世人论伤寒，辄曰阴证，而不知有三说也。有传经之阴证，阴中之热证也。有直中之阴
证，阴中之寒证也。有房室之阴证，阴中之虚证也。既犯房室而得热证，则灼热极甚；犯房
室而得寒证，则阴寒极甚。热之甚，清剂宜轻；寒之甚，温剂宜重。斯无弊耳，乃世人混称
夹阴，而医者漫不加察，反从而和之。噫，陋矣！
时疫之症，来路两条，去路三条，治法五条，尽矣。何谓来路两条？疫有在天者，有在
人者。如春应温而反寒，夏应热而反凉，秋应凉而反热，冬应寒而反温，非其时而有其气，
自人受之，皆从经络而入，或为头痛、发热、咳嗽，或为颈肿、发颐、大头天行之类，斯在
天之疫也。若夫一人之病，染及一室，一室之病，染及一乡，一乡之病，染及合邑，此乃病
气、秽气相传染，其气息俱从口鼻而入，其见症，憎寒壮热，胸膈满闷，口吐黄涎，乃在人之
疫以气相感，与天无涉。所谓来路两条者此也。
夫在天之疫，从经络而入，宜分寒、热，用辛温、辛凉之药以散邪，如香苏散、普济消
毒饮之类，俾其从经络入者仍从经络出也。在人之疫，从口鼻而入，宜用芳香之药以解秽，
如神术散、藿香正气散之类，俾其从口鼻入者仍从口鼻出也。至于经络、口鼻所受之邪，传
入脏腑，渐至潮热谵语，腹满胀痛，是为毒瓦斯归内，非疏通肠胃无由以解其毒，法当下之。
其大便自行者，则清之。下后而余热不尽者，亦清之，须令脏腑之邪从大便出也。所谓去路
三条者此也。
夫发散、解秽、清中、攻下，共四法耳，而谓治法有五，何也？大抵邪之所凑其气必虚
体虚受邪，必须以补法驾驭其间，始能收效万全，如气虚补气，血虚补血，古人所用参苏
饮、人参白虎汤、人参败毒散、黄龙汤、四顺清凉饮，方内有人参、当归，其意可想而知矣
于前四法中加以补法，乃能左右咸宜，纵横如意，邪气退而元气安、所谓治法五条者此也。
熟此五法，而融会贯通，其于治疫也，何难之有？
世人谈论伤寒，往往统称为阴证，却不知其中包含三种说法。有一种是传经的阴证，属于阴经中的热证；有一种是直中的阴证，属于阴经中的寒证；还有一种是房劳所致的阴证，属于阴经中的虚证。如果因房事不节而患得热证，则体内灼热极甚；若因房事不节而患得寒证，则体内阴寒极甚。热势极盛时，清热剂（清剂）的药量宜轻；寒势极盛时，温里剂（温剂）的药量宜重。这样处理就没有弊病了。然而世人混淆称之为“夹阴”（指外感病兼有肾虚或房劳损伤），医生们随意不加审察，反而用调和之法治疗。唉，这也太浅陋了！
时行疫病（时疫）的症状，发病途径有两条，转归出路有三条，治疗方法有五种，这就概括完整了。什么叫发病途径两条？疫病有的来自自然界气候异常（在天），有的来自人与人之间的传染（在人）。比如春天本该温暖却反而寒冷，夏天本该炎热却反而凉爽，秋天本该凉爽却反而炎热，冬天本该寒冷却反而温暖，这种非其时而有其气的情况，人体感受后，邪气都从经络进入，症状表现为头痛、发热、咳嗽，或者颈肿、发颐（腮腺炎类疾病）、大头瘟（大头天行）之类，这就是来自自然界的疫病。如果是某一个人患病，传染给整个房间的人，整个房间的人患病，传染给整个乡村，整个乡村的人患病，传染到全县，这是病气和秽气相互传染，气息都从口鼻进入，出现的症状有憎寒壮热（极度恶寒伴高热）、胸膈满闷、口吐黄涎，这是人与人之间通过气息感应传染的疫病，与自然界气候无关。所谓发病途径两条，就是指这个意思。
对于来自自然界气候异常的疫病，邪气从经络进入，应当分辨寒热，使用辛温或辛凉的药物来疏散邪气，如香苏散、普济消毒饮之类的方剂，使从经络进入的邪气仍从经络排出。对于人与人传染的疫病，邪气从口鼻进入，应当使用芳香的药物来化解秽浊之气，如神术散、藿香正气散之类的方剂，使从口鼻进入的邪气仍从口鼻排出。至于从经络和口鼻侵入的邪气，传入脏腑，逐渐发展到潮热谵语（定时发热说胡话）、腹部胀满疼痛，这是毒瓦斯内陷，如果不疏通肠胃就无法解除毒素，治法必须采用下法（泻下）。如果大便自行通畅的，则采用清法（清热）。攻下之后余热未尽的，也采用清法，必须让脏腑的邪气随大便排出。所谓转归出路三条，就是指这个意思。
发散、解秽、清热、攻下，总共只有四种方法，为什么说治疗方法有五种呢？大抵邪气聚集的地方，正气必然虚弱。体质虚弱而感受邪气，必须在治疗中配合补法来驾驭病情，才能收到万全的效果，比如气虚就补气，血虚就补血，古人所用的参苏饮、人参白虎汤、人参败毒散、黄龙汤、四顺清凉饮等方剂中有人参、当归，其中的用意可想而知。在前四种方法中加入补法，才能左右逢源，运用自如，使邪气退去而元气安定。所谓治疗方法五种，就是指这个意思。熟习这五种方法，并融会贯通，那么治疗疫病又有什么困难呢？
When discussing Shanghan (Cold Damage), people generally refer to it as Yin Syndrome, without realizing that there are three distinct categories. There is the Yin Syndrome of transmission through meridians, which is a Heat Syndrome within the Yin aspect; there is the Yin Syndrome of direct invasion, which is a Cold Syndrome within the Yin aspect; and there is the Yin Syndrome resulting from sexual indiscretion, which is a Deficiency Syndrome within the Yin aspect. If one contracts a Heat Syndrome due to sexual indiscretion, the internal burning heat will be extreme; if one contracts a Cold Syndrome due to sexual indiscretion, the internal Yin-Cold will be extreme. When the heat is extreme, Qingji (Clearing Agents) should be used lightly; when the cold is extreme, Wenji (Warming Agents) should be used heavily. This approach avoids弊端 (drawbacks). However, people indiscriminately label these conditions as Jia Yin (Clasped Yin, referring to external contraction complicated by Kidney deficiency or sexual injury), and physicians, acting arbitrarily without careful examination, instead apply harmonizing methods. Alas, how superficial this is!
