伤寒中。有一种极显极要之义。仲景未曾道破。后人暗中摸索。全未道着。只有伤寒偏死下虚人一语是从已败
之后。归咎于病患自己之不慎。而不知其治法之差。用药之误也。夫冬伤于寒者。大率伤于下焦膝胫也。若伤于头
面肩背。是阳气刻刻升越之道。未有不立见恶寒发热者。早伤暮病。夕伤朝病。一汗即邪散而解。且有不汗而自解
者。乌有深入于里。而为六经传变。种种幻证者乎。其所以传变者。正为邪伏于下。与阳气不相冲激。得以宴然久
据。侵淫于里。久而上越。过膝入腹。阳气不得安窟。乃始发病或再加以上焦新感。则其发愈暴。治此者。必选温
散药中之沉降下行者。或温散而佐以沉降之品。导之下行。使邪气之自下而上者。仍退返于下而出焉。则邪气下退。
元气归窟而身安矣。所谓沉降下行之品者。威灵仙独活吴萸沉香牛膝泽泻之属是也。若专以麻桂发其上。上焦得汗。
则上焦元气愈空。下焦邪气。愈因之而上移。是非逐邪也。直驱正以引邪耳。故前人以邪气由太阳下行入少阴。为
深入吾正以邪气由太阳少阴上行入阳明太阴。为深入也。凡发汗后。腹胀满。及水药不得入口者。是不仅中焦湿邪。
为汗所动。而下焦寒邪上越。与中焦之湿邪相搏也。发汗或吐或下后。心下逆满。气上冲胸。及眩悸 振者。是不
仅上焦之清阳经络之津液。为汗所扰而下焦寒邪上越。百脉之气血。举为其所逆乱。不得循经也。下后。脉促胸满。
及胸满烦惊不得小便。谵语。身重不可转侧者。是上脘药力。与下焦寒邪。两寒相搏阳气遏于中焦。而不得舒也。
辨脉篇中。脉浮而大。医反下之。又饮冷水。水寒相得。其人即 。事正类此。即所谓太阳随经。瘀热在里。以致
蓄血发黄。亦是寒邪上争。血脉不得下行之故。总因麻桂。只能发上焦之表汗。不能搜下焦之伏寒。而伤寒为病。
率是邪伏下焦。日久郁极。有触乃发。不在上焦阳气出入之冲道。是以药力不能与之相值。反虚上焦正气为邪气辟
升腾猖獗之路。又何怪乎横肆传变。不可方物哉。或曰太阳病初起。项背强痛。非上焦病乎。此时未闻膝胫有所苦
也。曰项背强痛。正以下焦邪气上冲。而擎之与新感相搏而然。是时两髀以下。必 胀疼痛异常矣。安得谓无苦。
果无苦也。不过寻常感冒而已。何待古今诸贤。费如许心力。故治伤寒。起手必察下焦元气之虚实寒热。虚而寒者。
是真阳不足。即所谓下虚也。温搜兼补之。虚而热者。是燥火也。温搜兼润化之。实而寒者。重温搜之。实而热者。
是邪在外络。而内藏瘀热也。温搜而兼清化之。药力达于病所。使邪从何道而入者。仍从何道而出。而上焦新感之
风寒。即温搜之药。自能随带而解散之。此外如病患脾肺素弱。上焦表湿胶固。中焦痰水凝结。或温热久蕴于中焦
或虚火常冲于头面。皆可随证加药。且明斯义也。凡伤寒而兼香港脚。兼疝气。兼痞块兼饮癖。兼心胃气痛者。举可
赅而治之不犯手矣。即有血块。及脱血症。亦可加行血药。以合治之。而不犯上焦矣。纵横挥洒。无不如志。何至
变证蜂起。触处棘手哉。每见冬月伤寒者。至雨水惊蛰后。或暴呕吐。或暴呃逆。或暴喘促。或暴泻泄。或暴眩晕
心悬。或两腿无力。数武即喘。或二便猝闭。又忽大下。无端烦躁。夜不安眠。或上热下冷。烦躁气喘。半夜后。
又两足转热如焚。此皆遍身筋骨 痛。两髀以下尤甚。第身虽发热而往来无定。不似表证。世遂以为杂病。未有知
是冬寒下伏者。若加以上焦新感。重见恶寒发热。又专以为表证。专以麻桂发之。转见气浮作喘。两腿 肿。元气
不根矣。更有夏暑内伏。交冬。寒邪自下上冲。而始发病者。其证。胸中烦热。如破皮状。两足彻冷如冰。及夜转
热如焚。此寒暑相搏。三焦之血络瘀痹也。益无有知其病情者。
在伤寒病中，有一种极其显著且重要的道理，张仲景未曾点破，后人暗中摸索，完全未能触及。只有“伤寒偏死下虚人”这一句话，是从病人已经败坏之后，归咎于病患自己的不慎，而不知道是治法有误、用药不当造成的。
大凡冬天受寒，大多是在下焦膝胫部位受伤。如果是在头面肩背受伤，那是阳气时刻升发外越的途径，没有不立即出现恶寒发热症状的。早上受寒晚上发病，傍晚受寒早晨发病，一出汗邪气就消散而痊愈，甚至有不通过发汗而自行痊愈的情况。哪里会有邪气深入体内，导致六经传变，出现种种变幻莫测的症状呢？
之所以发生传变，正是因为邪气潜伏在下部，与阳气不相冲激，得以安然长久占据，逐渐侵入体内，时间久了向上蔓延，经过膝盖进入腹部，使得阳气无法安守其位，这才开始发病。如果再叠加上部的新感邪气，那么发病就会更加猛烈。治疗这种情况，必须选择温散药中具有沉降下行作用的药物，或者在温散的同时佐以沉降的药物，引导邪气向下运行，使原本从下往上侵犯的邪气，仍然退回下方并排出体外。这样邪气向下退却，元气回归本位，身体就能安康了。所谓具有沉降下行作用的药物，是指威灵仙、独活、吴茱萸、沉香、牛膝、泽泻这一类药物。如果专门用麻黄、桂枝发上部的汗，上焦得到汗液后，上焦的元气会更加空虚，下焦的邪气反而会因为这种空虚而更加向上移动，这可不是驱逐邪气，简直是驱赶正气来引动邪气罢了。所以前人认为，邪气由太阳经下行进入少阴经，是深入；邪气由太阳、少阴经上行进入阳明、太阴经，也是深入。
