大伤寒者。冬月天气严寒。水冰地冻。而成杀厉之气。体弱之人。触犯之者。中则即病
。名曰正伤寒。不即病者。乃寒邪藏于肌肤之间。伏于荣卫之内。至春因温暖之气而发者
名曰温病。至夏因暑热而发者名曰热病。虽曰伤寒。实为热病。凡治伤寒。必先辨明六经。
而后
。而诊之则尺寸俱浮。浮紧有力为伤寒。浮缓无力为伤风。而太阳经症可辨矣。太阳病已。
以次而传经。必传于胃。发于一三日之间。便觉目疼鼻干不得眠。日晡潮热。不恶寒而反恶
热者。乃太阳阳明胃经受病也。而诊之则尺寸俱长。长而微洪者脏病。长而沉数者腑病。而
阳明症可辨矣。阳明病已。以次而传经必传于胆。发于三四日之间。便觉胸胁痛而耳聋。寒
热呕而口为之苦。乃足少阳胆经受病也。而胗之则尺寸俱弦。弦而滑数者病发厥。弦而和者
病欲散。而少阳经病可辨矣。少阳病已。以次而传经必传于脾。发四五日间。便觉腹满或痛
。而咽喉干燥。大便不通。小便如常。或自利。手足温而渴者。为传经腑热。起无头疼发
热。但恶寒自利不渴。手足冷者。为直中阴经。乃是太阴脾经受病也。而胗之则尺寸俱沉。
沉实有力为里实热。沉迟无力为里虚寒。而太阴经症可辨矣。太阴病已。以次而传经必传于
肾。发于五六日间。便觉口燥舌干而渴。手足乍温乍冷。便秘谵语者为热。或泄泻清谷不渴
。手指甲而青者为寒。乃足少阴肾经受病也。而胗之则尺寸俱沉。沉实有力知其热。沉迟
无力别其寒。而少阴经症可辨矣。少阴病已。以次而传经必传于肝。发于六七日间。便觉烦
懑而囊缩。谵语而渴者为热。口吐涎沫小腹痛不渴。身冷如冰者为寒。乃足厥阴肝经受病也
。而胗之则尺寸俱沉。沉实有力是其热。沉迟无力定知寒浮缓者病自愈而厥阴经症可辨矣。
又有两感伤寒者何也。假如一日太阳与少阴俱病。头疼为太阳邪盛于表。口干烦满为少阴邪
盛于里。二日阳明与太阴俱病。身热谵语为阳明邪盛于表。不欲食腹满为太阴邪盛于里。三
日少阳与厥阴俱病。耳聋为少阳邪盛于表。囊缩而厥。为厥阴邪盛于里。若水浆不入。又
不知人者。六日死。以其一脏一腑同受其邪。此两感之所以不救也。然其间亦有轻重之不同
。表重于里者。宜先救其表。而后及于里。里重于表者。宜先救其里。而后及于表。此又
求于一生于万死之中。不得已而施治也。其不两感于寒。更不传经者。至七八日间。其本经
之邪渐遏。至十二日则精神清爽而自愈。然伤寒传经种种不同。未可执为一定之序。有始于
太阳。以次而传入阴经。而不传少阴者。或太阳不传阳明少阳。而即传少阴者。或不由阳经
而直入阴经者。或始终即在一经。而不传者。或二阳三阳同受而为合病者。或太阳阳明先后
受而为并病者。种种不一详。审而治可也。又有中寒一症。或卒。中天地之寒气。或口得寒
物直中阴经。六脉沉弱无力。身倦手足厥冷。口噤不语。非若伤寒之邪。循经渐深也。然真
正伤寒。与感冒伤寒。及似伤寒。而非伤寒者。何以辨之。盖寒者。冬月严凝。肃杀之气也
。自霜降以后。春分以前。皆属冬。此时感冒而即发者。乃为真正伤寒也。若冬伤于寒不即
病。至春分后而发者。名曰温病。其症发热咳嗽。身痛口渴不恶寒。其脉弦数不紧。右手反
盛于左手。盖怫然在内故也。冬伤于寒春亦不病。到夏至后而发者。名曰热病其脉洪数。其
症热渴。比春更甚。温热二症俱不恶寒而渴。不恶寒则病非外来。渴则热自内达于表间。有
恶寒者。乃冒非时暴寒。非若冬月之甚也。其有不因冬伤于寒。而春自伤于风。夏自伤于暑
者。则自有伤风伤暑之别。而又不可以温热并论矣。或有感于天行时气。而病相同者。谓之
温疫。其症头疼身痛。发寒发热。一家一方长幼传染者是也。或足膝等处忽然红肿。或软弱
发热头疼。谓之香港脚伤寒。或心腹饱闷。呕逆头疼。发热恶寒。右手关脉紧盛。左手三奇和
平。而身不痛者。是伤食也若头痛而身亦痛左右手俱紧盛。谓之夹食伤寒。左手脉来紧盛。
右手洪滑。或寸脉沉伏。身热恶寒。隐隐头痛。喘咳烦闷。胸胁体痛。是夹痰伤寒。头痛发
热恶寒。但右手脉来空虚。左手脉来紧盛。是劳力伤寒。左手脉来紧涩。右手脉沉芤。心胸
胁下小腹有痛处。汗至胫而回。是蓄血伤寒。太阳症则如狂。阳明症则善忘。少阳症则寒热
