凡看伤寒，以传经直中四字为纲领。传经者，由太阳传阳明，由阳明传少阳，由少阳传
太阴，由太阴传少阴，由少阴传厥阴。此名循经传也。亦有越经传者，如寒邪初客太阳，有
不传阳明而径传少阳者，有不传阳明经而径入阳明腑者。亦有由阳明不传少阳而径入本腑者
亦有少阳不传三阴而径入胃腑者，亦有传一、二经而止者，亦有始终只在一经者。虽所传
各各不同，其为传经则一也。若夫直中者，谓不由阳经传入而径中三阴者也。中太阴，则病
浅。中少阴，则病深。中厥阴，则愈深矣。此其所当急温也。夫传经之邪，在表为寒，入里
即为热证，不比直中之邪，则但寒而无热也。先明传经直中，庶寒、热之剂，不至混投矣。
仲景三阴条下，混同立言，而昧者不察，无怪其意乱心迷也乎？
伤寒主治四字者，表、里、寒、热也。太阳、阳明为表，太阴、少阴、厥阴为里，少阳
居表里之间，谓之半表半里。凡伤寒自阳经传入者，为热邪。不由阳经传入，而直入阴经者
谓之中寒，则为寒邪。此皆前人要旨也，而予更即表、里、寒、热四字，举八言以晰之，任
伤寒千变万化，总不出此。夫伤寒症，有表寒，有里寒，有表热，有里热，有表里皆热，有
表里皆寒，有表寒里热，有表热里寒。何谓表寒？伤寒初客太阳，头痛发热而恶寒者，名曰
外感，经所谓体若燔炭，汗出而散者是也。阳明解肌，少阳和解，其理一也。何谓里寒
凡伤寒不由阳经传入，而直入阴经，手足厥冷，脉微细，下利清谷者，名曰中寒，仲景所
谓急温之，宜四逆汤者是也。何谓表热？凡人冬不藏精，微寒袭于肌肉之间，酝酿成热，至
春感温气而发者曰温病，至夏感热气而发者曰热病。其症头痛发热，与正伤寒同，但不恶寒
而口渴，与正伤寒异耳。《伤寒赋》云∶温热发于春夏，务须柴葛以解肌。言病邪在表，故
用柴葛，肌肉韫热，故用黄芩、知母以佐之，此活法也。何谓里热？凡伤寒渐次传里，与夫
春温夏热之症，热邪入里，皆为里热。其在太阴，则津液少，少阴则咽干口燥，厥阴则消渴
仲景所谓急下之，而用大柴胡、三承气者是也。何谓表里皆热？如伤寒阳明证，传于本腑
外而肌肉，内而胃腑，热气熏蒸，口渴谵语，此散漫之热，邪未结聚，治用白虎汤，外透
肌肤，内清腑脏，俾表里两解，不比邪热结实，专在肠胃可下而愈也。正伤寒有此，而温热
之病，更多有此，不可不察。何谓表里皆寒？凡伤寒表受寒邪，更兼直中于里，此为两感寒
证。仲景用麻黄附子细辛汤是也。何谓表寒里热？如两感热证，一日太阳与少阴同病，二日
阳明与太阴同病，三日少阳与厥阴同病。三阳为寒，三阴已成热证，岂非表寒而里热乎？亦
有火郁在内，而加以外感，亦为表寒里热之候。更有火亢已极，反兼水化，内热闭结而外有
恶寒之状者，其表似寒而里实热，误投热剂，下咽即败矣。何谓表热里寒？如人本体虚寒，
而外感温热之邪，此为标热本寒，清剂不宜太过。更有阴寒在下，逼其无根失守之火，发扬
于上，肌肤大热，欲坐卧泥水之中，其表似热，其里实寒，误投寒剂，入胃即危矣。伤寒变
证，万有不齐，而总不外乎表、里、寒、热四字。其表里寒热，变化莫测，而总不出此八言
以为纲领。予寝食于兹者，三十年矣。得之于心，应之于手，今特指出而发明之，学人其可
不尽心乎！
凡诊治伤寒，以“传经”和“直中”四个字为纲领。所谓传经，是指病邪由太阳经传入阳明经，由阳明经传入少阳经，由少阳经传入太阴经，由太阴经传入少阴经，由少阴经传入厥阴经。这称为循经传（按六经顺序依次相传）。也有越经传（跳过中间经络直接传入）的情况，例如寒邪初犯太阳经，有不传入阳明经而直接传入少阳经的，有不传入阳明经之经表而直接侵入阳明腑的。也有从阳明经不传入少阳经而直接侵入本腑的；也有从少阳经不传入三阴经而直接侵入胃腑的；也有只传一、二经就停止的；也有始终只在一经受病的。虽然所传途径各不相同，但都属于传经这一类。至于直中，是指病邪不由阳经传入，而是直接中伤三阴经。中伤太阴经，则病情较轻浅；中伤少阴经，则病情较深重；中伤厥阴经，则病情更深重了。这是应当紧急温补的情况。凡是传经而来的邪气，在体表表现为寒证，入里后即为热证，不像直中的邪气，只有寒证而没有热证。先弄明白传经和直中的区别，那么寒凉和温热的药剂，就不会混淆误用了。张仲景在三阴篇条文中，论述较为混同，那些不明事理的人不加考察，难怪会心意混乱、迷惑不解呢？
伤寒主治的关键在于“表、里、寒、热”四个字。太阳经、阳明经属于表，太阴经、少阴经、厥阴经属于里，少阳经居于表里之间，称为半表半里。凡是伤寒从阳经传入的，属于热邪。不由阳经传入，而直接侵入阴经的，称为中寒，属于寒邪。这些都是前人的精要之处，而我进一步依据表、里、寒、热四字，提出八种情况来阐明它，任凭伤寒如何千变万化，总不出这八种情况。伤寒病症，有表寒，有里寒，有表热，有里热，有表里皆热，有表里皆寒，有表寒里热，有表热里寒。什么是表寒？伤寒初起客于太阳经，出现头痛、发热且恶寒的症状，称为外感，即《内经》所说的身体像燃烧的炭火一样热，出汗后热散而愈的情况。阳明经用解肌法，少阳经用和解法，道理是一样的。什么是里寒？凡是伤寒不由阳经传入，而直接侵入阴经，出现手足厥冷、脉象微细、下利清谷（大便中有未消化的食物）的症状，称为中寒，张仲景所说的应当紧急温补，适宜使用四逆汤的情况。