凡是发汗后，出现腹胀满，以及水药不能入口的情况，这不仅仅是中焦湿邪被汗动，而是下焦寒邪上越，与中焦的湿邪相互搏结。发汗、催吐或攻下之后，出现心下逆满、气上冲胸，以及眩晕、心悸、身体震颤的情况，这不仅仅是上焦的清阳经络津液被汗扰动，而是下焦寒邪上越，导致全身血脉的气血全部被其逆乱，不能循行经脉。攻下之后，出现脉促、胸满，以及胸满、烦躁惊悸、小便不通、胡言乱语、身体沉重不可转侧的情况，这是上脘的药力与下焦寒邪，两股寒气相互搏结，阳气被遏制在中焦而不能舒展。《辨脉篇》中说，脉象浮大，医生反而使用攻下法，又让病人喝冷水，水寒之气相合，病人就会出现某种症状（原文此处可能有脱字，结合语境指病情加重或出现特定反应），情况正是与此类似。这就是所谓的“太阳随经，瘀热在里”，以致造成蓄血发黄，这也是寒邪向上争竞，血脉不能正常下行的缘故。总的原因在于麻黄、桂枝只能发散上焦的表汗，不能搜剔下焦潜伏的寒邪。而伤寒这类疾病，大多是邪气潜伏在下焦，日久郁积至极，受到触动才发作，并不在上焦阳气出入的要道上，所以药力不能与之相遇抗衡，反而使上焦的正气虚弱，为邪气开辟升腾猖獗的道路，又有什么奇怪的呢？邪气横行肆虐，传变不可预测，难道不是因为这个原因吗？
有人问：太阳病初起时，项背部强痛，这不是上焦的病吗？此时没听说膝胫有什么痛苦啊。回答说：项背部强痛，正是因为下焦邪气上冲，支撑着它与新感邪气相互搏结所致。在这个时候，两大腿以下必然感到胀满疼痛异常。怎么能说没有痛苦呢？如果真的没有痛苦，不过是普通的感冒而已，何必等待古今各位贤能之人费如此大的心力去研究呢？
所以治疗伤寒，起手时必须察看下焦元气的虚实寒热。如果是虚而寒，就是真阳不足，也就是所谓的“下虚”，需要用温补兼搜剔的方法治疗。如果是虚而热，就是燥火，需要用温补兼滋润化解的方法治疗。如果是实而寒，需要重温补搜剔的方法。如果是实而热，就是邪气在外络，而内脏有瘀热，需要用温补搜剔兼清化热邪的方法治疗。药力到达病所，使邪气从哪里进来的，仍然从哪条路出去，而上焦新感受的风寒，也能随着温搜的药物自然解散。此外，如病人脾肺素来虚弱，上焦表湿胶固难解，中焦痰水凝结，或者温热久蕴于中焦，或者虚火常冲于头面，都可以随证加入相应的药物。明白了这个道理，凡是伤寒兼有脚气、疝气、痞块、饮癖、心胃气痛的，都可以概括性地治疗而不必动手费力。即使有血块及失血症，也可以加入活血药物配合治疗，而不损伤上焦。这样纵横挥洒，无不如愿，怎么会变证蜂起，处处棘手呢？
我常见到冬天患伤寒的人，到了雨水、惊蛰节气之后，突然剧烈呕吐，或者突然呃逆，或者突然气喘急促，或者突然腹泻，或者突然眩晕、心中悬空感，或者双腿无力，走几步路就喘，或者大小便突然闭塞，又或者突然大量泄泻，无缘无故烦躁，夜间不能安眠，或者上热下冷、烦躁气喘，半夜以后，双脚又变得灼热如火。这些都是遍身筋骨疼痛，大腿以下尤其严重。虽然身体发热，但热度往来不定，不像表证。世人于是把它当作杂病，没有人知道这是冬天寒邪潜伏在下焦所致。如果再叠加上部的新感，重新出现恶寒发热，又专门当作表证，专门用麻黄、桂枝发汗，反而出现气浮作喘，双腿浮肿，元气失去根基了。更有夏天暑气内伏，交入冬天，寒邪自下向上冲撞才开始发病的，其症状表现为胸中烦热，像皮肤破裂一样的感觉，双脚彻骨寒冷如冰，到了夜晚又转为灼热如火。这是寒暑相互搏结，三焦的血络瘀阻痹塞所致。更没有知道这种病情的人。
In the context of *Shanghan* (Cold Damage), there is a principle that is extremely prominent and crucial, which Zhang Zhongjing did not explicitly state. Later generations groped in the dark, completely failing to grasp it. The only phrase that hints at this is "Shanghan tends to kill those with deficiency in the lower jiao," but this is often interpreted retrospectively after the patient's condition has deteriorated, blaming the patient's own lack of caution, rather than recognizing the errors in treatment methods and medication.
Generally speaking, when one contracts cold in winter, the injury usually occurs in the lower jiao, specifically around the knees and shins. If the injury occurs on the head, face, shoulders, or back, these are pathways where yang qi constantly ascends and disperses outward; consequently, symptoms such as aversion to cold and fever would appear immediately. Whether