似疟。此皆类伤寒。而非伤寒也。其余伤寒中杂症颇多。不能枚举。皆诸病门中所有者。但
杂症一兼伤寒。即所谓伤寒杂症。医者以意求之。则不言而自喻矣。
大伤寒，是指冬季天气严寒，水结冰、地冻裂，从而形成具有杀伤力的厉气。体质虚弱的人，如果触犯了这种邪气，中邪后立刻发病，称为“正伤寒”。如果没有立刻发病，那么寒邪就会潜伏在肌肤之间，藏匿于营卫之内，等到春季遇到温暖的气候而发作的，称为“温病”；等到夏季因暑热气候而发作的，称为“热病”。虽然统称为伤寒，但实际上属于热病范畴。凡是治疗伤寒，必须先辨明六经（太阳、阳明、少阳、太阴、少阴、厥阴）的证候，然后才能进行诊断。
诊察脉象时，如果寸关尺三部脉都浮，且浮紧有力，这是伤寒；如果浮缓无力，这是伤风。这样太阳经的证候就可以辨别了。太阳病结束后，病邪依次传变，必定传入胃经（阳明经）。通常在发病后一两天内出现，患者会感到眼睛疼痛、鼻子干燥、无法安睡，到了傍晚（日晡）出现潮热，不恶寒反而恶热，这是太阳和阳明胃经受病。诊察脉象时，寸关尺三部脉都长，脉长而微洪的是脏病，脉长而沉数的是腑病，这样阳明经的证候就可以辨别了。
阳明病结束后，病邪依次传变，必定传入胆经（少阳经）。通常在发病后三到四天内出现，患者会感到胸胁疼痛、耳聋，忽冷忽热、呕吐且口苦，这是足少阳胆经受病。诊察脉象时，寸关尺三部脉都弦，脉弦而滑数的是病发厥逆，脉弦而柔和的是病欲消散，这样少阳经的病证就可以辨别了。
少阳病结束后，病邪依次传变，必定传入脾经（太阴经）。通常在发病后四到五天内出现，患者会感到腹部胀满或疼痛，咽喉干燥，大便不通，小便正常，或者自利（腹泻），手足温暖且口渴，这是传经腑热。如果起病就没有头痛发热，只是恶寒、自利且不渴，手足冰冷，这是直中阴经，乃是太阴脾经受病。诊察脉象时，寸关尺三部脉都沉，脉沉实有力的是里实热，脉沉迟无力的是里虚寒，这样太阴经的证候就可以辨别了。
太阴病结束后，病邪依次传变，必定传入肾经（少阴经）。通常在发病后五到六天内出现，患者会感到口燥舌干且口渴，手足时而温暖时而寒冷，便秘且胡言乱语（谵语）的是热证，或者泄泻清谷（完谷不化）且不渴，手指甲发青的是寒证，这是足少阴肾经受病。诊察脉象时，寸关尺三部脉都沉，脉沉实有力可知是热，脉沉迟无力可别出是寒，这样少阴经的证候就可以辨别了。
少阴病结束后，病邪依次传变，必定传入肝经（厥阴经）。通常在发病后六到七天内出现，患者会感到烦闷且阴囊收缩，胡言乱语且口渴的是热证，口吐涎沫、小腹痛且不渴，身体冷如冰的是寒证，这是足厥阴肝经受病。诊察脉象时，寸关尺三部脉都沉，脉沉实有力是其热，脉沉迟无力定知是寒，脉浮缓则是病自愈，这样厥阴经的证候就可以辨别了。
又有两感伤寒是怎么回事呢？假如第一天太阳经与少阴经同时受病，头疼是因为太阳邪气盛于体表，口干烦满是因少阴邪气盛于体内。第二天阳明经与太阴经同时受病，身热谵语是因阳明邪气盛于体表，不想进食、腹部胀满是因太阴邪气盛于体内。第三天少阳经与厥阴经同时受病，耳聋是因少阳邪气盛于体表，阴囊收缩且四肢厥冷是因厥阴邪气盛于体内。如果出现不能进水浆，且神志不清不认识人的情况，六天后会死亡。因为一脏一腑同时受邪，这就是两感伤寒之所以难以救治的原因。然而其中也有轻重的不同。如果表证重于里证，应当先救表，然后再治里；如果里证重于表证，应当先救里，然后再治表。这又是为了在万死之中寻求一生，不得已而采取的治疗措施。
那些没有两感于寒，且不传经的，到了七八天，本经的邪气逐渐被遏制，到了十二天精神清爽而自愈。然而伤寒传经的情况种种不同，不可以固执地认为有一个固定的顺序。有的始于太阳经，依次传入阴经，但不传少阴经的；或者太阳经不传阳明、少阳，而直接传少阴经的；或者不由阳经直接入阴经的；或者始终只在一经而不传变的；或者二阳、三阳同时受邪而为合病的；或者太阳、阳明先后受邪而为并病的。情况种种不一，详细审察后进行治疗即可。
又有中寒这一症候，有的是突然遭受天地间的寒气侵袭，有的是吃了寒凉食物导致寒邪直中阴经。此时六脉沉弱无力，身体疲倦，手足厥冷，牙关紧闭不能说话。这与伤寒之邪循经逐渐深入不同。
