表有邪则为阳虚，温之所以助阳也，阳有所助，则阴邪由以自消，发表之药用温者此也，即经曰阳
虚阴盛，汗之则愈是也。邪传里则化热伤阴，寒之所以抑阳也，阳受其抑，则真阴得以自长，攻里之
药用寒者此也。故经曰阴虚阳盛，下之则愈是也。若阴经自受寒邪，则阳不足而阴有余，故用辛热
以助阳抑阴，此温里之药用热者是也。
传足不传手论
谓伤寒伤足不伤手，可也，谓伤寒传足不传手，则不可也。盖手之六经，皆属金火，故金火不畏寒者
也。其足之六经，曰土、曰木、曰水，以水遇寒则冻冰，木遇寒则叶落，土遇寒则裂不坚，是不能胜其寒
也，故能伤之。由是观之，岂非伤足不伤手者乎。传之一字，必是书写之误，有感而云。
仲景伤寒正名十六种，其余发狂、谵语、郑声、结胸、痞满等症，皆系十六种正病传变所致，岂可概论作伤寒
称之。
伤寒者，冬时冒寒邪，而病即发者也。其症头项痛，腰脊强，发热恶寒，不烦躁，无汗，脉来浮紧而涩，
若在冬时霜降后及春分前，宜用麻黄汤。
伤风者，感冒风邪也。其症头痛、身热、恶风、自汗，脉来浮缓，宜桂枝汤。脉紧而涩，无汗恶寒者，伤寒也，
紧为恶寒，涩为无汗。然寒伤营属阴，阴主必藏，是以无汗，故用麻黄轻扬以发表。浮缓恶风者，伤风
也，浮为伤风，缓为自汗，故用桂枝甘温以解肌。
体表有邪气侵袭，就会导致阳气虚弱，使用温性药物正是为了辅助阳气。既然阳气得到了辅助，阴寒邪气自然就会消除，这就是发表药（用于解除表邪的药物）多用温性的原因所在。正如经典所说：“阳气虚弱、阴寒内盛，通过发汗的方法即可痊愈。”
邪气传入体内后，会化热并损伤阴液，使用寒性药物正是为了抑制亢盛的阳热。既然阳热受到抑制，真阴得以自行生长恢复，这就是攻里药（用于清除里实热结的药物）多用寒性的原因所在。因此经典说：“阴液亏虚、阳热亢盛，通过泻下的方法即可痊愈。”
如果是阴经直接感受寒邪，则会导致阳气不足而阴气有余，所以应当使用辛热性质的药物来辅助阳气、抑制阴寒，这就是温里药（用于温暖脏腑经络的药物）多用热性的原因。
关于“伤寒只传足经不传手经”的论述：
说伤寒伤及足经而不伤手经，是可以的；但说伤寒只传变于足经而不传变于手经，则是错误的。因为手部的六条经脉，都归属于金和火，所以金和火并不畏惧寒邪。而足部的六条经脉，分别属于土、木、水，水遇到寒邪就会结冰，木遇到寒邪就会落叶，土遇到寒邪就会干裂而不坚固，这些都不能抵御寒邪，所以容易受寒邪伤害。由此看来，难道不是伤足而不伤手吗？至于“传”这个字，必定是书写时的错误，我是有感于此才这样说的。
张仲景将伤寒正名定为十六种，其余如发狂、谵语（神志不清，胡言乱语）、郑声（语言重复，声音低微）、结胸（胸胁部硬满疼痛）、痞满（心下痞塞胀满）等症状，都是这十六种正病传变所导致的，怎么能一概而论地称为伤寒呢？
所谓伤寒，是指在冬季冒犯寒邪，随即发病的疾病。其症状表现为头痛项强、腰脊僵硬、发热恶寒、不烦躁、无汗，脉象浮紧而涩。如果在冬季霜降之后到春分之前这段时间患病，适宜使用麻黄汤。
所谓伤风，是指感冒风邪。其症状表现为头痛、身体发热、怕风、自汗，脉象浮缓，适宜使用桂枝汤。如果脉象紧而涩，无汗且恶寒，这是伤寒的表现，紧脉主恶寒，涩脉主无汗。然而，寒邪伤及营分属阴，阴主闭藏，所以表现为无汗，因此使用麻黄轻扬之性以发散表邪。如果脉象浮缓且怕风，这是伤风的表现，浮脉主伤风，缓脉主自汗，因此使用桂枝甘温之性以解肌祛风。
When pathogenic factors invade the exterior, it results in Yang deficiency. The use of warm-natured drugs is intended to assist Yang. Once Yang is assisted, Yin pathogens will naturally dissipate. This is why releasing-the-exterior drugs are often warm in nature. As stated in the classics: "In cases of Yang deficiency and Yin excess, sweating (diaphoresis) leads to recovery."