contracted in the morning and manifesting in the evening, or contracted in the evening and manifesting in the morning, the pathogen typically dissipates upon sweating, and sometimes resolves spontaneously without sweating. How could it possibly penetrate deeply into the interior, leading to transmission through the six meridians and presenting various illusory or complex syndromes?
The reason for such transmission lies precisely in the fact that the pathogen is latent in the lower part, not clashing with yang qi, allowing it to reside peacefully for a long time. It gradually invades the interior, and over time, rises upward, passing the knees and entering the abdomen. This prevents yang qi from settling in its proper residence, thereby triggering the onset of disease. If this is compounded by a new external contraction in the upper jiao, the onset will be even more violent. To treat this, one must select warming and dispersing herbs that possess sinking and descending properties, or add such agents to warming and dispersing formulas to guide the pathogen downward. This allows the pathogen, which originally invaded from below upwards, to retreat back to the lower jiao and exit from there. When the pathogen retreats downward, the primordial qi returns to its root, and the body becomes secure. Herbs with sinking and descending properties include *Weilingxian* (Clematis Root), *Duhuo* (Angelicae Pubescentis Radix), *Wuzhuyu* (Evodiae Fructus), *Chenxiang* (Aquilariae Lignum), *Niuxi* (Achyranthis Bidentatae Radix), and *Zexie* (Alismatis Rhizoma). If one exclusively uses *Mahuang* (Ephedrae Herba) and *Guizhi* (Cinnamomi Ramulus) to induce sweating in the upper jiao, the upper jiao's primordial qi will become increasingly empty after sweating. Consequently, the pathogen in the lower jiao will shift further upward due to this emptiness. This is not expelling the pathogen; it is essentially driving the healthy qi to invite the pathogen inward. Therefore, ancient practitioners considered the pathogen moving from the Taiyang meridian down to the Shaoyin meridian as "deepening," and moving from Taiyang/Shaoyin up to the Yangming/Taiyin meridians as also "deepening."
