夫脉浮当汗，脉沉当下，固其宜也。其脉虽浮亦有可下者，谓邪热入腑，大便难也。大便不难，
岂敢下乎？其脉虽沉亦有可汗者，谓少阴病，身有热也。假若身不发热，岂敢汗乎？此取证不取脉
也。
盖风则伤卫气，寒则伤荣血者，缘气本属阳，风属阳，阳则从阳，故伤卫气。阳主开泄，皆令
自汗，故用桂枝汤辛甘温之剂以实表。血本属阴，寒属阴，阴则从阴，故伤荣血。阴主闭藏，皆令
无汗，故用麻黄汤轻扬之剂以发表。正所谓水流湿而火就燥，云从龙而风从虎，各从其类者是也。
夫发表之药用温，攻里之药用寒，温里之药用热者，表既有邪，则为阳虚阴盛，
温之，乃所以为阳，阳有所助而长，则阴邪所由以消，故用辛甘温之剂。发散为阳，此指发表之药
用温者明矣。里既有邪，则为阴虚阳盛，寒之，乃所以助阴而抑阳，阳受其抑则微，而真阴所由以
长，故用酸苦之剂。泻涌为阴，此指攻里之药用寒者明矣。阴经自受寒邪，则为脏病，主阳不足而
阴有余，故用辛热之剂以助阳抑阴，此指温经之药用热者明矣。表有邪不汗之，其邪何从而去？里
有邪不下之，其邪何从而出？脏有寒不温之，其寒何从而除？此三者，所谓用药寒温辩也。
夫伤寒二字，盖冬时天气严寒，以水冰地冻而成杀厉之气，人触犯之，实时病者，为正伤寒，
乃有恶寒，头疼发热之证，故用麻黄、桂枝发散表中寒邪，自然热退身凉，有何变证？如或头疼恶
寒表证皆除，而反见谵语怕热，燥渴大便闭者，以法下之，大便通而热愈，有何怪证？其余春、夏、
秋三时，虽有恶寒身热，头疼，亦微，即为感冒非时暴寒之轻，非比冬时气正伤寒为重也。如冬感
寒不即病，伏藏于肌肤，至春夏时，其伏寒各随时气改变为温，为热者，因温暑将发，又受暴寒，
故春变为温病。既变之后，不得复言其为寒矣。所以仲景有云发热，不恶寒而渴者，其理可见温病
也。暑病亦然，比之温病，尤加热也。不恶寒则病非外来，渴则明其热自内达表，无表证明矣。治
温暑大抵不宜发汗，过时而发不在表也。其伏寒至夏，又感暴寒，变为暑病。暑病者，即热病也，取
夏火当权而言暑字。缘其温暑二证，从冬时伏寒所化，总曰伤寒，所发之时既异，治之不可混也。
若言四时俱是正伤寒者，非也。此三者，皆用辛凉之剂以解之。若将冬时正伤寒之药通治之，定杀人
矣。辛凉者，羌活冲和汤是也。兼能代大青龙汤，治伤寒见风，伤风见寒，为至稳。一方可代三方，
危险之药如坦夷，其神乎哉！世俗皆所未知也。若表解而里证具者，亦以法下之无惑。又伤寒汗下
后过经不愈者，亦温病也。已经汗下，亦不在表也，随病制宜。凡有辛苦劳役之人，有患头疼，恶
寒身热，加之骨腿酸疼，微渴自汗，脉虽浮大而无力，此为劳力感寒，用补中益气兼辛温之剂为良。
经云温能除大热，正此谓也。若当和解者，即以小柴胡加减和之。下证见者，即以本方加大黄微利
之，切勿过用猛烈，其害非细。若初病无身热，无头疼，便就怕寒厥冷，腹痛，呕吐泄泻，脉来沉
迟无力，此为直中寒证，宜温之而不宜汗下也。疫疠者，皆时行不正之
气，老幼传染相同者是也。缘人不近秽气，免伤真气。若近秽气，有伤真气，故病相传染。正如墙
壁固，贼人不敢入，正气盛，邪气不敢侵。正气既虚，邪得乘机而入，与前温暑治又不同。表证见
者，人参败毒散。半表半里证者，小柴胡。里证具者，大柴胡下之。无以脉诊，以平为期。与其疟
痢等证，亦时疫也，照常法例治之。
脉象浮通常应当使用发汗法，脉象沉通常应当使用攻下法，这本来是适宜的。但是脉象虽然浮也有可以使用攻下法的，这是因为邪热进入腑中，导致大便困难。如果大便不困难，怎么敢使用攻下法呢？脉象虽然沉也有可以使用发汗法的，这是指少阴病，身体有发热症状。假如身体不发热，怎么敢使用发汗法呢？这是依据症状而不单纯依据脉象来判断。
大凡风邪伤害卫气，寒邪伤害营血，这是因为气本属阳，风也属阳，阳类相从，所以伤害卫气。阳主开泄，会导致自汗，所以用桂枝汤（Cinnamon Twig Decoction）这种辛甘温的方剂来充实表气。血本属阴，寒也属阴，阴类相从，所以伤害营血。阴主闭藏，会导致无汗，所以用麻黄汤（Ephedra Decoction）这种轻扬升散的方剂来发散表邪。这正是所谓“水流湿而火就燥，云从龙而风从虎”，各从其类的道理。
凡是发散表邪的药物多用温性，攻逐里实的药物多用寒性，温补里的药物多用热性。因为表有邪气，就是阳气虚弱阴气盛，用温药，是为了扶助阳气，阳气得到帮助而增长，阴邪因此得以消除，所以用辛甘温的方剂。发散属于阳，这里指明发散表邪的药物用温性是显而易见的。里有邪气，就是阴气虚弱阳气盛，用寒药，是为了辅助阴气而抑制阳气，阳气受到抑制则微弱，真阴因此得以生长，所以用酸苦味的方剂。泻下涌吐属于阴，这里指明攻逐里实的药物用寒性是显而易见的。阴经直接感受寒邪，就成为脏病，主要表现是阳气不足而阴气有余，所以用辛热的方剂来助阳抑阴，这里指明温经的药物用热性是显而易见的。表有邪气如果不发汗，邪气从哪里去除？里有邪气如果不攻下，邪气从哪里排出？脏有寒邪如果不温补，寒邪从哪里消除？这三者，就是所说的用药寒温的辨别。
