伤寒者，由冬令之寒邪，伤于寒水之经也。考诸贤之书，皆谓霜降之后，春分以前，有感触者，是为伤
寒。据六气而推之，似乎不然。盖霜降之后，犹是燥金主气，有感之者，是凉气也。如或天气大寒，即《
金匮》所谓未至而至也，春分以前，正是风木司权，有感之者，是风邪也，如或天气大寒，即《金匮》
所谓至而不去也，若此则界限分矣。其实伤寒之病，确在乎立冬之后，寒水主政之时，一交春令，风木主政，
便不可以伤寒名之。即有寒热为病，与伤寒相似者，便是先贤所谓春应温而反寒，寒疫之病也。夫伤寒之
为病，头疼身痛，寒热无汗，脉来浮紧者，宜用辛散太阳法去前胡、红枣，加紫苏、葱白治之，如体
实邪盛者，仲圣麻黄汤亦可用之。若果有汗，脉浮而缓，便是伤风之病，倘误用之，变证蜂起矣。此略述寒
邪初伤太阳寒水之经之证也。其传经、两感，合痛、并病，及误治、变证、坏证，仲景书中细详，可毋重赘。
丰尝谓凡学时病者，必须参读仲景《伤寒论》，庶可融会贯通，否则不可以言医也。
中寒者，交一阳之后，时令过于严寒，突受寒淫杀厉之气，卒然腹痛，面青吐泻，四肢逆冷，手足挛蜷，
或昏闭身凉，或微热不渴等证。丹溪曰∶仓卒中寒，病发而暴，难分经络，温补自解，斯说似乎灭裂，其实
有三阴之别焉。盖太阴中寒，则脘中作痛，少阴则脐腹作痛，厥阴则少腹作痛。见证既分，更当审其脉象，
如沉缓中太阴，沉细中少阴，沉迟中厥阴，若此别之，庶几导 。如果脉微欲绝，昏不知人，问之不能答，
似此难分经络，始可遵丹溪用温补之剂，急拟挽正回阳法治之。三阴
中寒，皆以甘热祛寒法治之。若寒中太阴，以干姜为君，少阴以附子为君，厥阴以吴萸为君。吐甚加藿香、豆
蔻，泻甚加苍术、木香，筋挛者佐以木瓜、橘络，呃逆者佐以柿蒂、丁香。临证之间，切宜细辨而治，庶无贻误。
伤寒，是由冬季的寒邪侵袭足太阳膀胱经（寒水之经）所致。考察前贤的著作，都认为在霜降之后、春分之前感受外邪，才称为伤寒。但如果依据六气主令来推究，似乎并非如此。因为霜降之后，仍然是燥金之气主令，此时感受的外邪属于凉气。如果天气突然大寒，这就是《金匮要略》所说的“未至而至”（时令未到而寒气先至）。春分之前，正是风木之气主令，此时感受的外邪属于风邪；如果天气持续大寒，这就是《金匮要略》所说的“至而不去”（时令已到而寒气滞留）。像这样界限就分明清楚了。其实，真正的伤寒病，确实发生在立冬之后、寒水之气当令的时候；一旦进入春季，风木之气当令，就不能再称为伤寒了。即使有出现寒热症状且与伤寒相似的疾病，那也是先贤所说的“春天本应温暖却反而寒冷”所导致的寒疫。
至于伤寒这种病，表现为头痛身痛、恶寒发热、无汗、脉象浮紧的，适宜使用辛温发散太阳经的方法治疗，方中去掉前胡和红枣，加入紫苏和葱白；如果是体质壮实、邪气盛者，张仲景的麻黄汤也可以使用。如果确实有汗出，脉象浮而缓，那就是伤风病，倘若误用上述治法，就会变证蜂拥而起。这里只是简要叙述寒邪初伤太阳寒水之经的证候。至于传经、两感、合病、并病，以及误治、变证、坏证等情况，张仲景的书中已有详细记载，此处不必重复赘述。我曾说过，凡是学习时病的人，必须参考阅读张仲景的《伤寒论》，这样才能融会贯通，否则不足以谈论医学。
中寒，是在阳气初生之后，时令过于严寒，突然遭受寒湿杀厉之气侵袭，骤然出现腹痛、面色青暗、呕吐腹泻、四肢逆冷、手足拘挛蜷缩，或者昏迷闭窍、身体发凉，或者微热不渴等症状。朱丹溪说：“仓猝之中寒，发病急暴，难以分辨经络，通过温补即可自愈。”这种说法似乎过于粗略，其实中寒还有三阴经的区别。太阴中寒，则脘腹作痛；少阴中寒，则脐腹部作痛；厥阴中寒，则少腹部作痛。既然证候已经区分清楚，更应当审察其脉象，如脉沉缓属太阴中寒，脉沉细属少阴中寒，脉沉迟属厥阴中寒，像这样加以辨别，才能引导正确治疗。如果脉象微弱欲绝，昏迷不知人事，询问不能回答，像这样难以分辨经络归属时，才可以遵循朱丹溪的建议，使用温补药剂，紧急拟定挽正回阳法治之。三阴经的中寒，都用甘热祛寒法治之。若寒邪中于太阴，以干姜为君药；中于少阴，以附子为君药；中于厥阴，以吴茱萸为君药。呕吐严重者加藿香、豆蔻；腹泻严重者加苍术、木香；筋脉拘挛者辅以木瓜、橘络；呃逆者辅以柿蒂、丁香。临证之时，务必仔细辨证施治，才不会贻误病情。
Shanghan (Cold Damage) is caused by cold pathogenic factors in winter invading the Bladder Meridian of Foot-Taiyang (the meridian associated with Cold Water). Examining the works of past sages, it is generally stated that contracting an external pathogen after Frost's Descent and before the Spring Equinox constitutes Shanghan. However, deducing from the Six Qi theory, this seems incorrect. After Frost's Descent, Dryness Metal still governs the climate; those affected are exposed to Coolness Qi. If the weather becomes extremely cold, this corresponds to what is described in *Jin Gui Yao Lue* as "arriving before its time" (cold arriving before the solar term). Before the Spring Equinox, Wind Wood governs the climate; those affected are exposed to Wind Pathogens. If extreme cold persists, this corresponds to "lingering after its time" (cold lingering after the solar term). In this way, the boundaries are clearly distinguished. Actually, true Shanghan disease occurs strictly after Start of Winter, when Cold Water governs. Once spring arrives and Wind Wood governs, it can no longer be called Shanghan. Even if there are diseases with chills and fever resembling Shanghan, these are what ancient sages referred to as Han Yi (Cold Epidemic), caused by "spring should be warm but instead is cold."
