental irritability, preference for vomiting, and silent lack of desire for food represent formless Interior syndromes. Alternatively, if there is mental oppression without vomiting, thirst, chest pain, hypochondriac stiffness and fullness, epigastric palpitations, dysuria, or cough, these seven symptoms lean toward the Interior. Only slight fever and slight chills indicate involvement of the Exterior, and these are also formless. Only hypochondriac stiffness and fullness is tangible. These are common patterns of wind-cold, but hypochondriac stiffness and fullness is the hallmark of Shaoyang. This is a disorder of the Qi division, lacking evidence of excess heat; therefore, treatment follows the half-exterior and half-interior method.
Shaoyang is a traveling department; its Qi circulates through the Sanjiao, follows the hypochondrium, and distributes to the interstices (Couli). This is the primordial Yuan Qi of congenital origin, hence called "Righteous Qi" (Zhengqi). When Righteous Qi is deficient, it fails to consolidate the Couli, allowing pathogens to enter the Shaoyang region via open pores. Shaoyang governs the Gallbladder, the official of justice and balance. Although Righteous Qi is weak, it does not tolerate pathogenic invasion and must contend with it. If it cannot overcome the pathogens, they become knotted in the hypochondrium. Wandering chills and fever represent the struggle between Righteous Qi and pathogens; alternations of excess and deficiency cause periodic onset and remission. Pathogen excess and Righteous Qi deficiency lead to silence and lack of appetite. Zhang Zhongjing does not use Renshen for Exterior syndromes generally, but here uses it because Righteous Qi cannot overcome pathogens, thus supporting Yuan Qi and strengthening the host to expel invaders. If there is slight external heat without wandering chills and fever, the wind-cold Exterior is unresolved and not yet half-exterior; mild diaphoresis is indicated, so Renshen is removed and Guizhi (Cinnamomi Ramulus) is added. Mental irritability and cough indicate rebellious Qi excess but intact Righteous Qi; thus, tonification is contraindicated, and Renshen is removed.
If after Taiyang diaphoresis, body pain and a deep, slow pulse occur, or after purgation,協熱利 (diarrhea with heat) and epigastric hardness occur, 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 Xiaochaihu Tang, yet it remains a Xiaochaihu indication. The text states: After five or six days of Cold Damage, sweating on the head, slight aversion to cold, cold hands and feet, epigastric fullness, lack of desire for food, hard stool, and a fine pulse indicate "Yang Minor Knotting" (Yang Wei Jie), half in the Interior and half in the Exterior. Although the pulse is deep and tight, it cannot be Shaoyin (Lesser Yin) because Yin syndromes should not sweat. Since the head sweats, Xiaochaihu Tang may be given. This clause describes concurrent Shaoyang-Yangming disease, with pulse and symptoms resembling Shaoyin. Five or six days is also the period for Shaoyin disease onset. If Yin syndromes cannot sweat, Shaoyin collapse of Yang may also present with sweating. However, the distinction between collapse of Yang and Yin knotting lies in the stool: collapse of Yang presents with sore throat, vomiting, and diarrhea; Yin knotting presents with inability to eat and hard stool. The distinction between collapse of Yang and Yang knotting lies in sweating: collapse of Yang involves insecure Defensive Qi, causing whole-body sweating; Yang knotting involves heat closure, causing sweating only on the head. The distinction between Yang knotting and Yang minor knotting lies in appetite: Yangming Yang excess allows eating with hard stool (pure Yang knotting); Shaoyang Yang deficiency prevents eating with hard stool (Yang minor knotting). Thus, to use Chaihu Tang, one must verify the disease is half-exterior. Slight aversion to cold may belong to Shaoyin, but head sweating confirms Shaoyang. Hence, the significance of head sweating is repeatedly explained to justify Xiaochaihu Tang without doubt. This is because both Shaoyang and Shaoyin serve as Pivots, leading to similar symptoms. True differentiation of Yin/Yang and Exterior/Interior is required for a single dose to cure. These are differential diagnoses between Shaoyin and Shaoyang, representing variations of Chaihu indications.
Shaoyang resides at the midpoint of the body; the hypochondrium is the midpoint of the torso. Thus, the hypochondrium is the pivot of Shaoyang, and Xiaochaihu Tang is the pivot-regulating formula. Qibo stated: "Pathogens striking the hypochondrium enter Shaoyang," referring to primary Shaoyang disease. However, Taiyang pathogens transferring to Shaoyang, and Shaoyang pathogens merging into Yangming, both transition via the hypochondrium. For example, after four or five days of Cold Damage, with body heat, aversion to wind, stiff neck and occiput, and hypochondriac fullness, this is Taiyang concurrent disease transitioning to Shaoyang. Giving Xiaochaihu Tang blocks the incoming path of Taiyang. In Yangming disease with tidal fever, loose stool, normal urination, and persistent hypochondriac fullness, this is Shaoyang-Yangming concurrent disease, indicating the path to Yangming. Giving Xiaochaihu Tang opens the exit route to Yangming. If following the theory of sequential transmission, Yangming should transmit to Shaoyang only after stool becomes hard and hypochondriac fullness just begins. But here, stool is loose and fullness persists. Another case: Yangming disease with hypochondriac stiffness/fullness, constipation, vomiting, and white tongue coating. Although belonging to Yangming, Shaoyang symptoms persist. Shaoyang Qi circulates the Sanjiao; obstruction in the hypochondrium prevents Upper Jiao regulation, stopping the distribution of fluids, causing white tongue coating and vomiting. Xiaochaihu Tang rotates the Shaoyang pivot, restoring Upper Jiao Qi transformation, allowing fluids to descend, preventing stomach excess, and enabling natural bowel movement. Profuse spontaneous sweating resolving the disease results from Upper Jiao fluids transforming to open Couli, moistening skin and hair like mist and dew, differing from sweating due to Stomach heat steaming.