“伤寒”这两个字，大概是指冬季天气严寒，因水结冰地冻结而形成杀厉之气，人触犯它，随即发病的，称为正伤寒（True Cold Damage），表现为恶寒、头痛、发热等症状，所以用麻黄（Ephedrae Herba）、桂枝（Cinnamomi Ramulus）发散表中的寒邪，自然热退身凉，有什么变证呢？如果头疼恶寒等表证都消除了，反而出现谵语、怕热、烦躁口渴、大便闭塞的症状，按照方法使用攻下法，大便通畅后热势更退，有什么奇怪的证候呢？其余春、夏、秋三个季节，虽然有恶寒身热、头痛，但都很轻微，这就是感冒非时暴寒（Casual Cold Exposure），病情较轻，不像冬季的正伤寒那样严重。如果在冬季感受寒邪没有立即发病，潜伏藏在肌肤之间，到了春夏季节，潜伏的寒邪随着当时的气候改变转化为温病或热病，因为温暑之气将要发作，又受到暴寒侵袭，所以在春季变为温病。既然已经转化，就不能再说它是寒邪了。所以张仲景说：“发热，不恶寒而口渴的”，其道理可见是温病。暑病也是这样，比温病更加热盛。不恶寒说明病非外来，口渴说明热由内达表，没有表证是很明显的。治疗温病和暑病大体上不宜发汗，因为过时发作的病不在表。潜伏的寒邪到了夏季，又感受暴寒，变为暑病。暑病，就是热病，取夏季火气当权而言“暑”字。因为温病和暑病这两种证候，都是由冬季潜伏的寒邪所化生，总称为伤寒，但发作的时间既已不同，治疗不可混淆。如果说四季都是正伤寒，是不对的。这三种情况（温、暑、伏寒化热），都用辛凉的方剂来解之。如果用冬季正伤寒的药物通用治疗，一定会致人死亡。辛凉的方剂，如羌活冲和汤（Qianghuo Chonghe Decoction），兼能代替大青龙汤（Major Green Dragon Decoction），治疗伤寒见风、伤风见寒，最为稳妥。一方可以代替三方，将危险的药物变得像平地一样安全，真是神奇啊！世俗之人都不知道这些。如果表证解除而里证具备的，也依法使用攻下法，不要疑惑。另外，伤寒经过汗法、下法治疗后，超过病程阶段仍未痊愈的，也是温病。既然已经经过汗下，病就不在表了，应根据病情灵活制宜。凡是从事辛苦劳役的人，患上头痛、恶寒、身热，加上骨腿酸痛、微渴、自汗，脉象虽然浮大但无力，这是劳力感寒（Cold Injury due to Labor），用补中益气汤（Buzhong Yiqi Decoction）兼用辛温的方剂为良。经文说“温能除大热”，正是说的这个意思。如果应当和解的，就用小柴胡汤（Minor Chaihu Decoction）加减来和解。出现攻下证的，就用本方加大黄（Rhei Radix et Rhizoma）轻微通利，切勿过度使用猛烈药物，其危害不小。如果初起没有身热、没有头痛，就怕冷厥冷、腹痛、呕吐泄泻，脉象沉迟无力，这是直中寒证（Direct Invasion of Cold Syndrome），宜用温法而不宜用汗法和下法。疫疠（Plague/Epidemic Disease），都是时行不正之气，老少传染症状相同的就是。因为人不接近秽浊之气，就能避免损伤真气。如果接近秽浊之气，就会损伤真气，所以疾病相互传染。正如墙壁坚固，贼人不敢进入；正气旺盛，邪气不敢侵犯。正气既然虚弱，邪气就趁机而入，这与前面温病、暑病的治疗方法又不同。出现表证的，用人参败毒散（Ginseng Decoction for Overcoming Toxins）。半表半里证的，用小柴胡汤。里证具备的，用大柴胡汤（Major Chaihu Decoction）攻下。如果没有脉诊条件，以平复为标准。至于疟疾、痢疾等证候，也属于时疫，照常法例治疗即可。
Pulse floating generally indicates the need for sweating therapy, and pulse sinking generally indicates the need for purgation; this is indeed appropriate. However, even if the pulse is floating, there are cases where purgation may be used; this refers to pathogenic heat entering the Fu organs, causing difficulty in defecation. If defecation is not difficult, how could one dare to use purgation? Even if the pulse is sinking, there are cases where sweating therapy may be used; this refers to Shaoyin disease (Disease of the Lesser Yin) presenting with fever in the body. If there were no fever, how could one dare to use sweating therapy? This approach prioritizes symptoms over pulse diagnosis.