那么，真正的伤寒，与感冒伤寒，以及似伤寒而非伤寒者，如何辨别呢？寒，是冬季严酷凝结、肃杀之气。从霜降以后到春分以前，都属于冬季。此时感冒后立即发病的，才是真正伤寒。如果在冬天受了寒邪但没有立刻发病，等到春分后才发作的，称为温病。其症状为发热、咳嗽、身体疼痛、口渴、不恶寒，脉象弦数而不紧，右手脉反而强于左手，这是因为郁热在内所致。如果在冬天受了寒邪，春天也不发病，到了夏至后才发作的，称为热病。其脉象洪数，症状为热、渴，比春季的更严重。温热两种病症都不恶寒而口渴，不恶寒说明病非外来，口渴说明热由内达于体表。如果有恶寒的，那是冒犯了非时节的暴寒，不像冬季那么严重。
那些不是因为冬天受寒，而是春天自己伤了风，夏天自己伤了暑的，则自有伤风、伤暑的区别，又不可以混同于温热病来讨论。或者有感受天时流行疫气，而病症相同的，称为温疫。其症状为头疼、身体疼痛、发寒发热，一家一户、长幼互相传染的就是这类。或者足膝等处忽然红肿，或者软弱、发热、头疼，称为香港脚伤寒（脚气）。或者心腹饱闷、呕逆、头疼、发热恶寒，右手关脉紧盛，左手三部脉平和，且身体不痛的，这是伤食。如果头痛且身体也痛，左右手脉俱紧盛，称为夹食伤寒。左手脉来紧盛，右手脉洪滑，或者寸脉沉伏，身热恶寒，隐隐作痛，喘咳烦闷，胸胁身体疼痛，这是夹痰伤寒。头痛、发热、恶寒，但右手脉来空虚，左手脉来紧盛，这是劳力伤寒。左手脉来紧涩，右手脉沉芤，心胸胁下小腹有痛处，汗出至小腿而回，这是蓄血伤寒。太阳经证则如狂，阳明经证则善忘，少阳经证则寒热似疟。这些都是类伤寒，而非真正的伤寒。
其余伤寒中的杂症很多，不能一一列举，都是其他病门中已有的内容。只要杂症兼有伤寒，就是所谓的伤寒杂症，医者凭心意推求，就不言自明了。
Da Shanghan (Major Cold Damage) refers to the condition where, during the severe cold of winter, water freezes and the ground cracks, forming a lethal qi (vital energy/pathogenic factor). Individuals with weak constitutions who are exposed to this pathogen will fall ill immediately upon infection, which is termed Zheng Shanghan (True Cold Damage). If illness does not occur immediately, the cold pathogen hides between the skin and muscles, lying dormant within Ying (Nutritive Qi) and Wei (Defensive Qi). When spring's warm air arrives, it may manifest as Wenbing (Warm Disease); if it manifests in summer due to summer-heat, it is called Rebing (Heat Disease). Although collectively referred to as Shanghan, they are essentially Heat Diseases. In treating Shanghan, one must first differentiate the Six Channels (Taiyang, Yangming, Shaoyang, Taiyin, Shaoyin, Jueyin), and only then proceed with diagnosis.
