桂枝，味甘、辛，气大热，浮也，阳中之阳，有小毒。乃肉桂之梢也，其条如柳，故又
曰柳
桂。能治上焦头目，兼行于臂，调荣血，和肌表，止烦出汗，疏邪散风。入足太阳之腑，乃
治伤寒之要药，但其中有宜用不宜用之分，辨之不明，必至杀人矣。夫桂枝乃太阳经之药，
邪入太阳，则头痛发热矣。凡遇头痛身热之症，桂枝当速用以发汗，汗出则肌表和矣。夫人
身有荣卫之分，风入人身，必先中于卫，由卫而入营，由营卫而入腑，由腑而入脏，原有次
第，而不可紊也。太阳病，头痛而身热，此邪入于卫，而未入
于营，桂枝虽是太阳经之药，但能祛入卫之邪，不能祛入营之邪也。凡身热而无头疼之症，
即非太阳之症，不可妄用桂枝。即初起身热头疼，久则头不疼，而身尚热，此又已离太阳，
不可妄用桂枝矣。且桂枝乃发汗之药也，有汗宜止，无汗宜发，此必然之理也。然而有有汗
之时，仍可发汗；无汗之时，不可发汗者，又不可不辨。伤寒汗过多者，乃用他药以发汗，
以至汗出过多，而太阳头痛尚未解，故不可不仍用桂枝以和解，非恶桂枝能闭汗也。伤寒无
汗，正宜发汗，乃发汗而竟至无汗，此外邪尽解，不止太阳之邪亦解也，故不可轻用桂枝，
以再疏其腠理，非防桂枝能出汗也。知其宜汗、不宜汗之故，辨其可汗、不可汗之殊，用桂
枝祛邪，自无舛错，又何至动辄杀人耶。
或谓桂枝发汗，亦能亡阳，何故仲景张公全然罔顾。凡有表症未散者，须用桂枝汤，吾
甚惧
之，而不敢多用也。嗟乎！桂枝解表之药，非亡阳之药也，用桂枝汤而亡阳者，乃不宜解表
，而妄用桂枝以表散，遂至变症蜂起，于桂枝何咎哉。
或谓桂枝汤，治寒伤卫之圣药，凡身热而有头痛项强之症，用桂枝汤仍然不除，反加沉
重者
，又何说也？此必多用桂枝以致此也。夫太阳经者，阳经也。桂枝，热药也。寒气初入于太
阳，寒犹未甚，少用桂枝以祛邪，则太阳之火自安，而寒邪畏热而易解；若多用桂枝，则味
过于热，转动太阳之火，热以生热，反助胃火之炎，而寒邪乘机亦入于胃，寒亦变为热，而
不一解，而太阳之本症仍在也。故用桂枝者，断不可用多以生变，惟宜少用以祛邪也。
或疑桂枝汤之治伤寒，以热散寒也。以热散寒，祛寒出外，非祛汗出外也，何以有亡阳
之虑
？想非伤寒而误用桂枝也，夫用桂枝汤，必须冬日之患伤寒，而又兼头痛项强者，才是寒伤
卫之症。伤寒若不是冬天发热，即发热而不头痛项强，皆非伤寒入卫之症，安得不变为亡阳
之祸，非桂枝之过也。
或疑桂枝汤宜用而不用，以致传入于各经，而头痛项强如故，不识桂枝汤仍可用否？夫
寒伤
卫，而不速用桂枝以散表，致邪入于里，自应急攻其里矣。但头痛项强如故，此邪犹留于卫
也，虽其病症似乎变迁之不定，然正喜其邪留于太阳之经，在卫而不尽入于里，仍用桂枝汤
，而少轻其分两，多加其邪犯何经之药，则随手奏功也。不可因日数之多，拘拘而专攻其入
里之一经耳。
或疑桂枝性热，麻黄性寒，性同冰炭，何以解太阳之邪，而仲景张公且有合用之出奇乎？
曰
∶识得阴阳之颠倒，寒热之异同，始可用药立方，以名神医也。夫人身荣、卫之不同也，邪
入卫则寒，邪入荣则热，正不可谓荣、卫俱属太阳，混看而不分别也。桂枝祛卫中之寒，麻
黄祛营中之热。桂枝、麻黄合用，祛荣、卫寒热之半，又何疑乎。惟邪将入于营，未离于卫
，或寒多而热少，或寒少而热多之间，倘分解之未精，治疗之不当，恐不能速于解邪，转生
他变耳。然在仲景夫子，桂枝、麻黄合用，立方固未尝不奇而且神也。
或疑桂枝散寒邪，散卫中之邪也，一用桂枝，宜卫中之寒邪尽散矣，何以又使其入于营
中也
。似乎桂枝不能尽散卫中之邪也，不知可别有他药佐桂枝之不足乎？曰∶桂枝散卫中之寒，
吾虑其有余，而君虑其不足乎。用桂枝汤，而邪入于营者，非桂枝之不足以散卫中之邪，乃
迟用桂枝，而邪已先入于荣中，桂枝将奈何哉。此伤寒之病，所以贵疗之早也。
或疑桂枝汤，伤寒症祛邪之先锋也，用之当，则邪易退，用之不当，则邪难解。首先用
桂枝
汤，何以使之无不当耶。夫治伤寒而不知症，用药未有不误者也。故古人有看症不看脉之论
，然而脉亦未可不讲也。仲景夫子论症，未尝不论脉，而无如世人之昧昧也。读仲景夫子
