太阳属膀胱寒水，非发汗不能愈，亦有桂枝、麻黄以助阳祛邪。此膀胱寒水之经，有标本之作。
风寒初客，仍在表，宜用辛温之剂以发散之。若无头痛恶寒，或非冬时，皆不可用。
阳明属胃，非通泄不能痊，必用大黄、芒硝以疏利阳热。此言表证已罢，头痛恶寒已除，则热
归阳明之本矣，宜承气汤寒剂以泄热。若恶寒未除，则为表，寒邪尚在，不可下也。冬时亦宜用，
不可拘忌。
少阳属胆，无出入之道，柴胡、半夏能利能汗，消解血热，黄芩佐之。
太阴脾土，惟恶寒湿，非干姜、白术不能燥湿也。
少阴肾水，惟恶寒燥，非附子不能温润。
厥阴肝木，藏血荣筋，非芍药、甘草不能滋养。此用药经常之道也。
夫伤寒发表攻里之药，寒热殊途，用之一差，死生反掌。所以越人、仲景深致意于其间也。《难
经》云∶伤寒阳虚阴盛，汗之则愈，下之则死。阳盛阴虚，汗之则死，下之则愈。且寒邪之伤人也，
有浅深焉。浅者，汗之；深者，下之。此古今不易之定法也。方其风寒初客皮毛之间，阴气乃盛，
闭塞腠理，身中阳气已虚，不能御卫，遂有恶风恶寒之证见焉。当此之时，只宜桂枝汤辛甘温之药，
助阳抑阴而发之。阴邪既散，表气冲和而愈。经云辛甘发散为阳者是也。不知用此而反以承气汤苦
寒之药下之，表里俱伤，不亡何待？表邪既罢，寒作为热，阳陷入深而盛于里，则津液消耗，肠胃
燥涩，而脏腑之真阴虚矣。阴气既虚，即谵妄狂躁，烦渴恶热之病而作也。当此之时，宜用承气汤
苦寒之剂，扶阴抑阳而泄去热气，阳邪即退，胃中真阴来复，里气和平而愈。《内经》所谓酸苦涌
泄为阴者是也。不知用此，乃以桂枝辛热之药助邪伐正，安有不毙者乎？所以仲景云∶桂枝下咽，
阳盛则毙；承气入胃，阴盛乃亡。良以此夫。呜呼，此论诚为伤寒汗下之枢机乎？俗医不能达此为
妙，昧于阴阳虚盛之道，悖逆此理而不杀人也，几希。经云发表不远热，攻里不远寒，岂虚语哉！
The Taiyang channel belongs to the cold water of the Bladder (Bladder). It cannot be cured without inducing sweating; therefore, Guizhi Tang (Cinnamon Twig Decoction) and Mahuang Tang (Ephedra Decoction) are used to assist Yang Qi and dispel pathogenic factors. This discussion pertains to the manifestations at the Biao (Exterior/Mark) and Ben (Root/Internal) levels of the Bladder's cold water channel.
When Wind-Cold initially invades and remains in the Exterior, acrid-warm formulas should be used to disperse it. If there is no headache or aversion to cold, or if it is not winter, these formulas must not be used.
The Yangming channel belongs to the Stomach. It cannot be cured without purgation (unblocking and draining); thus, Dahuang (Rhubarb Root) and Mangxiao (Mirabilite) must be used to unblock and drain Yang-Heat. This refers to a situation where the Exterior syndrome has resolved, and symptoms such as headache and aversion to cold have disappeared. The heat then returns to the root of Yangming, and cold-natured formulas like Chengqi Tang (Gut-Purging Decoction) should be used to drain the heat. If aversion to cold persists, the pathogen is still in the Exterior, and purgation is contraindicated. This principle applies even in winter; one must not rigidly adhere to taboos.
The Shaoyang channel belongs to the Gallbladder. It lacks a fixed pathway for entry and exit. Chaihu (Bupleurum Root) and Banxia (Pinellia Tuber) can promote free flow and induce sweating, resolving blood-heat, assisted by Huangqin (Scutellaria Root).
Taiyin Spleen Earth dislikes cold-dampness; only Ganjiang (Dried Ginger) and Baizhu (Atractylodes Rhizome) can dry dampness.
Shaoyin Kidney Water dislikes cold and dryness; only Fuzi (Prepared Aconite Lateral Root) can moisten and warm.
Jueyin Liver Wood stores Blood and nourishes sinews; only Shaoyao (Peony Root) and Gancao (Licorice Root) can nourish. These are the constant principles of medication.
Medicines for releasing the Exterior and attacking the Interior in the treatment of Cold Damage (Shanghan) follow distinct paths of cold and heat. A slight error in their use can lead to death or life instantly. Therefore, Yue Ren (Bian Que) and Zhang Zhongjing paid deep attention to this matter. The *Nan Jing* states: "In Cold Damage with deficient Yang and excessive Yin, sweating leads to recovery, while purgation leads to death. In cases with excessive Yang and deficient Yin, sweating leads to death, while purgation leads to recovery." Furthermore, the invasion of Cold pathogens varies in depth. For shallow invasions, sweating is indicated; for deep invasions, purgation is indicated. This is an unchanging law of ancient and modern times. When Wind-Cold first lodges between the skin and hair, Yin Qi becomes excessive, closing the Cou Li (pores/skin texture). The body's Yang Qi is already deficient and unable to defend against external pathogens, leading to symptoms of aversion to wind and cold. At this time, only acrid-sweet-warm medicines like Guizhi Tang (Cinnamon Twig Decoction) should be used to assist Yang, suppress Yin, and induce sweating. Once the Yin pathogen is dispersed, the Exterior Qi becomes harmonious and the patient recovers. As the Classics state, "Acrid and sweet substances that disperse belong to Yang." If one fails to use this method and instead uses bitter-cold purgatives like Chengqi Tang (Gut-Purcing Decoction), both the Exterior and Interior will be damaged. How could survival be expected? Once the Exterior pathogen is resolved, Cold transforms into Heat. Yang Qi sinks deeply and becomes excessive in the Interior, consuming Body Fluids. The intestines and stomach become dry and obstructed, depleting the True Yin of the Zang-Fu organs. With deficient Yin, symptoms such as delirium, mania, restlessness, thirst, and aversion to heat arise. At this time, bitter-cold agents like Chengqi Tang (Gut-Purging Decoction) should be used to support Yin, suppress Yang, and drain Heat. As the Yang pathogen retreats, the True Yin in the Stomach recovers, the Interior Qi becomes peaceful, and the patient heals. As the *Nei Jing* states, "Sour and bitter substances that induce vomiting and purging belong to Yin." If one fails to use this method and instead uses acrid-hot medicines like Guizhi Tang (Cinnamon Twig Decoction) to aid the pathogen and attack healthy Qi, how could death not occur? Thus, Zhang Zhongjing said: "If Guizhi Tang enters the throat when Yang is excessive, death ensues; if Chengqi Tang enters the stomach when Yin is excessive, death ensues." This is indeed the reason. Alas, is this discourse truly the pivot of sweating and purging methods in Cold Damage? Ordinary physicians fail to grasp its subtleties, ignorant of the principles of Yin-Yang deficiency and excess. To violate this logic without causing death is rare. The Classics say, "To release the Exterior, do not avoid heat; to attack the Interior, do not avoid cold." Is this merely empty talk!