Upon pulse diagnosis, if the Cun, Guan, and Chi positions at both wrists are floating, and the pulse is floating, tight, and forceful, it indicates Shanghan; if it is floating, slow, and weak, it indicates Shangfeng (Wind Strike). Thus, the syndromes of the Taiyang Channel can be identified. After the Taiyang disease resolves, the pathogen transmits sequentially, inevitably entering the Stomach Channel (Yangming Channel). This typically occurs within one to three days, presenting with eye pain, nasal dryness, insomnia, tidal fever in the late afternoon (Ribu), aversion to heat rather than cold. This indicates pathology in the Taiyang and Yangming Stomach Channels. Pulse diagnosis reveals long pulses at all positions; a long and slightly surging pulse indicates Zang (Organ) disease, while a long and deep-rapid pulse indicates Fu (Hollow Organ) disease. Thus, Yangming syndromes can be identified.
After Yangming disease resolves, transmission proceeds to the Gallbladder Channel (Shaoyang Channel). Occurring within three to four days, symptoms include chest and hypochondriac pain, deafness, alternating chills and fever, vomiting, and bitter taste in the mouth. This indicates pathology in the Foot-Shaoyang Gallbladder Channel. Pulse diagnosis shows wiry pulses at all positions; a wiry, slippery, and rapid pulse indicates the onset of Jue (reversal/cold limbs), while a wiry and harmonious pulse indicates the disease is resolving. Thus, Shaoyang syndromes can be identified.
After Shaoyang disease resolves, transmission proceeds to the Spleen Channel (Taiyin Channel). Occurring around four to five days, symptoms include abdominal fullness or pain, dry throat, constipation, normal urination, or spontaneous diarrhea, warm hands and feet, and thirst. This indicates transmitted Fu-heat. If there is no headache or fever initially, but only aversion to cold, spontaneous diarrhea without thirst, and cold hands and feet, it is "Direct Invasion of Yin Channels," indicating pathology in the Taiyin Spleen Channel. Pulse diagnosis shows deep pulses at all positions; a deep, solid, and forceful pulse indicates interior excess-heat, while a deep, slow, and weak pulse indicates interior deficiency-cold. Thus, Taiyin syndromes can be identified.
After Taiyin disease resolves, transmission proceeds to the Kidney Channel (Shaoyin Channel). Occurring around five to six days, symptoms include dry mouth and tongue with thirst, and hands and feet that alternate between warm and cold. Constipation with delirium indicates heat; diarrhea with undigested food, no thirst, and blueish fingernails indicate cold. This indicates pathology in the Foot-Shaoyin Kidney Channel. Pulse diagnosis shows deep pulses at all positions; deep, solid, and forceful indicates heat, while deep, slow, and weak indicates cold. Thus, Shaoyin syndromes can be identified.
After Shaoyin disease resolves, transmission proceeds to the Liver Channel (Jueyin Channel). Occurring around six to seven days, symptoms include irritability and retraction of the testicles. Delirium with thirst indicates heat; salivation, lower abdominal pain without thirst, and body cold as ice indicate cold. This indicates pathology in the Foot-Jueyin Liver Channel. Pulse diagnosis shows deep pulses at all positions; deep, solid, and forceful indicates heat, deep, slow, and weak indicates cold, and floating-slow indicates spontaneous recovery. Thus, Jueyin syndromes can be identified.