伤寒之书，亦何至首先用桂枝汤而有误者乎。南昌喻嘉言尚论仲景夫子伤寒之书，卓识
明眼
，超越前人，近今未有其亚。但其中少有异同，铎不揣再为辨论，庶可免舛错之讥，则自今
以后，读伤寒之书，亦何至于昏昧哉。
桂枝，味道甘、辛，气性大热，药势上浮，属于阳中的阳，有微小的毒性。它是肉桂的嫩梢部分，枝条像柳树一样，所以又叫做柳桂。它能治疗上焦头目部的疾病，兼能通行于手臂，调和营血，和解肌表，止住烦渴并促使出汗，疏散邪气、驱散风邪。它进入足太阳膀胱腑，是治疗伤寒的关键药物，但其中有用法适宜和不适宜的区别，如果辨别不清楚，必然会导致死亡。
桂枝是足太阳经的药物，邪气侵入太阳经，就会出现头痛、发热的症状。凡是遇到头痛身热的病症，应当迅速使用桂枝来发汗，汗出之后肌表就调和了。人的身体有营气和卫气的区别，风邪侵入人体，必定先伤及卫气，由卫气传入营气，再由营卫传入腑，由腑传入脏，这原本是有次序的，不能紊乱。
太阳病，出现头痛且身热，这是邪气侵入卫分，而尚未侵入营分。桂枝虽然是太阳经的药物，但只能祛除侵入卫分的邪气，不能祛除侵入营分的邪气。凡是身热而没有头痛症状的，就不是太阳病的症状，不可以胡乱使用桂枝。即使是初起时身热头痛，久了之后头不疼了，但身体仍然发热，这又是已经离开太阳经了，不可以胡乱使用桂枝。
况且桂枝是发汗的药物，有汗的情况应该止汗，无汗的情况应该发汗，这是必然的道理。然而，在有汗的时候，仍然可以发汗；在无汗的时候，不可以发汗，这些情况又不可以不加以辨别。伤寒病患者如果因为服用其他药物发汗而导致汗出过多，致使太阳经的头痛还没有解除，所以不得不继续使用桂枝来和解表里，这并不是说害怕桂枝会闭塞汗孔。
伤寒无汗，正适合发汗，但如果发了汗之后竟然还是没有汗，这说明外邪已经完全解除，不仅仅是太阳经的邪气解除了，所以不可以轻易使用桂枝，以免再次疏泄腠理，这并不是担心桂枝会导致出汗。明白了适宜发汗和不适宜发汗的原因，辨别了可以发汗和不可以发汗的不同，使用桂枝来祛除邪气，自然就不会出错，又怎么会动辄导致死亡呢？
有人问：桂枝发汗，也能导致亡阳，为什么张仲景先生完全不顾这一点呢？凡是有表证没有解散的，必须使用桂枝汤，我非常担心这一点，所以不敢多用。唉！桂枝是解表的药物，不是亡阳的药物。使用桂枝汤而导致亡阳的，是因为本不应该解表，却胡乱使用桂枝进行表散，从而导致各种变症蜂拥而起，这怪桂枝有什么罪过呢？
有人问：桂枝汤是治疗寒邪伤及卫气的圣药，凡是身热且有头痛项强（脖子僵硬）症状的，使用桂枝汤仍然不能消除，反而病情加重的，又作何解释？这一定是因为多用桂枝导致的。太阳经是阳经。桂枝是热性的药物。寒气刚刚侵入太阳经，寒邪还不严重，少用桂枝来祛除邪气，那么太阳经的火气自然安定，而寒邪畏惧热气就容易解除；如果多用桂枝，那么味道过于热，会扰动太阳经的火气，热上加热，反而助长胃火的炎上，而寒邪趁机也进入胃中，寒也变成了热，而且不能一并解除，太阳经的本症依然存在。所以使用桂枝的人，绝对不可以多用以致产生变症，只宜少用来祛除邪气。
有人怀疑桂枝汤治疗伤寒，是用热性来散发寒邪。用热性散发寒邪，是将寒邪驱逐出去，而不是将汗液驱逐出去，为什么会有亡阳的忧虑？我想这是因为并非伤寒而误用了桂枝。使用桂枝汤，必须是冬天患伤寒，并且兼有头痛项强的症状，这才是寒邪伤及卫气的病症。如果是冬天以外的季节发热，或者发热但不头痛项强，都不是伤寒入卫的病症，怎么能不变成亡阳的祸害呢？这不是桂枝的过错。
有人怀疑桂枝汤应该使用却没有使用，导致邪气传入各条经络，头痛项强依旧，不知道桂枝汤是否还可以使用？寒邪伤及卫气，如果不迅速使用桂枝来发散表邪，导致邪气传入体内，自然应该紧急攻治里证。但是头痛项强依旧，这说明邪气还留在卫分，虽然病症似乎变化不定，但这正是庆幸邪气留在太阳经，在卫分而没有完全进入体内，仍然可以使用桂枝汤，只是减轻其分量，多加一些针对邪气侵犯哪条经络的药物，就能随手奏效。不可以因为患病天数多，就拘泥地专门攻治传入体内的某一条经络。