Generally, wind pathogens damage Wei Qi (Defensive Qi), while cold pathogens damage Ying Blood (Nutritive Blood). This is because Qi belongs to Yang, and wind also belongs to Yang; like attracts like, so it damages Wei Qi. Yang governs opening and dispersing, leading to spontaneous sweating; therefore, Guizhi Tang (Cinnamon Twig Decoction), a pungent-sweet-warm formula, is used to strengthen the exterior. Blood belongs to Yin, and cold also belongs to Yin; like attracts like, so it damages Ying Blood. Yin governs closure and storage, leading to an absence of sweat; therefore, Mahuang Tang (Ephedra Decoction), a light and ascending formula, is used to release the exterior. This is precisely what is meant by "water flows to wetness, fire moves toward dryness; clouds follow dragons, wind follows tigers"—each following its own kind.
Medicines used to release the exterior are typically warm; medicines used to purge the interior are typically cold; medicines used to warm the interior are typically hot. When pathogens are on the exterior, it signifies deficiency of Yang and excess of Yin. Using warm medicines aids Yang; as Yang grows with assistance, the Yin pathogen is thereby eliminated. Hence, pungent-sweet-warm formulas are used. Dispersal is Yang; thus, it is clear that exterior-releasing medicines should be warm. When pathogens are in the interior, it signifies deficiency of Yin and excess of Yang. Using cold medicines assists Yin and suppresses Yang; as Yang is suppressed and becomes weak, True Yin is thereby nourished. Hence, sour-bitter formulas are used. Purging and vomiting are Yin; thus, it is clear that interior-purging medicines should be cold. When the Yin meridians directly contract cold pathogens, it results in Zang organ disease, characterized primarily by insufficient Yang and excess Yin. Therefore, pungent-hot medicines are used to assist Yang and suppress Yin; thus, it is clear that meridian-warming medicines should be hot. If pathogens on the exterior are not released via sweating, from where will they depart? If pathogens in the interior are not expelled via purgation, from where will they exit? If cold in the Zang organs is not warmed, from where will it be removed? These three aspects constitute the distinction in using cold, warm, and hot medicines.
