难经曰。伤寒阳虚阴盛。汗出而愈。下之即死。阳盛阴虚。汗出而死。下之而愈。嗟乎。其伤
寒汗下之枢机乎。夫邪之伤于人也。有浅深焉。浅则居表。深则入里。居表则闭腠理。发
怫热。见恶寒。恶风。头痛等证。于斯时也。惟辛温解散。而可愈。入里则为燥屎。作潮热
。形狂言。谵语。大渴等证。于斯时也。惟咸寒攻下而可平。夫寒邪外客。非阴盛而阳虚
乎
。热邪内炽。非阳盛而阴虚乎。汗下一瘥。生死反掌。吁。是言也。谓之伤寒汗下枢机。其
不然欤。惜乎释者旁求。厥义滋隐。外台秘要曰。此阴阳指身之表里言。病者为虚。不病者
为盛。表病里和。是阳虚阴盛也。表和里病。是阳盛阴虚也。窃意阴阳之在人。均则宁。
偏则病。无过不及之谓均。过与不及之谓偏。盛则过矣。虚则不及矣。其可以盛为和乎。故
内经云。邪气盛则实。精气夺则虚。且谓阳虚当汗。阴虚当下。乃遗邪气。而反指正气为言
。得无晦乎。伤寒微旨曰。此阴阳指脉之尺寸言。尺脉实大。寸脉短小。名阴盛阳虚。可汗
。寸脉实大。尺脉短小。名阳盛阴虚。可下。苟汗证已具。而脉未应。必待尺脉力过于寸而
后行。下证已具。而脉未应。必待寸脉力过于尺而后用。窃意越人设难。以病不以脉。其所
答也。何反以脉。不以病乎。且脉固以候病也。倘汗下之证已急。不可稍缓。待脉应而未应
。欲不待。则惑于心。欲待之。则虑其变。二者之间。将从病欤。将从脉欤。吾不得无疑于
此也。或诘予曰。仲景伤寒论引此。而继以桂枝下咽。阳盛则毙。矛气入胃。阴盛以亡之语
。夫桂枝表药。承气里药。反则为害。是固然矣。然麻黄汤亦表药也。其不言之何欤。且子
以阴盛为寒邪。寒邪固宜用麻黄也。今反举桂枝。又何欤。予曰。何不味仲景之言乎。其曰
凡伤寒之病。多从风寒得之。又曰脉浮而紧。浮则为风。紧则为寒。又桂枝汤条。而曰啬啬
恶寒。淅淅恶风。麻黄汤条。而曰恶风。夫风寒分言。则风阳而寒阴。风苟行于天地严凝凛
洌
之时。其得谓之阳乎。是则风寒常相因耳。故桂枝麻黄皆温剂也。以温剂为治。足以见风寒
之俱为阴邪矣。但伤卫则桂枝。伤荣则麻黄。荣卫虽殊。其为表则一耳。仲景此言。但以戒
汗下之误为主。不为荣卫设也。举桂枝则麻黄在其中矣。所谓阳盛即毙者。是言表证已罢。
而里证既全。可攻而不可汗。所谓阴盛以亡者。是言里证未形。而表证独具。可汗而不可攻
。由是观之。则越人仲景之本旨。庶乎畅然于其中矣。
《难经》说：伤寒病中，阳虚阴盛，应当发汗，汗出则痊愈；若误用攻下法，就会导致死亡。阳盛阴虚，应当攻下，攻下则痊愈；若误用发汗法，就会导致死亡。唉！这真是掌握了伤寒病使用汗法和下法的关键啊。
邪气侵犯人体，有浅层和深层的区别。浅层的邪气停留在体表，深层的邪气进入体内。邪气在体表，就会闭塞腠理（皮肤毛孔及其间隙），导致郁热不得发散，出现怕冷、怕风、头痛等症状。在这个时候，只有用辛温解表的方法发散邪气，才能痊愈。邪气进入体内，就会形成燥结的大便，引起潮热（定时发热）、神志狂乱、胡言乱语、极度口渴等症状。在这个时候，只有用咸寒性质的药物攻下里实，才能平复病情。
外来的寒邪侵袭，难道不是阴盛而阳虚吗？体内的热邪炽盛，难道不是阳盛而阴虚吗？发汗或攻下一次，病情就能好转，生死往往就在反掌之间。唉！这句话，说是掌握伤寒病汗下法的枢机关键，难道不对吗？可惜那些解释的人旁征博引，使得其中的真意更加隐晦不明。
《外台秘要》说：这里的阴阳是指身体的表里而言。生病的部位就是“虚”，没生病的部位就是“盛”。表有病而里气和，这叫阳虚阴盛；表和而里有病，这叫阳盛阴虚。我私下认为，阴阳在人身上，平衡就安宁，偏颇就生病。“无过不及”叫做平衡，“过”与“不及”叫做偏颇。所谓“盛”就是太过，“虚”就是不足。怎么可以把“盛”理解为“和”呢？所以《内经》说：“邪气盛则实，精气夺则虚。”况且如果说阳虚当发汗、阴虚当攻下，这是忽略了邪气的存在，反而去指正气来说事，岂不是让人困惑吗？
《伤寒微旨》说：这里的阴阳是指脉象的寸口和尺部而言。尺脉实大，寸脉短小，名叫阴盛阳虚，可以发汗；寸脉实大，尺脉短小，名叫阳盛阴虚，可以攻下。如果发汗的证候已经具备，但脉象没有相应表现，必须等到尺脉的力量超过寸脉之后才施行发汗法；如果攻下的证候已经具备，但脉象没有相应表现，必须等到寸脉的力量超过尺脉之后才使用攻下法。我私下认为，扁鹊（越人）提出这个难题，是以病症为依据而不是以脉象为依据，那么他的回答为什么反而以脉象为依据，不以病症为依据呢？而且脉象固然用来诊察疾病，但如果汗下证的病情已经紧急，不能稍微延缓。等待脉象应而未应，心里想不等待，就会感到困惑；心里想等待，又担心病情发生变化。在这两者之间，是顺从病症呢，还是顺从脉象呢？我对这一点不能不产生怀疑。
有人责问我道：张仲景的《伤寒论》引用了这段话，接着又说“桂枝汤服下，阳盛就会毙命；承气汤入胃，阴盛就会死亡”。桂枝汤是解表的药，承气汤是治里的药，如果用反了就会造成危害，这确实是这样的。但是麻黄汤也是解表的药，为什么仲景没有提到它呢？况且您把阴盛理解为寒邪，寒邪本来适宜用麻黄汤治疗，现在却举出桂枝汤，又是为什么呢？
