肾属寒水。主令在冬。故内经以为闭蛰封藏之本。以欲耗其精。则不能奉若天时。封藏
固密。遂致太阳疏渗。寒邪易侵。若肾脏坚固。即使迫于寒灭受邪轻浅。治之即痊。肾脏虚衰。
略冒寒邪。便尔深重。医药难疗故曰。伤寒偏死肾虚人。良非虚语。
伤寒传变淆讹。症端错杂。且肃杀之气。最为毒烈医者不能博古衡今。漫投汤剂。鲜不
夭枉。致令愤激之说。以不服药为中医。岂其然哉。惟正气实而邪气轻者。或可俟其经尽而愈
。若正气虚而邪气重者。非按法施治。何由得痊。譬如人溺洪涛。命在呼吸。不为援手。而
听其自渡。恐全活者几希矣。
一曰太阳受之。即与少阴俱病。则头痛。（太阳）口干。烦满而渴。（少阴）二日阳明受之
。即与太阴俱病。则身热谵语（阳明）腹满不欲食。（太阴）三日少阳受之。即与厥阴俱病。则耳聋
。（少阳）囊缩而厥。（厥阴）病至六日。腑脏之气俱尽。营卫之气俱绝。则死矣。仲景既论两
感为必死之症。而复日治有先后者。盖不忍坐视。而觊其万一之活也。如下利身痛。则先救
里。不利身痛。则先救表。表症多者发表为急。里症多者。
攻里为先。东垣曰。虚而感之深者必死。实而感之浅者或生。用大羌活汤。十救一二。
春应暖而反寒。夏应热而反凉。秋应凉而反热。冬应寒而反温。非其时而有其气。触冒
之者。沿门遍户。长幼相似。此时行疫症也。春感寒邪。升麻葛根汤。夏感凉邪。调中汤。秋感
热邪。苍术白虎汤。冬感温邪。葳蕤汤。表不愈者。芎苏散。里不愈者。调胃承气汤。或
成大头瘟者。当辨其经。先于鼻额红肿。以致面目肿盛。阳明也。壮热气喘。口干咽痛。脉
数而大。普济消毒饮。耳旁及头角红肿少阳也。往来寒热潮热。口苦咽干。目痛胁痛。小柴
胡汤。加花粉芩翘。发于项上。及脑后项下。目后赤肿者。太阳也。荆芥败毒散。三阳俱受
邪。普济消毒饮。不可峻攻。恐邪气内陷也。虚人兼扶正气。便结者微下之。
肾脏五行属寒水，其主令的季节在冬季。因此，《黄帝内经》将其视为闭藏蛰伏、封固储藏的根本。如果因房事过度耗损肾精，就不能顺应天时的变化，导致封藏功能不坚固致密，进而致使太阳经疏泄渗利失常，寒邪容易侵袭人体。如果肾脏功能坚固，即使受到严寒逼迫而受邪，病情也轻浅，治疗即可痊愈。如果肾脏虚衰，稍微冒犯寒邪，病情就会变得深重，医药难以治愈，所以说“伤寒偏死肾虚人”，这确实不是虚妄之语。
伤寒病的传变过程混乱且易出错，症状表现错综复杂。况且肃杀之气（寒邪）最为毒烈，医生如果不能博通古今、权衡利弊，随意投用汤药，很少有不夭折枉死的。这就导致了“不服药为中医（最高明的治疗）”的愤激之说。难道真是这样吗？只有正气充实而邪气轻微的，或许可以等待经络病尽而自愈。如果正气虚弱而邪气深重的，不按法则施治，怎么能痊愈呢？这就好比人落入洪涛之中，性命只在呼吸之间，如果不伸手救援，而听凭其自行渡过，恐怕能保全活命的人极少。
第一种情况是：太阳经受邪，随即少阴经也发病，表现为头痛（太阳经证）、口干、烦闷而渴（少阴经证）。第二天阳明经受邪，随即太阴经也发病，表现为身热、谵语（阳明经证）、腹部胀满、不想进食（太阴经证）。第三天少阳经受邪，随即厥阴经也发病，表现为耳聋（少阳经证）、阴囊收缩、四肢厥冷（厥阴经证）。病至第六天，脏腑之气耗尽，营卫之气断绝，就会死亡。张仲景既然论述了两感病（表里两经同时受邪）为必死的病症，却又说治疗有先后顺序，大概是不忍心坐视病人死亡，而希望有一线生机。如下利且身体疼痛，则先救里；不下利但身体疼痛，则先救表。表证多的，解表为急；里证多的，攻里为先。李东垣说：体质虚弱而感邪深的必然死亡，体质实壮而感邪浅的或许能生。使用大羌活汤，十人中能救一二。
春天应该温暖却反而寒冷，夏天应该炎热却反而凉爽，秋天应该凉爽却反而炎热，冬天应该寒冷却反而温暖。非其时而有其气，触犯这种气候的人，家家户户，长幼皆相似，这就是时行疫症。春天感受寒邪，用升麻葛根汤；夏天感受凉邪，用调中汤；秋天感受热邪，用苍术白虎汤；冬天感受温邪，用葳蕤汤。表证不愈的，用芎苏散；里证不愈的，用调胃承气汤。或者发展成“大头瘟”的，应当辨别所属经络。先是鼻部和额头红肿，以致面目肿胀盛大，这是阳明经证，壮热气喘，口干咽痛，脉数而大，用普济消毒饮。耳旁及头角红肿，这是少阳经证，往来寒热，潮热，口苦咽干，目痛胁痛，用小柴胡汤，加天花粉、黄芩、连翘。发于项上及脑后项下，目后赤肿的，这是太阳经证，用荆芥败毒散。三阳经俱受邪的，用普济消毒饮，不可峻猛攻下，恐邪气内陷。体虚之人兼扶正气，大便结滞的轻微攻下。
The Kidney belongs to Cold Water. Its governing season is Winter. Therefore, the *Neijing* (Inner Canon) regards it as the root of closure, hibernation, and storage. If essence is depleted by sexual indulgence, one cannot conform to the changes of Heaven and Earth, leading to a lack of firmness and density in storage and consolidation. Consequently, the Taiyang channel becomes lax and permeable, making it easy for Cold pathogenic factors to invade. If the Kidneys are solid, even if pressed by severe cold and affected by pathogens, the condition will be superficial, and treatment will lead to recovery. If the Kidneys are deficient and declining, merely encountering Cold pathogenic factors will result in a deep and severe condition, difficult to treat with medicine. Thus it is said, "In Shanghan (Cold Damage), those with Kidney deficiency are more likely to die," which is indeed not an empty statement.