After inducing sweating, if abdominal distension and fullness occur, along with the inability to retain water or medicine, this indicates not only that damp-heat in the middle jiao has been disturbed by sweat, but also that cold-pathogen from the lower jiao has risen upward and clashed with the dampness in the middle jiao. After sweating, vomiting, or purging, if epigastric fullness with a sensation of rebellion, Qi rushing up to the chest, dizziness, palpitations, and tremors occur, this signifies not merely the disturbance of clear Yang and fluids in the upper jiao meridians by sweat, but the upward surge of lower jiao cold-pathogen causing chaotic reversal of Qi and blood in all vessels, preventing them from following their normal meridional courses. After purging, if rapid pulse, chest fullness, irritability, fright, inability to urinate, delirium, and heaviness of the body preventing turning occur, this results from the clash between the residual medicinal force in the upper stomach and the lower jiao cold-pathogen. Two types of cold clash, suppressing Yang qi in the middle jiao and preventing its free flow. In the *Bian Mai Pian* (Chapter on Pulse Differentiation), it states: if the pulse is floating and large, and the physician erroneously uses purgation, followed by drinking cold water, the combination of water and cold will cause specific adverse reactions, similar to the cases described above. This corresponds to the concept of "Taiyang following the meridian, with stasis-heat residing in the interior," leading to blood accumulation and jaundice. This too is caused by cold-pathogen contesting upward, preventing blood vessels from flowing downward normally. The fundamental reason is that *Mahuang* and *Guizhi* can only induce sweating from the exterior of the upper jiao, but cannot search out and eliminate the latent cold in the lower jiao. Diseases of Shanghan are typically characterized by pathogens latent in the lower jiao, accumulating depression for a long time until triggered. They do not reside in the critical pathways of Qi and blood entry and exit in the upper jiao. Therefore, medicinal power cannot encounter them directly. Instead, it weakens the upright Qi in the upper jiao, paving the way for the pathogen to rise wildly and aggressively. Is it surprising then that the pathogen spreads uncontrollably and changes unpredictably?
One might ask: At the initial stage of Taiyang disease, stiffness and pain in the neck and back—are these not diseases of the upper jiao? At this time, is there no discomfort in the knees and shins? I reply: The stiffness and pain in the neck and back are precisely caused by the lower jiao pathogen rushing upward, supporting itself against the new external contraction. At this moment, the area below both thighs must surely feel abnormal distension and pain. How can one say there is no discomfort? If there were truly no discomfort, it would merely be a common cold, requiring no extensive effort from sages past and present to analyze.
Therefore, when treating Shanghan, one must first examine the deficiency/excess and cold/heat status of the Yuan Qi (Primordial Qi) in the lower jiao. If deficient and cold, it indicates insufficiency of True Yang, known as "lower jiao deficiency"; treatment requires warming, searching out the pathogen, and tonifying. If deficient and hot, it indicates dryness-fire; treatment requires warming, searching out, and moistening/dissolving. If excess and cold, treatment requires strong warming and searching out. If excess and hot, it indicates pathogen in the exterior collaterals with internal stasis-heat; treatment requires warming, searching out, and clearing/dissolving heat. When medicinal power reaches the site of the disease, the pathogen exits via the same route it entered, and any new wind-cold in the upper jiao will naturally dissipate alongside the warming/searching herbs. Furthermore, if a patient has inherent weakness of Spleen and Lung, stubborn dampness in the upper jiao exterior, phlegm-fluid retention in the middle jiao, prolonged heat accumulation in the middle jiao, or deficient fire frequently rising to the head and face, appropriate herbs can be added according to the syndrome. Understanding this principle allows one to comprehensively treat Shanghan complicated by Hong Kong foot (gouty arthritis/jiaojixi), hernia, masses, fluid retention, or heart-stomach Qi pain, without needing excessive manual intervention. Even with blood masses or hemorrhagic conditions, blood-invigorating herbs can be added to the treatment without damaging the upper jiao. One can thus maneuver freely and effectively, avoiding the proliferation of complicated syndromes and difficult-to-handle situations.
I often see patients who contracted cold in winter developing symptoms after the Rain Water or Awakening of Insects solar terms: sudden severe vomiting, hiccups, dyspnea, diarrhea, vertigo with a feeling of emptiness in the chest, weakness in the legs leading to panting after walking only a few steps, sudden obstruction of urination and defecation, or sudden profuse diarrhea, inexplicable irritability, insomnia, upper heat with lower cold, irritability and wheezing, or feet becoming burning hot after midnight. These are accompanied by pain throughout the bones and sinews, especially severe below the thighs. Although the body is febrile, the heat comes and goes irregularly, unlike exterior syndromes. The world mistakenly classifies these as miscellaneous diseases, unaware that they stem from latent winter cold in the lower jiao. If combined with a new upper jiao contraction, reappearing as aversion to cold and fever, and treated solely as an exterior syndrome with *Mahuang* and *Guizhi*, it leads to floating Qi causing wheezing, edema in the legs, and loss of the root of Yuan Qi. Additionally, there are cases where summer-heat was latent internally, and upon entering winter, cold-pathogen surged upward from below, triggering illness. Symptoms include vexing heat in the chest resembling skin rupture, ice-cold feet, and feet becoming burning hot at night. This is due to the clash of cold and heat causing stasis and obstruction in the blood collaterals of the three jiaos. Such conditions are rarely understood by practitioners.