我回答说：为什么不仔细体味张仲景的话呢？他说：“凡是伤寒的病，大多从风寒得来。”又说：“脉浮而紧，浮脉代表风，紧脉代表寒。”在桂枝汤条文中，提到“啬啬恶寒，淅淅恶风”；在麻黄汤条文中，提到“恶风”。如果把风和寒分开来说，风属阳，寒属阴。但是，如果风在天地严寒凛冽的时候运行，它能被称为阳吗？这说明风和寒常常是相伴而来的。所以桂枝汤和麻黄汤都是温性的方剂。用温性方剂来治疗，足以说明风和寒都属于阴邪。只是伤及卫气就用桂枝汤，伤及营血就用麻黄汤。营气和卫气虽然不同，但它们都在体表，这一点是一样的。张仲景这句话，主要是为了告诫不要误用汗法和下法，并不是专门为了区分营卫而设立的。举出桂枝汤，就意味着麻黄汤也在其中了。所说的“阳盛即毙”，是说表证已经解除，而里证已经完全形成，可以攻下而不宜发汗；所说的“阴盛以亡”，是说里证还没有显现，而表证单独存在，可以发汗而不宜攻下。由此看来，扁鹊和张仲景的本意，大概就能在其中畅然明白了。
The *Nan Jing* (Classic of Difficult Issues) states: In typhoid fever, if there is deficiency of Yang and excess of Yin, sweating should be induced; when sweat is released, the patient recovers. If purgation is used mistakenly, death ensues. If there is excess of Yang and deficiency of Yin, purgation should be used; when purgation is applied, the patient recovers. If sweating is used mistakenly, death ensues. Alas! This truly grasps the pivotal mechanism for using sweating and purgation methods in typhoid fever.
Pathogenic factors invading the human body have depths of penetration. Shallow pathogens reside at the exterior, while deep pathogens enter the interior. When pathogens reside at the exterior, they close the *Cou Li* (pores and interstices of the skin), causing stifled heat to accumulate, manifesting as aversion to cold, aversion to wind, headache, and other syndromes. At this time, only dispersing with acrid-warm herbs can lead to recovery. When pathogens enter the interior, they form dry fecal impaction, causing tidal fever, manic behavior, delirious speech, extreme thirst, and other syndromes. At this time, only attacking the interior with salty-cold herbs can pacify the condition.
External cold pathogens invading do not constitute an excess of Yin and deficiency of Yang? Internal hot pathogens blazing do not constitute an excess of Yang and deficiency of Yin? A single instance of sweating or purgation can bring relief; life and death can reverse in the turn of a palm. Alas! To call this statement the pivotal mechanism for sweating and purgation in typhoid fever—is it not correct? It is lamentable that commentators seek explanations elsewhere, making its meaning even more obscure.