The transmission and transformation of Shanghan are chaotic and prone to error, with symptoms being complex and mixed. Moreover, the肃杀 (desolating/killing) Qi, which is most toxic and fierce, requires physicians to possess broad knowledge of the past and present to weigh circumstances. If they arbitrarily administer decoctions, few will avoid premature death. This has led to the resentful saying that "not taking medicine is the best medical treatment." Is this really the case? Only when Zhengqi (Upright Qi) is substantial and Xieqi (Pathogenic Qi) is light might one wait for the meridians to exhaust the pathogen and recover naturally. If Zhengqi is deficient and Xieqi is heavy, how can one recover without following specific methods of treatment? It is like a person drowning in a flood, with life hanging in the balance; if no hand is extended to help, but left to swim on their own, few will survive.
One scenario is: When the Taiyang channel is affected, Shaoyin simultaneously suffers. This presents with headache (Taiyang symptom), dry mouth, vexation, fullness, and thirst (Shaoyin symptom). On the second day, Yangming is affected, and Taoyin simultaneously suffers. This presents with body heat, delirious speech (Yangming symptom), abdominal fullness, and loss of appetite (Taoyin symptom). On the third day, Shaoyang is affected, and Jueyin simultaneously suffers. This presents with deafness (Shaoyang symptom), retraction of the scrotum, and cold limbs (Jueyin symptom). By the sixth day, the Qi of the Zang-Fu organs is exhausted, and the Ying (Nutritive) and Wei (Defensive) Qi are severed, leading to death. Zhang Zhongjing discussed "Lianggan" (Simultaneous Affection of Exterior and Interior channels) as a fatal condition, yet also stated that treatment has priorities. This is likely out of reluctance to watch patients die, hoping for a sliver of survival. For example, if there is diarrhea and body pain, first rescue the Interior; if there is no diarrhea but body pain, first rescue the Exterior. If Exterior symptoms predominate, releasing the Exterior is urgent; if Interior symptoms predominate, purging the Interior takes precedence. Li Dongyuan said: Those who are deficient and deeply affected will surely die; those who are substantial and lightly affected may live. Using Da Qianghuo Tang (Major Notopterygium Decoction), one or two out of ten may be saved.
Spring should be warm but is instead cold; Summer should be hot but is instead cool; Autumn should be cool but is instead hot; Winter should be cold but is instead warm. Having Qi contrary to the season, those who encounter it affect households across the neighborhood, young and old alike. This is Shixing Yizheng (Seasonal Epidemic Disease). Spring Cold damage uses Shengma Gegen Tang (Cimicifugae and Puerariae Decoction); Summer Cool damage uses Tiaozhong Tang (Regulating the Middle Decoction); Autumn Heat damage uses Cangzhu Baizhu Tang (Atractylodis Macrocephalae and White Tiger Decoction); Winter Warm damage uses Weirui Tang (Anemarrhenae Decoction). If Exterior symptoms persist, use Xiong Su San (Sichuan Lovage and Perilla Powder); if Interior symptoms persist, use Tiaowei Chengqi Tang (Regulating the Stomach and Directing Downward Decoction). If it develops into Datouwen (Great Head Plague), one must differentiate the channel. Initially, redness and swelling of the nose and forehead, leading to severe facial swelling, indicate Yangming channel involvement: high fever, panting, dry mouth, sore throat, rapid and large pulse. Use Puji Xiaodu Yin (Universal Benefit Detoxification Decoction). Redness and swelling around the ears and temporal angles indicate Shaoyang channel involvement: alternating chills and fever, tidal fever, bitter taste, dry throat, eye pain, and hypochondriac pain. Use Xiao Chaihu Tang (Minor Bupleurum Decoction) plus Tianhuafen (Trichosanthes Root), Huangqin (Scutellaria Root), and Lianqiao (Forsythia Fruit). Redness and swelling behind the eyes, occurring at the nape and back of the neck, indicate Taiyang channel involvement. Use Jingjie Baidu San (Schizonepeta and Antidote Powder). If all three Yang channels are affected, use Puji Xiaodu Yin. Do not use harsh purgatives, lest the pathogen sink inward. For deficient individuals, support Zhengqi concurrently. If constipation occurs, use mild purgation.