疫疹之脉，未有不数者。有浮大而数者，有沉细而数者，有不浮不沉而数者，有按之若隐若现者，此《灵枢》所谓
阳毒伏匿之象也。诊其脉，即知其病之吉凶。浮大而数者，其毒发扬，一经表热，病自霍然；沉细而数者，其毒已深，
大剂清解，犹易扑灭；至于若隐若现，或全伏者，其毒重矣，其症险矣。此脉得于初起者间有。得于七、八日者颇多，
何也？医者初认为寒，重用发表，先亏其阳；表则不散，继之以下，又亏其阴。殊不知伤寒五、六日不解，法在当
下，尤必审其脉之有力者宜之。疫症者，四时不正之疠气。夫疠气，乃无形之毒，胃虚者感而受之，病形颇
似大实，而脉象细数无力。若以无形之疠气，而当硝、黄之猛烈，邪毒焉有不乘虚而入耶？弱怯之人，不为
阳脱，即为阴脱；气血稍能驾御者，必至脉转沉伏，变症蜂起，或四肢逆冷，或神昏谵语，或郁冒直
视，或遗尿、旁流，甚至舌卷囊缩，循衣摸床，种种恶症，颇类伤寒。医者不悟引邪入内，阳极似阴，而
曰变成阴症，妄投参、桂，死如服毒，遍身青紫，鼻口流血。如未服热药者，即用大剂败毒饮，重加石膏，
或可挽回。予因历救多人，故表而出之。
乾隆戊子年，吾邑疫疹流行，一人得病，传染一家，轻者十生八、九，重者十存一、二，合境之内，
大率如斯。初起之时，先恶寒而后发热，头痛如劈，腰如被杖，腹如搅肠，呕泄兼作，大小同病，万人一
辙。有作三阳治者，有作两感治者，有作霍乱治者。迨至两日，恶候蜂起，种种危症，难以枚举。如此而
死者，不可胜计。此天时之疠气，人竟无可避者也。原夫至此之由，总不外乎气运。人身一小天地，天地
有如是之疠气，人即有如是之疠疾，缘戊子岁少阴君火司天，大运主之，五、六月间，又少阴君火，加以
少阳相火，小运主之，二之气与三之气合行其令，人身中只有一岁，焉能胜烈火之亢哉？医者不按运气，固
执古方，百无一效。或有疑而商之者，彼即朗诵陈言，援以自证。要之执伤寒之法以治疫，焉有不
死者乎？是人之死，不死于病而死于药，不死于药而竟死于执古方者之药也。予因运气，而悟疫症乃胃受
外来之淫热，非石膏不足以取效耳！且医者意也，石
膏者寒水也，以寒胜热，以水克火，每每投之百发百中。五月间余亦染疫，凡邀治者，不能亲身诊视，叩
其症状，录受其方，互相传送，活人甚众。癸丑京师多疫，即汪副宪、冯鸿胪亦以予方传送，服他药
不效者，俱皆霍然。故笔之于书，名曰清瘟败毒饮，随症加减，详列于后，并付治验。
疫疹的脉象，没有不是数脉的。有的浮大且数，有的沉细且数，有的不浮不沉而数，有的按下去若隐若现，这是《灵枢》所说的阳毒潜伏隐匿的现象。诊察它的脉象，就能知道病情的吉凶。脉象浮大而数的，说明邪毒正在发散，属于一经表热证，病情自然很快痊愈；脉象沉细而数的，说明邪毒已经深入，用大剂量的清热解表药，还容易扑灭；至于脉象若隐若现，或者完全伏匿不见的，说明邪毒很重，症状也很危险。这种脉象在疾病初起时偶尔见到。在发病第七、八天出现的却很多，为什么呢？因为医生起初误认为是伤寒，重用发汗解表的药物，先损伤了阳气；表证不解，接着又用泻下法，又损伤了阴液。殊不知伤寒病到了第五、六天还不解除，治法应当使用攻下法，但必须仔细审察脉象有力者才适用。疫病，是四时不正的疠气。疠气，是无形的毒邪，胃气虚弱的人感受了它而患病，病形看起来很像是实证，但脉象却是细数无力的。如果用无形的疠气，去抵挡硝石、大黄这样猛烈的药物，邪毒怎么会不乘虚而入呢？体质虚弱的人，不是发生阳气外脱，就是发生阴液外脱；气血稍微能够支撑的人，必然导致脉象转为沉伏，变证蜂拥而起，或者四肢逆冷，或者神志昏迷胡言乱语，或者郁闷昏冒两眼直视，或者遗尿、大便失禁，甚至舌体卷缩睾丸收缩，循衣摸床，种种恶症，很类似伤寒。医生不明白这是引邪入内，阳极似阴，反而说是变成了阴证，妄加人参、肉桂等温热药，病人死得就像服了毒药一样，全身青紫，鼻口流血。如果没有服用热药的人，就立即用大剂量的败毒饮，重加石膏，或许还可以挽回。我因此救治了很多人，所以把它写出来公布于世。
乾隆戊子年，我们县瘟疫流行，一个人得病，传染全家，轻的病人十人能救活八九个，重的病人十人只能救活一两个，全县境内，大体都是这样。初起的时候，先怕冷然后发热，头痛得像要劈开一样，腰像被棍棒打过一样痛，肚子像肠子搅动一样痛，呕吐和腹泻同时发作，大人小孩都得同样的病，万人情况都一样。有的医生当作三阳经病治疗，有的当作两感病治疗，有的当作霍乱治疗。等到两天后，凶险的症状蜂拥而起，种种危重病症，难以一一列举。像这样死亡的，不可胜数。这是天时的疠气，人们竟然无法躲避。推究到这种地步的原因，总不外乎运气学说。人身是小天地，天地有这样的疠气，人就有这样的疫病，因为戊子年少阴君火司天，大运主事，五、六月间，又是少阴君火，加上少阳相火，小运主事，二之气与三之气共同行使职权，人身中只有一岁的气运，怎么能胜过烈火般的亢盛呢？医生不按照运气学说，固执于古方，百无一效。有的人有疑问来商量，他们便朗诵陈旧的言论，引用旧说来自我证明。总之，坚持用治疗伤寒的方法来治疗疫病，哪有不死人的呢？这些人的死，不是死于病，而是死于药，不是死于药，而是竟死于那些固执古方的医生的药。我根据运气学说，悟出疫病乃是胃受到外来淫热的侵袭，非用石膏不足以取得疗效！而且医者讲究意会，石膏属寒水，以寒胜热，以水克火，每每投药百发百中。五月间我也染上了疫病，凡是邀请我去诊治的，不能亲自诊视，询问症状，记录并传授方子，互相传送，救活了很多人。癸丑年京城多瘟疫，就连汪副宪、冯鸿胪也用我的方子互相传送，服用其他药无效的，都立刻痊愈。所以我把它写在书上，命名为清瘟败毒饮，随症状加减，详细列在后面，并附上治疗验证。
The pulse of epidemic rash (Yizhen) is invariably rapid (Shu). There are those that are floating, large, and rapid; those that are deep, fine, and rapid; those that are neither floating nor deep but rapid; and those that seem to appear and disappear when pressed. This is what the *Ling Shu* refers to as the manifestation of Yang toxin hiding and lying dormant. By examining the pulse, one can know the auspiciousness or inauspiciousness of the disease. If the pulse is