有人怀疑桂枝性热，麻黄性寒，性质如同冰炭不同，为什么能共同解除太阳经的邪气，而且张仲景先生甚至有合用的奇妙之处呢？回答说：懂得了阴阳的颠倒、寒热的异同，才可以用药立方，称为神医。人体的营气和卫气是不同的，邪气侵入卫分则表现为寒，邪气侵入营分则表现为热，绝不能说营、卫都属于太阳经，就混在一起看而不加分别。桂枝祛除卫分中的寒邪，麻黄祛除营分中的热邪。桂枝和麻黄合用，同时祛除营、卫中一半的寒热之邪，这有什么可怀疑的呢？只有当邪气将要进入营分，尚未离开卫分，或者寒多热少，或者寒少热多的时候，如果分解得不精细，治疗不得当，恐怕不能快速解除邪气，反而会产生其他变症罢了。然而在张仲景夫子那里，桂枝和麻黄合用，处方固然既奇妙又神妙。
有人怀疑桂枝散寒邪，是散卫分中的邪气，一旦使用桂枝，卫分中的寒邪应该全部散尽了，为什么又会让邪气进入营分呢？似乎桂枝不能完全散尽卫分中的邪气。不知道是否可以有其他药物辅助桂枝的不足吗？回答说：桂枝散卫分中的寒邪，我担心它有余，而你却担心它不足吗？使用桂枝汤后，邪气进入营分，并不是桂枝不足以散尽卫分中的邪气，而是因为使用桂枝太迟，邪气已经先进入了营分，桂枝又能怎么办呢？这就是伤寒病之所以贵在早期治疗的原因。
有人怀疑桂枝汤是伤寒症祛除邪气的先锋，使用得当，邪气容易退去，使用不当，邪气难以解除。首先使用桂枝汤，怎么能让它没有不当之处呢？治疗伤寒而不懂辨证，用药没有不出错的。所以古人有只看症状不看脉象的说法，然而脉象也是不可不讲求的。张仲景夫子论述症状，未曾不论述脉象，无奈世人愚昧无知。研读张仲景夫子的《伤寒论》，又何至于首先使用桂枝汤而出错呢？南昌人喻嘉言推崇评论张仲景夫子的《伤寒论》，见识卓越，眼光明亮，超越前人，近代没有人能比得上他。但其中稍有异同，我不自量力再加以辨论，或许可以避免被讥笑为错误的嫌疑，那么从今以后，读《伤寒论》的书，又何至于昏昧无知呢？
Cassiae Ramulus (Guizhi), with a sweet and pungent taste, possesses a strongly hot nature. It is ascending and belongs to the Yang within Yang. It has slight toxicity. It is the tender tip of Cinnamomi Cortex (Rougui, 肉桂). Its branches resemble those of willow trees, hence it is also called Willow Cinnamon (Liugui, 柳桂). It can treat diseases of the head and eyes in the Upper Jiao (Upper Burner), simultaneously circulating through the arms, harmonizing Ying Blood (Nutritive Blood) and the Muscle Layer (Muscular Level), stopping thirst and inducing sweating, and dispersing pathogenic factors and wind. It enters the Bladder Fu Organ (Bladder Bowel), making it a crucial herb for treating Cold Damage (Shanghan, 伤寒). However, there are indications for its appropriate and inappropriate use; if this distinction is not clearly understood, it may lead to death.
