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Translation:
It is said that cold damage (Shanghan, a category of febrile diseases caused by exogenous pathogens) occurs in all four seasons, but its treatment cannot be generalized. In winter, the climate is cold, and the cou li (skin pores and interstitial spaces) are tight and dense; therefore, acrid-sweet-warm herbs are indispensable, so Guizhi Tang (Cinnamon Twig Decoction) and similar formulas are used for treatment. However, wind and cold pathogens often influence each other. If cold damages the Ying blood (nutritive qi circulating within the vessels), presenting with aversion to cold, headache, a floating-tight pulse, and absence of sweating, Mahuang Tang (Ephedra Decoction) is employed to open the cou li and disperse the pathogen; recovery follows once sweating occurs. If wind damages the Wei qi (defensive qi circulating outside the vessels), presenting with headache, aversion to wind, a floating-slow pulse, and spontaneous sweating, Guizhi Tang is used to secure the cou li and disperse the pathogen; recovery follows once sweating ceases. The Classics state: "Acrid and sweet substances act as Yang to disperse," which refers to this principle. As for cases where both Ying and Wei are damaged, these two formulas are insufficient. Da Qinglong Tang (Major Blue Green Dragon Decoction) must be used. However, this formula is too potent and not suitable for average practitioners; I have devised alternatives. Winter represents true Shanghan, when the weather is severely cold and frozen, and wind-cold is fierce. Those who contract it must be treated with acrid-warm herbs to disperse. Outside of winter, patients may also present with aversion to cold and headache; these should be treated with acrid-cool agents to unblock the exterior and harmonize the interior, leading to recovery. Using acrid-warm herbs like those in Guizhi Tang, intended for winter, to treat such conditions indiscriminately would result in many deaths. What constitutes acrid-cool? It is Qianghuo Chonghe Tang (Notopterygium Harmonizing Decoction). This formula can safely substitute for Da Qinglong Tang. Alas! One formula replaces three dangerous ones.

Commentary: The differentiation of medications for cold versus warm-summer diseases is very clear. Chonghe Tang is particularly an accurate remedy for both warm and cool syndromes, effective in every instance.

It is said: *Huo Ren Shu* (Book of Vitality) states regarding warm disease: "Yang heat is not yet abundant, constrained by cold." But if latent cold has already transformed into warm disease, how can it still be called cold? How can it be said that cold constrains Yang heat? Furthermore, regarding heat disease: "Yang heat is already abundant, and cold cannot constrain it"; thus, it should no longer be referred to as cold. Generally, in spring and summer, Yang heat transforms the latent cold; there is no cold capable of constraining Yang heat. External cold pathogens that can injure Yang Qi constitute "epidemic cold illness" (Shixing Hanji). This is what Zhang Zhongjing described as "epidemic cold plague" (Shixing Hanyi): sudden cold weather after the Spring Equinox and before the Autumn Equinox. In the third and fourth lunar months, Yang Qi is still weak; when constrained by cold, the resulting fever is mild. In the fifth and sixth months, Yang Qi is abundant; when constrained by cold, the resulting fever is severe. In the seventh and eighth months, Yang Qi is declining; when constrained by cold, the resulting fever is also slight. Thus, it is known that the discussion on the waxing and waning of Yang Qi in epidemic cold illness aligns with that of warm and heat diseases. However, the discussion on the cold of sudden cold differs from the cold of latent cold that has already transformed; they are contradictory. If names are incorrect, speech does not flow smoothly. Zhang Zhongjing further stated: "The disease resembles warm disease and summerheat disease, but the treatment differs." The key lies in differentiating the disease source; distinguishing between cold, heat, and warm allows one to clearly determine whether to use cold or hot medications.

Commentary: Mr. Nanyang (Zhang Zhongjing) introduced the character "transform" (Bian), demonstrating great wisdom. Regarding the misconception of latent cold, Nan Weng (Ye Tianshi) clearly recognized the error but dared not openly refute it, fearing criticism from those adhering to traditional views. Instead, he categorized it as non-seasonal cold illness to dispel confusion. This originated with Li Dongyuan establishing the category of "cold plague," which serves to support the *Neijing* (Inner Canon) and enlighten future generations.