floating, large, and rapid, the toxin is disseminating, representing a superficial heat syndrome in one meridian, and the illness will naturally resolve quickly. If the pulse is deep, fine, and rapid, the toxin has penetrated deeply; with large doses of clearing and resolving agents, it is still easy to subdue. As for pulses that seem to appear and disappear, or are completely hidden, the toxin is severe, and the symptoms are critical. Such pulses are occasionally seen at the onset of the disease but are quite common on the seventh or eighth day. Why? Because physicians initially mistake it for Cold Damage (Shanghan), heavily using diaphoretic (Fabiao) methods, which first depletes Yang Qi; when the exterior syndrome does not dissipate, they subsequently use purgatives, further depleting Yin fluids. Little do they know that if Cold Damage persists beyond the fifth or sixth day, the method should indeed be purgation, but one must carefully examine whether the pulse is forceful before applying it. Epidemic diseases are caused by pathogenic qi (Li Qi) that deviates from the four seasons. Pathogenic qi is an invisible toxin; those with deficient Stomach Qi contract it. The clinical presentation may resemble excess syndromes, yet the pulse is fine, rapid, and weak. To confront invisible pathogenic qi with the fierce potency of Rhubarb (Dahuang) and Mirabilite (Mangxiao), how could the evil toxin not enter through the deficiency? For those with weak constitutions, either Yang collapse or Yin collapse will occur; even those whose Qi and Blood can somewhat withstand it will inevitably see the pulse turn deep and hidden, with complications arising like swarms of bees: cold extremities, coma with delirious speech, oppression and dizziness with fixed gaze, enuresis, or involuntary stool discharge. In extreme cases, there is tongue retraction and testicular contraction, picking at bedclothes, and other various malignant symptoms that closely resemble Cold Damage. Physicians fail to realize that this is inviting evil inward, where extreme Yang resembles Yin, yet they claim it has transformed into a Yin syndrome, recklessly administering Ginseng (Renshen) and Cinnamon Twig (Guizhi). Patients die as if poisoned, turning blue-purple all over, with bleeding from the nose and mouth. For those who have not taken hot medicines, immediate administration of a large dose of Baidu Yin (Poison-Resolving Decoction) with heavy additions of Gypsum (Shigao) might possibly save them. Having saved many people in this manner, I record this for publication.