Li Dongyuan stated: Shaoyang has four prohibitions: no diaphoresis, no emesis, no purgation, no diuresis. However, in Chaihu syndromes with no thirst and slight sweating, Guizhi is added to induce sweating. After purgation, with hypochondriac fullness, slight knotting, dysuria, thirst without vomiting, head sweating, and wandering chills/fever, Chaihu Guizhi Ganjiang Tang (Minor Bupleurum, Cinnamon Twig, and Dried Ginger Decoction) is used for diaphoresis. After purgation, with chest fullness, irritability/fright, dysuria, delirium, and heaviness, Dahuang (Rhei Radix et Rhizoma) and Fuling (Poria) are added to Chaihu Longgu Muli Tang (Minor Bupleurum with Dragon Bone and Oyster Shell Decoction) for diuresis. If Chaihu symptoms exist but purgation is mistakenly applied, causing epigastric fullness, hardness, and pain, Dayanxiong Tang (Major Thorax-Penetrating Decoction) is used for purgation. If pills were used for purgation causing no relief, followed by slight purgation, hypochondriac fullness, vomiting, and afternoon tidal fever, Xiaochaihu Tang plus Mangxiao (Natrii Sulfas) is used for purgation. Thus, Zhang Zhongjing provided methods for diaphoresis, purgation, and diuresis within the Shaoyang chapter. Emesis is originally indicated for early Yangming disease with real excess in the chest, inability to eat or vomit. Shaoyin disease with immediate vomiting upon swallowing, epigastric restlessness, and inability to vomit also indicates chest excess requiring emesis. However, water-fluid retention in the chest, though tangible, is not "real excess" and should not be treated with emesis. Why? Shaoyang's tendency to vomit, combined with fever, reveals Middle Qi deficiency with heat but no excess; thus, Renshen is used to harmonize Middle Qi. Once the Upper Jiao is unblocked, fluids descend, and Stomach Qi harmonizes, Shaoyang vomiting does not co-occur with delirium. Vomiting is the primary Shaoyang symptom; delirium is a deteriorated symptom. However, thirst with vomiting after drinking, or mere desire to vomit with chest pain and loose stool, are not Chaihu syndromes, requiring deep differentiation of vomiting. Although vomiting and thirst occur in all six channels, the pathogenesis of Shaoyang vs. Yangming is distinguished by them: thirst indicates transfer to Yangming; vomiting indicates retention in Shaoyang. For example, in Cold Damage with frequent vomiting, even with Yangming symptoms, purgation is contraindicated because Sanjiao blockage means the disease has not left Shaoyang. Thirst developing after taking Chaihu Tang indicates Yangming involvement, signifying the merger of two Fires and departure from Shaoyang.
At the onset of Shaoyang disease, bitter taste, dry throat, and dizziness appear, indicating prior depletion of fluids. Thus, Taiyang disease easily transfers to Yangming; diaphoresis leads to Stomach excess and delirium. Xiaochaihu Tang already anticipates potential thirst; Renshen, Fuling, Gancao (Licorice Root), and Dazao (Jujube Fruit) are fluid-generating ingredients to prevent thirst. If thirst develops after administration, it indicates blazing Ministerial Fire and insufficient fluids to harmonize the Stomach, signaling transfer to Yangming.
After mistaken purgation in Shaoyang, two changes occur: Excess manifests as epigastric fullness, hardness, and pain (Jie Xiong / Chest Binding), treated with Dayanxiong Tang for purgation. Deficiency manifests as fullness without pain (Pi / Glomus), treated with Banxia Xiexin Tang (Pinellia Heart-Draining Decoction) for harmonization. Both stem from vomiting due to failure to use Chaihu, causing blockage of upper/lower flow and failure of fluids to descend.
The text states: In Cold Damage or Wind Strike, if Chaihu symptoms are present, seeing even one symptom is sufficient; all need not be present. Wandering chills and fever are the main Chaihu symptom. If accompanied by hypochondriac fullness/hardness, mental irritability/preference for vomiting, or any of the optional symptoms, it constitutes a half-exterior/half-interior syndrome. Thus, "vomiting with fever" is treated with Xiaochaihu Tang. As Chaihu is a pivot-regulating agent, it applies to wind-cold that is neither fully Exterior nor fully Interior. Hence, symptoms need not be complete, and the formula has modifications. However, differential diagnosis is crucial. Hypochondriac fullness/pain with no thirst but vomiting after drinking contraindicates Chaihu. Mere desire to vomit with abdominal pain and loose stool is not a Chaihu syndrome. Such detailed clarification requires careful differentiation of "seeing one symptom is sufficient."