什么是表热？大凡人冬天不能藏精，微寒侵袭肌肉之间，酝酿成热，到春天感受温气而发病的称为温病，到夏天感受热气而发病的称为热病。其症状是头痛发热，与正伤寒相同，只是不恶寒而口渴，这与正伤寒不同。《伤寒赋》说：温热病发于春夏季节，务必用柴胡、葛根来解肌。意思是病邪在表，所以用柴胡、葛根，肌肉蕴藏着热，所以用黄芩、知母来辅助治疗，这是灵活的方法。什么是里热？凡是伤寒逐渐传入里部，以及春天温病、夏天热病的病症，热邪入里，都属于里热。如果在太阴经，则津液减少；在少阴经，则咽干口燥；在厥阴经，则消渴（极度口渴多饮）。张仲景所说的应当紧急攻下，而使用大柴胡汤、三种承气汤的情况。什么是表里皆热？如伤寒阳明证，传入本腑，外在肌肉，内在胃腑，热气熏蒸，口渴谵语（神志不清说胡话），这是散漫的热邪，邪气尚未结聚，治疗用白虎汤，向外透达肌肤，向内清脏腑，使表里两解，不像邪热结实，专门在肠胃可以通过泻下治愈的情况。正伤寒有此症，而温热病更多有此症，不可不仔细辨别。什么是表里皆寒？凡是伤寒体表受寒邪，又兼有寒邪直中于里，这称为两感寒证（表里同时受寒）。张仲景使用麻黄附子细辛汤的情况。什么是表寒里热？如两感热证，第一天太阳经与少阴经同病，第二天阳明经与太阴经同病，第三天少阳经与厥阴经同病。三阳经表现为寒，三阴经已成热证，难道不是表寒而里热吗？也有火郁结在内，又加上外感，也表现为表寒里热的证候。更有火亢盛到了极点，反而兼有水化的表现，内热闭结而外表有恶寒的样子，其表面看似寒证而内部实为热证，误投温热药剂，咽下就会败坏病情。什么是表热里寒？如人体本身体质虚寒，又外感温热之邪，这称为标热本寒，清热药剂不宜太过。更有阴寒在下，逼迫无根失守之火，发扬于上，肌肤大热，想要坐卧在泥水中，其表面看似热证，内部实为寒证，误投寒凉药剂，进入胃部就会危及生命。伤寒变证，万有不齐，但总不外乎表、里、寒、热四个字。其表里寒热的变化莫测，但总不出这八个字作为纲领。我在此钻研三十年了。心得于心，应用在手，现在特别指出并阐明它，学习的人岂可不尽心研究呢！
In the diagnosis and treatment of Shanghan (Cold Damage), the four key concepts are "Chuanjing" (Transmission through Meridians) and "Zhizhong" (Direct Invasion). Chuanjing refers to the pathogen transmitting from the Taiyang (Greater Yang) meridian to the Yangming (Yang Brightness) meridian, from Yangming to Shaoyang (Lesser Yang), from Shaoyang to Taiyin (Greater Yin), from Taiyin to Shaoyin (Lesser Yin), and from Shaoyin to Jueyin (Terminal Yin). This is called Xunjingchuan (Sequential Transmission along the Meridians). There is also Yuejingchuan (Cross-Meridian Transmission), such as when cold pathogens initially invade the Taiyang meridian but do not transmit to Yangming, instead directly invading Shaoyang; or they do not invade the exterior of the Yangming meridian but directly enter the Yangming Fu-organs. There are cases where transmission goes from Yangming directly into its own Fu-organ without passing through Shaoyang; or from Shaoyang directly into the Stomach Fu-organ without passing through the Three Yin meridians. Some stop after transmitting through one or two meridians; some remain confined to a single meridian throughout. Although the pathways of transmission vary, they all fall under the category of Chuanjing. As for Zhizhong, it refers to pathogens