三阳经有阳症，无阴症；三阴经有阴症，有虚症。人多知之。三阴经阳症，则有不知者。仲
景深恐后人惑此，故详注从阳经先发热，后传至三阴者，乃是传经之热病，名曰伤寒，此
即《内经》所谓热病之条；若初起不发热，乃是直中阴经之寒病，名曰阴症。后人因见阴症阳
症同在篇中，认误热病传入三阴亦是阴症；又误认初起虽有热病，今日久手足皆冷，六脉沉
细已变阴病。不知初起发热已是热病根源，或失于散表而表邪内陷，或失于清里而里热内
伏，传入阴经而手足反冷，经虽属阴，症则阳症，此乃是阴经热病，非变阴症。例如太阴病
手足自温，当发身黄者，少阴病但厥无汗，少阴病心中烦不得卧者，少阴病下利咽痛心烦
者，少阴病下利六七日心烦不得眠者，少阴病自利清水心下必痛者，厥阴病下利脉数而渴者，
厥阴下利脉数有微热者，厥阴下利欲饮水者，厥阴呕而发热下利谵语者，凡此乃是阴经之热
病，多用承气汤主治者。夫热既传于阴经，则热深厥亦深，身反无热，脉反沉细。不知手足
厥冷，原能举动，不比阴寒厥冷，手足冷而不得动移者。身虽不热，唇口必干而焦，不比阴
症之口中和而有水者。脉沉细重，按必细而带数，不比阴寒之脉沉细而迟者。更有大分别
者，三阴寒病神志清爽，三阴热病神识昏迷；三阴寒病即口干不能饮水，三阴热病口干必然
消水；三阴寒病二便清利，三阴热病二便赤涩。一阴一阳，天坏各别者也。
三阳经只有阳证，没有阴证；三阴经有阴证，也有虚证。人们大多知道这一点。但关于三阴经的阳证，却有人不了解。张仲景深怕后人对此产生困惑，所以详细注明：凡是先从阳经发热，然后传变至三阴经的，这是传经的热病，名称叫伤寒，这就是《内经》所说的热病的条文；如果初起时不发热，这是寒邪直接中于阴经的寒病，名称叫阴证。后人因为看到阴证和阳证同在一篇中，错误地认为热病传入三阴经也是阴证；又错误地认为初起虽然有热病，但如果日久手足都变冷，六脉沉细，就已经变成了阴病。他们不知道初起发热已经是热病的根源，或者因为未能及时发散表邪导致表邪内陷，或者因为未能及时清解里热导致里热内伏，传入阴经后反而出现手足寒冷。虽然经络属于阴经，但症状表现为阳证，这实际上是阴经的热病，并非转变为阴证。例如太阴病手足自然温暖，应当发生身黄的；少阴病仅有四肢厥冷而无汗出的；少阴病心中烦躁不得卧睡的；少阴病下利、咽痛、心烦的；少阴病下利六七日后心烦不得眠的；少阴病自利清水且心下必定疼痛的；厥阴病下利脉数且口渴的；厥阴病下利脉数且有轻微发热的；厥阴病下利想喝水的；厥阴病呕吐且发热、下利、谵语的，凡这些情况都是阴经的热病，多用承气汤来主治。既然热邪已经传入阴经，那么热越深厥逆就越深，身体反而不热，脉象反而沉细。但他们不知道手足厥冷，原本还能活动，并不像阴寒厥冷那样，手足冰冷而不能移动。身体虽然不热，嘴唇和口腔必然干燥焦枯，并不像阴证那样口中平和而有津液。脉象沉细重按，必然细而带数，并不像阴寒之脉沉细而迟滞。更有重大区别的是：三阴寒病神志清爽，三阴热病神识昏迷；三阴寒病即使口干也不能饮水，三阴热病口干必然要喝水；三阴寒病二便清长通利，三阴热病二便赤黄涩痛。一阴一阳，天地性质各自不同啊。
The Three Yang meridians have only Yang patterns and no Yin patterns; the Three Yin meridians have Yin patterns and also deficiency patterns. Most people are aware of this. However, regarding Yang patterns in the Three Yin meridians, there are those who do not understand. Zhang Zhongjing deeply feared that future generations would be confused by this, so he detailed notes stating: Those who first experience fever in the Yang meridians and then transmit to the Three Yin meridians are suffering from a heat disease transmitted via meridians, named Shanghan (Cold Damage), which corresponds to the clauses on heat diseases mentioned in the *Neijing* (Inner Canon); if there is no fever at the onset, it is a cold disease where pathogenic cold directly strikes the Yin meridians, named Yin pattern. Later practitioners, seeing both Yin and Yang patterns in the same chapter, mistakenly believed that heat diseases transmitting to the Three Yin meridians are also Yin patterns; they further mistakenly believed that although there was a heat disease at the onset, if after a long time the hands and feet become cold and the six pulses are deep and fine, it has already transformed into a Yin disease. They did not realize that the initial fever is already the root of the heat disease; whether due to failure to dissipate the exterior pathogen leading to its internal collapse, or failure to clear the interior heat leading to its internal retention, upon transmitting to the Yin meridians, the hands and feet may paradoxically become cold. Although the meridians belong to Yin, the symptoms manifest as Yang patterns; this is actually a heat disease of the Yin meridians, not a transformation into a Yin pattern. For example, in Taiyin disease where the hands and feet are naturally warm, jaundice should develop; in Shaoyin disease with only cold extremities and no sweat; in Shaoyin disease with vexation in the heart and inability to lie down; in Shaoyin disease with diarrhea, sore throat, and vexation; in Shaoyin disease with diarrhea for six or seven days, vexation, and inability to sleep; in Shaoyin disease with spontaneous purging of clear water and必 (must) pain in the epigastrium; in Jueyin disease with diarrhea, rapid pulse, and thirst; in Jueyin disease with diarrhea, rapid pulse, and slight fever; in Jueyin disease with diarrhea and desire to drink water; in Jueyin disease with vomiting, fever, diarrhea, and delirious speech—all these are heat diseases of the Yin meridians, mostly treated with Chengqi Tang (Gut-Draining Decoction). Since the heat has transmitted to the Yin meridians, the deeper the heat, the deeper the cold extremities (Jue); the body may paradoxically feel no heat, and the pulse may paradoxically be deep and fine. But one must not forget that in cold extremities due to heat, the hands and feet can originally move, unlike cold extremities due to Yin-cold, where the hands and feet are cold and immobile. Although the body is not hot, the lips and mouth will inevitably be dry and scorched, unlike Yin patterns where the mouth is neutral and moist. The pulse is deep and fine; upon heavy pressure, it must be fine and rapid, unlike Yin-cold patterns where the pulse is deep, fine, and slow. There is an even greater distinction: In Three Yin cold diseases, the spirit and consciousness are clear; in Three Yin heat diseases, the spirit and consciousness are confused or comatose; in Three Yin cold diseases, even if the mouth is dry, drinking is impossible; in Three Yin heat diseases, if the mouth is dry, drinking is inevitable; in Three Yin cold diseases, urination and defecation are clear and free-flowing; in Three Yin heat diseases, urination and defecation are red, scanty, and difficult. One Yin and one Yang, their natures are as different as Heaven and Earth.