The term "Shanghan" (Cold Damage) generally refers to the severe cold weather in winter, which creates a lethal qi due to frozen water and ice. When humans encounter this and fall ill immediately, it is called Zheng Shanghan (True Cold Damage), presenting with aversion to cold, headache, and fever. Therefore, Mahuang (Ephedrae Herba) and Guizhi (Cinnamomi Ramulus) are used to disperse cold pathogens from the exterior and interior, naturally resulting in the subsidence of fever and cooling of the body. What complications would arise? If the exterior symptoms such as headache and aversion to cold are resolved, but instead delirium, fear of heat, irritability, thirst, and constipation appear, purgation should be applied according to the method. Once defecation is achieved and heat further subsides, what strange symptoms remain? In spring, summer, and autumn, although there may be mild aversion to cold, fever, and headache, these are merely Gaomao Bishi Baohan (Casual Cold Exposure due to Non-seasonal Cold), which are mild compared to the severity of True Cold Damage in winter. If cold is contracted in winter but does not manifest immediately, it lies latent in the skin and muscles. By spring or summer, this latent cold transforms into Warm Disease (Wenbing) or Heat Disease according to the seasonal qi. Because Warmth and Summerheat are about to emerge, and sudden cold is encountered, spring changes become Warm Disease. Once transformed, it can no longer be referred to as cold. Thus, Zhang Zhongjing stated: "Fever without aversion to cold and with thirst" indicates Warm Disease. Summerheat disease is similar but more intense than Warm Disease. Lack of aversion to cold indicates the pathogen is not external; thirst indicates heat radiating from within to the exterior, confirming the absence of exterior syndrome. Treatment for Warm and Summerheat diseases generally avoids sweating, as diseases occurring after the season are no longer on the exterior. Latent cold reaching summer, combined with sudden cold exposure, transforms into Summerheat disease. Summerheat disease is essentially Heat Disease; the term "Summerheat" is derived from the dominance of Fire in summer. Since both Warm and Summerheat conditions originate from latent winter cold and are collectively termed Cold Damage, their different timing of onset necessitates distinct treatments. It is incorrect to claim that all seasons involve True Cold Damage. For these three types (Warm, Summerheat, and latent cold transformation), acrid-cool formulas should be used. Using winter True Cold Damage medicines universally would certainly cause death. Acrid-cool formulas, such as Qianghuo Chonghe Tang (Qianghuo Harmonizing Decoction), can substitute for Da Qinglong Tang (Major Green Dragon Decoction), treating Cold Damage complicated by wind or Wind Strike complicated by cold, providing utmost stability. One formula substitutes for three, turning dangerous drugs into safe ones, which is truly miraculous! The common people are unaware of this. If the exterior is resolved but interior symptoms prevail, purgation should be applied without hesitation. Furthermore, if Cold Damage persists beyond the usual course despite sweating and purgation, it is also considered Warm Disease. Having undergone sweating and purgation, the pathogen is no longer on the exterior; treatment must adapt to the specific condition. For individuals engaged in hard labor who suffer from headache, aversion to cold, fever, soreness of bones and legs, slight thirst, spontaneous sweating, and a floating but large and forceless pulse, this is Cold Injury due to Labor (Laoli Ganhan). Bu Zhong Yi Qi Tang (Tonify the Middle and Augment the Qi Decoction) combined with acrid-warm medicines is beneficial. The classic states, "Warmth can eliminate great heat," referring precisely to this. If harmonization is indicated, Xiao Chaihu Tang (Minor Chaihu Decoction) with modifications should be used. If purgation indications appear, add Rhei Radix et Rhizoma (Rhubarb) to the base formula for mild purgation; do not overuse harsh medicines, as the harm would be significant. If the initial illness presents without fever or headache, but with aversion to cold, cold limbs, abdominal pain, vomiting, diarrhea, and a deep, slow, and forceless pulse, this is Direct Invasion of Cold Syndrome (Zhizhong Hanzheng). It requires warming and prohibits sweating and purgation. Epidemic Plagues (Yili) are caused by abnormal seasonal qi, spreading identically among old and young. Avoiding foul odors prevents damage to True Qi. Proximity to foul odors damages True Qi, leading to contagion. Just as a solid wall prevents thieves from entering, robust Righteous Qi prevents Pathogenic Qi from invading. When Righteous Qi is deficient, Pathogenic Qi takes advantage. This differs from the treatment of Warm and Summerheat diseases. For exterior syndromes, Ren Shen Bai Du San (Ginseng Decoction for Overcoming Toxins) is used. For half-exterior/half-interior syndromes, Xiao Chaihu Tang is used. For full interior syndromes, Da Chaihu Tang (Major Chaihu Decoction) is used for purgation. Without pulse diagnosis, aim for equilibrium. Conditions such as malaria and dysentery are also epidemic diseases and should be treated according to standard methods.