Cassiae Ramulus is an herb of the Foot-Taiyang Meridian (Foot Taiyang Channel). When pathogens enter the Taiyang meridian, headache and fever occur. In cases of headache and fever, Cassiae Ramulus should be used promptly to induce sweating; once sweat is produced, the Muscle Layer is harmonized. The human body is divided into Ying (Nutritive) and Wei (Defensive) aspects. When wind pathogens invade the body, they first affect the Wei aspect, then move from Wei to Ying, from Ying-Wei to the Fu organs, and from Fu to the Zang organs. This progression follows a specific order and must not be disordered.
In Taiyang disease, characterized by headache and fever, the pathogen has entered the Wei aspect but has not yet entered the Ying aspect. Although Cassiae Ramulus is an herb of the Taiyang meridian, it can only dispel pathogens that have entered the Wei aspect, not those that have entered the Ying aspect. In cases where there is fever without headache, it is not a Taiyang syndrome, and Cassiae Ramulus should not be used indiscriminately. Even if initially there is fever and headache, but later the headache ceases while fever persists, the condition has left the Taiyang stage, and Cassiae Ramulus should not be used indiscriminately.
Moreover, Cassiae Ramulus is an herb that induces sweating. When sweat is present, sweating should be stopped; when sweat is absent, sweating should be induced. This is an inevitable principle. However, one must distinguish between situations where sweating can be induced despite existing sweat, and situations where sweating should not be induced despite the absence of sweat. If a patient with Cold Damage has sweated excessively due to other herbs, and the Taiyang headache remains unresolved, Cassiae Ramulus must still be used to harmonize the exterior. This is not because we fear that Cassiae Ramulus will close the pores. Conversely, in Cold Damage with no sweat, sweating is indicated. If sweating fails to produce sweat after administration, it indicates that external pathogens have completely resolved, including those in the Taiyang meridian. Therefore, Cassiae Ramulus should not be lightly used to further open the interstices (Couli, 腠理). This is not out of fear that Cassiae Ramulus will cause excessive sweating. Understanding the reasons for inducing or not inducing sweating, and distinguishing between conditions suitable or unsuitable for sweating, ensures that using Cassiae Ramulus to dispel pathogens will result in no errors, preventing accidental deaths.
Some argue: "Cassiae Ramulus induces sweating and can also cause Yang Collapse (Wangyang, 亡阳). Why did Master Zhang Zhongjing (Zhang Zhongjing, 张仲景) completely overlook this?" For any exterior syndrome that has not dispersed, Guizhi Tang (Cinnamon Twig Decoction) must be used. I am very cautious about this and dare not use it in large doses. Alas! Cassiae Ramulus is an exterior-resolving herb, not a herb causing Yang Collapse. Cases of Yang Collapse following the use of Guizhi Tang occur because the herb was used improperly to resolve the exterior when it was contraindicated, leading to numerous complications. What fault does Cassiae Ramulus bear?
Some ask: "Guizhi Tang is the sacred medicine for cold damaging the Wei aspect. If a patient presents with fever, headache, and neck stiffness, and Guizhi Tang fails to relieve symptoms, instead worsening them, how is this explained?" This is likely due to the excessive use of Cassiae Ramulus. The Taiyang meridian is a Yang meridian. Cassiae Ramulus is a hot herb. When cold qi first enters the Taiyang meridian, the cold is not severe. Using a small dose of Cassiae Ramulus to dispel pathogens allows the fire of the Taiyang meridian to remain calm, making the cold pathogen fearful of heat and easy to resolve. However, using too much Cassiae Ramulus makes the flavor overly hot, stirring up the fire of the Taiyang meridian. Heat generates more heat, assisting the flaming fire of the Stomach, allowing cold pathogens to enter the Stomach. The cold transforms into heat, failing to resolve, while the original Taiyang symptoms persist. Therefore, when using Cassiae Ramulus, one must absolutely avoid excessive use which causes changes; it is best used in small doses to dispel pathogens.