Regarding Shanghan disease, characterized by headache, body ache, aversion to cold with fever, absence of sweating, and a floating-tight pulse, the appropriate treatment is the Acrid-Dispersing Method for Taiyang. The formula should remove Qian Hu (Peucedani Radix) and Hong Zao (Jujubae Fructus), and add Zi Su Ye (Perillae Folium) and Cong Bai (Allii Fistulosi Bulbus). For patients with robust constitution and excess pathogens, Zhang Zhongjing's Mahuang Tang (Ephedra Decoction) may also be used. If there is indeed sweating and the pulse is floating and moderate, it is a case of Shangfeng (Wind Strike); mistakenly applying the above treatments will lead to numerous transformation syndromes. This briefly describes the syndrome where cold pathogen initially invades the Taiyang Cold Water meridian. Regarding transmission through meridians, Liang Gan (simultaneous involvement of exterior and interior), He Bing (combined diseases), Bing Bing (concurrent diseases), as well as misdiagnosis, transformation syndromes, and ruined syndromes, Zhang Zhongjing's texts detail them thoroughly, so repetition here is unnecessary. I have often said that anyone studying Shi Bing (Seasonal Diseases) must consult Zhang Zhongjing's *Shanghan Lun* (Treatise on Cold Damage), so as to achieve comprehensive understanding; otherwise, one cannot claim proficiency in medicine.
Zhonghan (Mid-Cold) occurs after the generation of initial Yang, when the seasonal climate is excessively severe cold, and sudden exposure to killing-cold qi causes abrupt abdominal pain, cyanotic complexion, vomiting and diarrhea, cold limbs, curling of hands and feet, or coma with cold body, or slight fever without thirst. Zhu Danxi stated: "Sudden mid-cold presents abruptly and severely, making meridian differentiation difficult; warming and tonifying leads to self-resolution." This view seems overly simplistic, as there are distinctions among the Three Yin meridians. Taiyang Zhonghan manifests as epigastric/abdominal pain; Shaoyin Zhonghan manifests as periumbilical/abdominal pain; Jueyin Zhonghan manifests as hypogastric pain. Once the symptoms are differentiated, pulse diagnosis is essential: sinking-slow pulse indicates Taiyin Zhonghan, sinking-thin pulse indicates Shaoyin Zhonghan, and sinking-choppy pulse indicates Jueyin Zhonghan. Such differentiation guides proper treatment. If the pulse is faint and nearly imperceptible, accompanied by coma and inability to respond, making meridian differentiation impossible, then following Zhu Danxi's advice to use warming and tonifying formulas is appropriate, urgently employing methods to restore正气 (Righteous Qi) and return Yang. All Three-Yin Zhonghan cases are treated with Sweet-Warm methods to dispel cold. If cold strikes Taiyin, Gan Jiang (Zingiberis Rhizoma) serves as the sovereign herb; if Shaoyin, Fu Zi (Aconiti Lateralis Radix Praeparata) is sovereign; if Jueyin, Wu Zhu Yu (Evodiae Fructus) is sovereign. For severe vomiting, add Huo Xiang (Agastaches Herba) and Dou Kou (Amomi Fructus); for severe diarrhea, add Cang Zhu (Atractylodis Rhizoma) and Mu Xiang (Aucklandiae Radix); for muscle spasms, assist with Mu Gua (Chaenomelis Fructus) and Ju Luo (Citri Reticulatae Pericarpium Viride); for hiccups, assist with Shi Di (Diospyri Fructus Calyx) and Ding Xiang (Caryophylli Flos). During clinical practice, careful differentiation and treatment are crucial to avoid errors.