The *Waitai Miyao* (Secret Essentials of the Outer Cabinet) states: Here, Yin and Yang refer to the exterior and interior of the body. The diseased area is "deficient," and the healthy area is "excessive." Exterior disease with interior harmony is called deficiency of Yang and excess of Yin; exterior harmony with interior disease is called excess of Yang and deficiency of Yin. I privately believe that within a person, Yin and Yang must be balanced for peace; imbalance leads to disease. "Neither excessive nor insufficient" is called balance; "excessive or insufficient" is called imbalance. "Excess" implies going beyond limits, while "deficiency" implies falling short. How can one consider "excess" as "harmony"? Therefore, the *Nei Jing* (Inner Canon) states: "When pathogenic Qi is excessive, it is Excess syndrome; when Essence and Qi are depleted, it is Deficiency syndrome." Furthermore, saying that Yang deficiency warrants sweating and Yin deficiency warrants purgation ignores the pathogenic factor and instead refers to the Healthy Qi, which is confusing.
The *Shanghan Weizhi* (Subtle Principles of Typhoid Fever) states: Here, Yin and Yang refer to the Cun (inch) and Chi (cubit) positions of the pulse. If the Chi pulse is solid and large, and the Cun pulse is short and small, it is named excess of Yin and deficiency of Yang, and sweating may be induced. If the Cun pulse is solid and large, and the Chi pulse is short and small, it is named excess of Yang and deficiency of Yin, and purgation may be used. If the indications for sweating are present but the pulse does not correspond, one must wait until the Chi pulse's force exceeds the Cun pulse before proceeding. If the indications for purgation are present but the pulse does not correspond, one must wait until the Cun pulse's force exceeds the Chi pulse before applying purgation. I privately believe that Yue Ren (Bian Que) posed this difficulty based on symptoms rather than pulses. Why then does his answer rely on pulses rather than symptoms? Moreover, pulses certainly diagnose diseases. If the indications for sweating or purgation are urgent, one cannot delay. Waiting for the pulse to correspond while it has not yet done so creates a dilemma: wanting not to wait causes mental confusion; wanting to wait raises fear of changes in condition. Between these two options, should one follow the symptoms or the pulse? I cannot help but doubt this point.
Someone might question me: Zhang Zhongjing’s *Shanghan Lun* (Treatise on Cold Damage) cites this passage and follows it with the words: "If Guizhi Tang (Cinnamon Twig Decoction) is swallowed, excess Yang leads to death; if Chengqi Tang (Gut-Regulating Decoction) enters the stomach, excess Yin leads to demise." Guizhi Tang is an exterior-releasing formula, and Chengqi Tang is an interior-purging formula; reversing them causes harm, which is indeed true. However, Mahuang Tang (Ephedra Decoction) is also an exterior-releasing formula. Why is it not mentioned? And since you define excess Yin as cold pathogen, and cold pathogen is indeed suitable for Mahuang, why do you cite Guizhi instead?
I reply: Have you not carefully tasted the words of Zhang Zhongjing? He said: "Generally, typhoid diseases mostly arise from Wind-Cold." He also said: "A floating and tight pulse; floating indicates Wind, tight indicates Cold." In the section on Guizhi Tang, he mentions "chilly aversion to cold, shivering aversion to wind"; in the section on Mahuang Tang, he mentions "aversion to wind." If Wind and Cold are distinguished, Wind is Yang and Cold is Yin. However, when Wind operates during times of severe freezing cold in heaven and earth, can it still be called Yang? Thus, Wind and Cold often accompany each other. Therefore, both Guizhi Tang and Mahuang Tang are warm formulas. Using warm formulas for treatment sufficiently demonstrates that both Wind and Cold belong to Yin pathogens. Simply, injury to Wei Qi (Defensive Qi) calls for Guizhi Tang, and injury to Ying Qi (Nutritive Qi) calls for Mahuang Tang. Although Ying and Wei are distinct, their location at the exterior is the same. Zhang Zhongjing’s statement here primarily aims to warn against errors in sweating and purgation, not specifically to distinguish between Ying and Wei. Citing Guizhi Tang implies Mahuang Tang is included therein. What is meant by "excess Yang leads to death" is that when exterior signs have resolved and interior signs are fully established, purgation is indicated but sweating is contraindicated. What is meant by "excess Yin leads to demise" is that when interior signs have not yet manifested and exterior signs exist alone, sweating is indicated but purgation is contraindicated. From this perspective, the original intent of Yue Ren and Zhang Zhongjing can be clearly understood within this context.