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。
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.