Some doubt: "Guizhi Tang treats Cold Damage by using heat to scatter cold. Scattering cold outward is not expelling sweat outward. Why is there concern about Yang Collapse?" I suspect this arises from misusing Guizhi Tang in non-Cold Damage cases. To use Guizhi Tang correctly, the patient must have contracted Cold Damage in winter and present with headache and neck stiffness. These are signs of cold damaging the Wei aspect. If fever occurs outside of winter, or if there is fever without headache and neck stiffness, these are not signs of Cold Damage invading the Wei aspect. How could this not result in the disaster of Yang Collapse? This is not the fault of Cassiae Ramulus.
Some doubt: "If Guizhi Tang is not used when indicated, allowing pathogens to transmit to other meridians, leaving headache and neck stiffness unchanged, can Guizhi Tang still be used?" When cold damages the Wei aspect and Guizhi Tang is not used promptly to scatter the exterior, allowing pathogens to enter the interior, emergency treatment should target the interior. However, if headache and neck stiffness persist, the pathogen remains in the Wei aspect. Although symptoms seem variable, it is fortunate that the pathogen remains in the Taiyang meridian, in the Wei aspect, and has not fully entered the interior. One can still use Guizhi Tang, reducing its dosage and adding herbs targeting the specific meridian invaded by the pathogen, achieving immediate results. One should not be rigidly confined to attacking only the interior meridian simply because many days have passed.
Some doubt: "Cassiae Ramulus is hot, while Ephedrae Herba (Mahuang, 麻黄) is cold. Their natures are like ice and charcoal. How can they jointly resolve Taiyang pathogens? Moreover, Master Zhang Zhongjing uses them together in a miraculous manner." The answer is: Only by understanding the inversion of Yin and Yang, and the similarities and differences of cold and heat, can one prescribe medicines and be called a divine physician. The difference between Ying and Wei in the human body is significant. When pathogens enter the Wei aspect, cold manifests; when they enter the Ying aspect, heat manifests. One cannot mistakenly view Ying and Wei as belonging solely to the Taiyang meridian without distinction. Cassiae Ramulus dispels cold in the Wei aspect, while Mahuang dispels heat in the Ying aspect. Using Cassiae Ramulus and Mahuang together dispels half of the cold and heat in the Ying and Wei aspects. What is there to doubt? Only when pathogens are on the verge of entering the Ying aspect but have not left the Wei aspect, presenting with either more cold and less heat, or less cold and more heat, might imprecise differentiation and improper treatment fail to quickly resolve pathogens and instead generate other complications. However, in the hands of Master Zhang Zhongjing, combining Cassiae Ramulus and Mahuang is indeed both miraculous and divine.
Some doubt: "Cassiae Ramulus scatters cold pathogens, specifically those in the Wei aspect. Once Cassiae Ramulus is used, shouldn't all cold pathogens in the Wei aspect be scattered? Why would pathogens then enter the Ying aspect? It seems Cassiae Ramulus cannot fully scatter pathogens in the Wei aspect. Could there be other herbs to supplement the insufficiency of Cassiae Ramulus?" The answer is: Regarding Cassiae Ramulus scattering cold in the Wei aspect, I worry it may be excessive, while you worry it may be insufficient. If pathogens enter the Ying aspect after using Guizhi Tang, it is not because Cassiae Ramulus is insufficient to scatter Wei pathogens, but because Cassiae Ramulus was used too late, allowing pathogens to enter the Ying aspect first. What can Cassiae Ramulus do then? This is why early treatment is prized in Cold Damage.
Some doubt: "Guizhi Tang is the vanguard for dispelling pathogens in Cold Damage. Used appropriately, pathogens retreat easily; used inappropriately, they are hard to resolve. How can we ensure the initial use of Guizhi Tang is never inappropriate?" Treating Cold Damage without proper syndrome differentiation leads inevitably to erroneous medication. Hence, ancients spoke of observing symptoms without examining pulses, yet pulse diagnosis is also indispensable. Master Zhang Zhongjing discussed symptoms without neglecting pulses, but unfortunately, people today are ignorant. By studying Master Zhang Zhongjing's *Treatise on Cold Damage* (Shanghan Lun, 《伤寒论》), how could one make errors by initially using Guizhi Tang? Yu Jiayan (Yu Jiayan, 喻嘉言) of Nanchang praised and analyzed Master Zhang Zhongjing's work with profound insight and clear vision, surpassing predecessors, unmatched in recent times. However, where minor discrepancies exist, I venture to debate again, hoping to avoid criticism of error. Thus, from now on, reading *Cold Damage* texts, one need not remain ignorant.