bypassing the Yang meridians and directly attacking the Three Yin meridians. Attack on Taiyin indicates a shallow disease; attack on Shaoyin indicates a deep disease; attack on Jueyin indicates an even deeper disease. These are conditions requiring urgent warming. Pathogens transmitted through meridians manifest as Cold syndromes at the exterior and Heat syndromes upon entering the interior, unlike direct invasion pathogens which present only with Cold and no Heat. By first clarifying the distinction between Chuanjing and Zhizhong, one avoids indiscriminate use of Cold-cooling and Warming-tonifying formulas. Zhang Zhongjing's discussions in the Three Yin chapters are somewhat mixed; those who fail to examine this carefully are understandably confused and bewildered.
The four characters governing the treatment of Shanghan are Exterior (Biao), Interior (Li), Cold (Han), and Heat (Re). Taiyang and Yangming belong to the Exterior; Taiyin, Shaoyin, and Jueyin belong to the Interior; Shaoyang resides between the Exterior and Interior, termed Half-Exterior Half-Interior. When Shanghan transmits from Yang meridians, it constitutes Heat pathogens. When it does not transmit from Yang meridians but directly enters Yin meridians, it is termed Zhonghan (Cold Invasion), constituting Cold pathogens. These are essential points from predecessors. I further elucidate these using eight scenarios based on the four characters: regardless of how Shanghan changes, it never exceeds these eight categories. Shanghan symptoms include Exterior Cold, Interior Cold, Exterior Heat, Interior Heat, simultaneous Exterior and Interior Heat, simultaneous Exterior and Interior Cold, Exterior Cold with Interior Heat, and Exterior Heat with Interior Cold.
What is Exterior Cold? When Shanghan initially affects the Taiyang meridian, presenting with headache, fever, and aversion to cold, it is named Waigan (External Contraction). This corresponds to the classic description: "The body feels like burning charcoal; sweating disperses the heat." The principles for Yangming (Muscle-Releasing method) and Shaoyang (Harmonizing method) are the same.