In the Wuzi year of the Qianlong reign, epidemic rash prevailed in my county. One person contracting the disease would infect the whole family. Among mild cases, eight or nine out of ten survived; among severe cases, only one or two out of ten survived. This pattern was generally observed throughout the region. At the onset, patients first experienced aversion to cold followed by fever, splitting headache, back pain as if beaten by a club, abdominal pain as if intestines were being twisted, accompanied by simultaneous vomiting and diarrhea. Adults and children suffered the same symptoms, following the same course in thousands of people. Some physicians treated it as a Three-Yang disease, others as a Two-Gan disease, and others as Cholera-like disorder (Huluan). By the second day, ominous signs arose in swarms, and various critical symptoms were too numerous to enumerate. Deaths resulting from such presentations were countless. This seasonal pathogenic qi is something people cannot avoid. The root cause lies in the theory of Five Movements and Six Qi (Yunqi). The human body is a microcosm; just as Heaven and Earth have such pathogenic qi, humans suffer corresponding epidemics. In the Wuzi year, Shaoyin Junhuo (Ministerial Fire) governed the Tian (Heavenly Qi), dominating the Great Movement. Between the fifth and sixth lunar months, Shaoyin Junhuo combined with Shaoyang Xianghuo (Ministerial Fire) to dominate the Small Movement. The Second Qi and Third Qi acted together in their functions. How could the single-year Qi of the human body withstand such rampant fire? Physicians who ignore Yunqi and rigidly adhere to ancient prescriptions achieve virtually no efficacy. When questioned, they recite old theories to justify themselves. Ultimately, persisting in treating epidemics with Cold Damage methods leads inevitably to death. These people do not die from the disease itself, but from medicine; not merely from medicine, but specifically from the prescriptions of physicians who rigidly cling to ancient formulas. Through understanding Yunqi, I realized that epidemic disease involves the Stomach suffering from exogenous excessive heat, which can only be effectively treated with Gypsum (Shigao)! Moreover, medical practice relies on intuitive understanding. Gypsum corresponds to Cold Water; using cold to overcome heat, and water to control fire, this approach yields consistent success. In May, I myself contracted the epidemic. For those who invited me for treatment, unable to visit personally, I inquired about symptoms, recorded prescriptions, and transmitted them mutually, saving many lives. In the Guichou year, epidemics were prevalent in the capital. Even Vice-Censor-in-Chief Wang and Herald Feng transmitted my prescriptions. Those who had failed with other medicines recovered instantly. Therefore, I wrote this down, naming the formula Qingwen Baidu Yin (Clear Plague and Resolve Toxin Decoction), with modifications based on symptoms, detailed below, along with case records.