When pathogens transmit inward, they transform into heat and damage Yin. The use of cold-natured drugs is intended to suppress excessive Yang. Once Yang is suppressed, True Yin can grow and recover on its own. This is why purgative drugs for clearing interior excesses are often cold in nature. Therefore, the classics state: "In cases of Yin deficiency and Yang excess, purgation (downward draining) leads to recovery."
If the Yin meridians directly contract cold pathogens, Yang becomes insufficient while Yin becomes excessive. Thus, acrid-hot drugs are used to assist Yang and suppress Yin. This explains why warming-the-interior drugs are often hot in nature.
On the Theory that Taiyang Cold Damage Transmits Only to the Foot Meridians and Not the Hand Meridians:
It is acceptable to say that Cold Damage injures the Foot meridians but not the Hand meridians; however, it is incorrect to say that Cold Damage transmits only within the Foot meridians and does not transmit to the Hand meridians. The six Hand meridians all belong to Metal and Fire, so Metal and Fire do not fear cold. The six Foot meridians belong to Earth, Wood, and Water. Water freezes when encountering cold; Wood sheds its leaves when encountering cold; Earth cracks and loses firmness when encountering cold. These cannot withstand the cold, hence they are susceptible to injury. From this perspective, is it not true that the Foot meridians are injured while the Hand meridians are spared? The character "transmit" (chuan) here must be a scribal error; I speak out of reflection on this matter.
Zhang Zhongjing defined sixteen primary types of Cold Damage. Other symptoms such as mania (fa kuang), delirious speech (chan yu), monotonous repetition of words (zheng sheng), chest binding with pain (jie xiong), and epigastric fullness/stuffiness (pi man) are all caused by the transmission and transformation of these sixteen primary diseases. How can they be generally categorized simply as Cold Damage?
Cold Damage refers to illness that manifests immediately after exposure to cold pathogens during winter. Its symptoms include headache and stiffness of the neck and occiput, stiffness of the lower back and spine, fever with aversion to cold, absence of irritability, anhidrosis (lack of sweating), and a pulse that is floating, tight, and choppy. If contracted between the Frost Descent (Shuang Jiang) solar term in winter and the Spring Equinox (Chun Fen), Mahuang Tang (Ephedra Decoction) is appropriate.
Wind Injury refers to contracting wind pathogens. Its symptoms include headache, body heat, aversion to wind, and spontaneous sweating, with a pulse that is floating and moderate (slow/loose). Guizhi Tang (Cinnamon Twig Decoction) is appropriate. If the pulse is tight and choppy, accompanied by anhidrosis and aversion to cold, it is Cold Damage. A tight pulse indicates aversion to cold; a choppy pulse indicates anhidrosis. Since cold injuring the Ying (Nutrient) level belongs to Yin, and Yin governs storage/closure, anhidrosis occurs. Therefore, the light and ascending properties of Ephedrae Herba (Mahuang, 麻黄) are used to release the exterior. If the pulse is floating and moderate with aversion to wind, it is Wind Injury. A floating pulse indicates Wind Injury; a moderate pulse indicates spontaneous sweating. Therefore, the sweet and warm properties of Cinnamomi Ramulus (Guizhi, 桂枝) are used to resolve the muscle layer.