What is Interior Cold? When Shanghan does not transmit via Yang meridians but directly enters Yin meridians, presenting with cold extremities, faint and thin pulse, and diarrhea with undigested food, it is named Zhonghan. This corresponds to Zhang Zhongjing's instruction for urgent warming, suitable for Sini Tang (Four Reversal Decoction).
What is Exterior Heat? If a person fails to conserve essence in winter, slight cold invades the muscles, brewing into heat, and manifests in spring due to warm Qi, it is named Wenbing (Warm Disease). If it manifests in summer due to hot Qi, it is named Rebings (Heat Disease). Symptoms include headache and fever, similar to typical Shanghan, but distinguished by lack of aversion to cold and presence of thirst. The *Shanghan Fu* states: "Warm and Heat diseases arise in Spring and Summer; one must use Chaihu (Bupleuri Radix) and Gegen (Puerariae Lobatae Radix) to release the muscle layer." Since the pathogen is at the exterior, Chaihu and Gegen are used; since heat is trapped in the muscles, Huangqin (Scutellariae Radix) and Zhimu (Anemarrhenae Rhizoma) are added as auxiliaries. This is a flexible application.
What is Interior Heat? When Shanghan gradually transmits to the interior, or in cases of Spring Warmth and Summer Heat diseases, Heat pathogens enter the interior, constituting Interior Heat. In Taiyin, fluids are diminished; in Shaoyin, there is dry throat and mouth; in Jueyin, there is excessive thirst. This corresponds to Zhang Zhongjing's instruction for urgent purgation, using Daxiehu Tang (Major Bupleurum Decoction) and the three Chengqi Decoctions (Chengqi Formulas).
What is simultaneous Exterior and Interior Heat? In Yangming Shanghan syndrome transmitting to its Fu-organ, heat steams both the external muscles and internal stomach, causing thirst and delirious speech. This is diffuse heat where pathogens have not yet condensed. Treatment uses Baihu Tang (White Tiger Decoction) to vent heat outward through the skin and clear the interior organs, achieving resolution of both exterior and interior. This differs from solidified heat pathogens in the intestines and stomach that can be cured solely by purgation. Typical Shanghan has this, and Warm diseases have it even more frequently; careful differentiation is required.
What is simultaneous Exterior and Interior Cold? When Shanghan involves cold pathogens at the exterior combined with direct invasion of cold into the interior, it is called Lianggan Hanzheng (Simultaneous Cold Invasion of Exterior and Interior). Zhang Zhongjing uses Mahuang Fuzi Xixin Tang (Ephedra, Aconite, and Asarum Decoction) for this.
What is Exterior Cold with Interior Heat? Consider Lianggan Rezhi (Simultaneous Heat Invasion): Day 1 involves Taiyang and Shaoyin simultaneously; Day 2 involves Yangming and Taiyin; Day 3 involves Shaoyang and Jueyin. If the Three Yang meridians present with Cold and the Three Yin meridians present with Heat, is this not Exterior Cold and Interior Heat? Also, Fire stagnating internally combined with external contraction presents as Exterior Cold with Interior Heat. Furthermore, extreme Fire excess may mimic Water transformation, presenting with internal heat closure and external aversion to cold. The exterior appears Cold while the interior is truly Heat; mistakenly administering Hot tonics will cause deterioration upon ingestion.
What is Exterior Heat with Interior Cold? If a person has inherent deficiency-Cold constitution but contracts Warm-Heat pathogens externally, this is Mark Heat and Root Cold; Cold-clearing agents should not be overused. Additionally, severe Cold below may force rootless, unanchored Fire upward, causing intense surface heat, with the patient desiring to sit in mud or water. The exterior appears Heat, but the interior is truly Cold; mistakenly administering Cold agents will endanger the stomach immediately.
Shanghan transformed syndromes are myriad, but ultimately do not exceed the four characters: Exterior, Interior, Cold, and Heat. Their variations are unpredictable, yet always governed by these eight phrases. I have devoted thirty years to studying this. Understanding lies in the heart, application in the hand. I now specifically point out and elucidate this; students must study it diligently!