The manifestations of Shiyi (Seasonal Epidemic Diseases) have two origins, three pathways of resolution, and five treatment methods, which comprehensively cover the subject. What are the two origins? Epidemics originate either from celestial factors (Tian Zai) or human factors (Ren Zai). For instance, if spring should be warm but turns cold, summer should be hot but turns cool, autumn should be cool but turns hot, or winter should be cold but turns warm, such abnormal Qi occurring out of season enters the human body via the meridians. Symptoms may include headache, fever, cough, neck swelling, Fayi (mumps-like swelling), or Datou Tianxing (Big Head Plague); this constitutes an epidemic from celestial factors. Conversely, if one person’s illness infects a room, a room’s illness infects a village, and a village’s illness infects a county, this results from the transmission of Pathogenic Qi and Filthy Qi. The pathogenic air enters through the mouth and nose, presenting with aversion to cold accompanied by high fever, chest and epigastric fullness and oppression, and vomiting of yellow saliva. This is an epidemic transmitted between humans through Qi resonance, unrelated to celestial factors. These constitute the two origins.
For epidemics originating from celestial factors, where pathogens enter via the meridians, one must differentiate between Cold and Heat and use Xinwen (Acrid-Warm) or Xinliang (Acrid-Cool) herbs to disperse the pathogen, such as Xiangsu San or Puji Xiaodu Yin, allowing pathogens entering via meridians to exit via meridians. For epidemics transmitted between humans, where pathogens enter via the mouth and nose, one should use aromatic herbs to resolve filth, such as Shenzhu San or Huoxiang Zhengqi San, allowing pathogens entering via the mouth and nose to exit via the mouth and nose. As for pathogens invading the Zang-Fu organs from the meridians and mouth/nose, progressing to tidal fever and delirious speech, abdominal fullness and pain, this indicates that toxic vapors have moved inward. Without unblocking the intestines and stomach, the toxin cannot be resolved; thus, the treatment method must employ Xiàfǎ (Purgative Method). If bowel movements occur spontaneously, then Qīngfǎ (Clearing Method) is used. If residual heat remains after purgation, Qīngfǎ is also employed, ensuring that Zang-Fu pathogens exit via the stool. These constitute the three pathways of resolution.
Dispersing, resolving filth, clearing heat, and purging constitute four methods. Why are there said to be five treatment methods? Generally, where pathogenic Qi gathers, Healthy Qi (Zheng Qi) must be deficient. When a constitutionally weak individual contracts pathogens, Bu Fa (Tonification Method) must be integrated into the treatment strategy to ensure complete efficacy. For example, tonifying Qi for Qi deficiency and nourishing Blood for Blood deficiency. In ancient formulas such as Renshen Su Yin, Renshen Baihu Tang, Renshen Baidu San, Huanglong Tang, and Sishun Qingliang Yin, the inclusion of Renshen (Ginseng Radix et Rhizoma) and Danggui (Angelicae Sinensis Radix) reveals their intent. By adding tonification to the previous four methods, one can maneuver flexibly, causing pathogenic Qi to retreat while stabilizing Yuan Qi. These constitute the five treatment methods. Once these five methods are mastered and thoroughly integrated, what difficulty could there possibly be in treating epidemics?