What is Lianggan Shanghan (Double-Infection Cold Damage)? For example, on the first day, both Taiyang and Shaoyin channels are affected: headache indicates excessive Taiyang pathogen on the exterior; dry mouth and irritability/fullness indicate excessive Shaoyin pathogen on the interior. On the second day, both Yangming and Taiyin are affected: body heat and delirium indicate excessive Yangming pathogen on the exterior; anorexia and abdominal fullness indicate excessive Taiyin pathogen on the interior. On the third day, both Shaoyang and Jueyin are affected: deafness indicates excessive Shaoyang pathogen on the exterior; testicular retraction and cold limbs indicate excessive Jueyin pathogen on the interior. If the patient cannot take fluids and loses consciousness, death occurs after six days because one Zang and one Fu organ are simultaneously infected by the pathogen; this is why Lianggan is incurable. However, severity varies. If exterior syndrome is heavier than interior, treat the exterior first, then the interior. If interior is heavier, treat the interior first, then the exterior. This is a desperate measure to save life from death.
For those not suffering from double-infection and without transmission, by the seventh or eighth day, the pathogen in the primary channel is gradually suppressed, and by the twelfth day, mental clarity returns, and the disease heals spontaneously. However, transmission patterns vary and should not be rigidly fixed. Some start in Taiyang and transmit to Yin channels without involving Shaoyin; some skip Yangming and Shaoyang to involve Shaoyin directly; some bypass Yang channels entirely to enter Yin channels; some remain confined to one channel; some involve simultaneous infection of two or three Yang channels (Hebing/Combined Disease); some involve sequential infection of Taiyang and Yangming (Bingbing/Concurrent Disease). These cases require careful differentiation and treatment.
There is also Zhonghan (Cold Strike), caused suddenly by heaven-earth cold qi or ingestion of cold substances directly invading Yin channels. The six pulses are deep, weak, and powerless; the body is fatigued, hands and feet are cold, jaw is locked, and speech is impaired. This differs from Shanghan, where the pathogen penetrates gradually along the channels.
How to distinguish True Shanghan from Ganmao Shanghan (Common Cold-type Cold Damage) and Lei Shanghan (Shanghan-like conditions)? Han (Cold) is the severe, killing qi of winter. From Shuangjiang (Frost Descent) to Chunfen (Spring Equinox), any immediate illness after exposure is True Shanghan. If cold is contracted in winter but manifests after Chunfen, it is Wenbing (Warm Disease), with symptoms of fever, cough, body ache, thirst, no aversion to cold, wiry-rapid non-tight pulse, and right-hand pulse stronger than left due to internal constraint. If contracted in winter but manifests after Xiazhi (Summer Solstice), it is Rebing (Heat Disease), with surging-rapid pulse and more severe heat/thirst than in spring. Both Warm and Heat diseases feature thirst without aversion to cold, indicating internal heat reaching the surface. Aversion to cold suggests exposure to sudden abnormal cold, less severe than winter cold.
If illness arises from spring wind or summer summer-heat independently, it is distinct from Warm/Heat diseases. If contracted from epidemic qi with similar symptoms, it is Wenyi (Warm Epidemic), characterized by headache, body ache, chills/fever, and family contagion. Sudden redness/swelling of legs/knees or weakness/fever/headache is Hongxiangjiao Shanghan (Hongxiangjiao Cold Damage, i.e., Beriberi). Fullness in heart/abdomen, vomiting, headache, fever, aversion to cold, tight-full Guan pulse on right,平和 Pinghe (harmonious) pulses on left, and no body pain indicate Shangshi (Food Injury). Headache with body pain and tight pulses on both hands is Jiashi Shanghan (Shanghan with Food Retention). Tight left pulse, surging-slippery right pulse, or deep-fu Cun pulse, with fever, aversion to cold, vague headache, wheezing/cough, irritability, and chest/hypochondriac/body pain indicates Jiatan Shanghan (Shanghan with Phlegm). Headache, fever, aversion to cold, empty right pulse, and tight left pulse indicates Laoli Shanghan (Shanghan from Overwork). Tight-severe left pulse, deep-kou right pulse, pain in chest/abdomen, and sweat returning below knees indicates Xuxue Shanghan (Shanghan with Blood Stasis). Taiyang syndrome presents like mania; Yangming syndrome presents with forgetfulness; Shaoyang syndrome presents with chills/fever resembling malaria. These are Lei Shanghan (Shanghan-like), not true Shanghan.
Other miscellaneous disorders within Shanghan are numerous and listed in other sections. When miscellaneous disorders coexist with Shanghan, they are termed Shanghan Zazheng (Miscellaneous Disorders with Shanghan). Physicians should deduce the nature through clinical reasoning.