疫邪见证，千变万化，然总不出表里二者。但表证中有里邪，里证中有表邪，则又不可不细察也。故列证分表
里以尽其常，又细辨以尽其变，使人人临证，胸有定见，少救横夭于万一耳。
时疫发热与风寒杂证同，其发热时，气、色、神、脉、舌苔则不同。辨得为时疫发热，又当知有浅、深、
表、里之异，不辨无以施治。发热表证居多，亦有里证发热，半表半里发热，余邪不尽复出于表发热，邪退正
虚发热。
而表证发热，脉不浮、不沉而数，寸大于关尺，热在皮肤，扪之烙手，久按反轻，必兼头痛、项强、腰痛、胫
酸，或头面、身体、皮肤有红肿疼痛。诸证不必全现，有一于此，便是表证发热，九味羌活汤、人参败毒散、六神
通解散选用。冬月严寒及恶寒甚者，大青龙汤、葳蕤汤、越婢汤、阳旦汤可借用。全不恶寒者，白虎汤、黄芩汤可
加减用。
里证发热，脉或滑，或沉数，或洪滑，关尺盛于寸，热必在肌肉、筋骨，初扪热轻，久按热甚，必兼烦渴，胸
腹满，大便或不通，或自利，或便血及脓，小便黄赤，或谵妄、狂昏。诸证虽不必全现，必兼二、三证方是里证发
热，栀子豉汤、黄连解毒汤、小陷胸汤、三承气汤、导赤散、泻心汤、猪苓汤、天水散选用。
半表半里发热，脉多弦，胸胁满，或热或止，或口苦
咽干，目眩耳聋，或目赤，或喜呕心烦，或兼见表里证，达原饮、柴葛解肌汤、小柴胡汤选用。
时疫发热时，用药最要清楚，此处头绪不差，后传变多危，救援亦易，不然难于收拾矣。凡见发热，即当辨其
气、色、神、脉、舌苔，为风寒，为时疫。系时疫，又当辨在表、在里、在半表半里。然时疫见证，纯表纯里者
少，表里夹杂者多。表里夹杂，吴氏达原饮为主。表证多，加羌活；里证多，加大黄；半表半里证多，加柴胡、
葛根、淡豉；或表里证均见，则诸药全用，即三消饮取效最多，诚时疫主剂。
至已愈数日而复发热者，乃募原伏有不尽之邪，复出于表，当察其证之表里多寡，以前法治之。大抵愈后复
发，则里热多而表热少，虽有当用表药之证，不过葛根、柴胡、淡豉而已，无更用羌活之理。若愈后另受风寒，发
热、无汗、舌上无苔者，不在此例。时疫愈后复热、无
汗，重用葛根五钱最妙，以其性凉而解肌发汗，既不碍无汗之表，又不碍烦热之里。
更有平素虚损，或老人，或大病后复染时疫，屡经汗、下、清解，其热转甚，或全无表、里实证，或六脉豁
豁然空，或较初起洪滑更甚，或用表药而身痛更甚，或屡用清热药而烦躁、昏沉更甚，或屡用下药而舌
燥更甚，此皆邪退正虚之发热也。王太仆所谓∶大虚有盛候，反泻含
冤也。此时须略去证状，而消息阴阳、虚实。阴虚则热渴、枯竭之证多，责在肾，宜六味地黄汤；兼气虚，合生
脉散，须大作汤液，昼夜频进效始捷。阳虚则呕利、悸眩之证多，责在脾，宜六君子汤；兼血虚，归脾汤、参胡三
白散、清燥汤选用。若遇此等证，仍用汗、下、凉解、宣伐，断无生理矣。
又发热之为表、为里、为半表半里、为复、为虚，证状明显有据者，自易施治。若脉证夹杂模糊，难于分辨
者，须以舌苔为据。初起舌苔薄白，或无苔而润，属在表。白苔而浓，或兼微黄，或中黄边白，中黄尖白，或
二、三色，属在半表半里。黄苔、酱色苔、黑苔属里。舌苔燥则不论何色皆属里证。屡经汗、下后，舌苔润而发热
者，属阳虚；无苔而燥者，属阴虚。发热之表、里、虚、实，根据此辨之，思过半矣。惟虚证发热有似实证，即舌苔
亦难凭据，又当从病之来路探讨。若屡经汗、下、宣伐而热愈甚者，从虚治无疑。或虽经汗、下而热渐减，药有效
则仍属余邪未尽，不可遽补致邪热复壅，夭人年寿。似此虚实关头，不可不细心体认也。
以上辨表里虚实诸法，虽指发热时言，然类而推之，凡证皆可根据此为辨，惟在学人之善悟耳。
疫邪所表现出的证候，千变万化，但总归不出表证和里证两类。然而，表证中可能夹杂里邪，里证中也可能夹杂表邪，这就不可不仔细辨别了。因此，列出证候分为表、里以概括其常规情况，又通过细致辨析以穷尽其变化，使每个人在临证时心中都有确定的见解，从而能在万一之中挽救那些因误治而横死或早夭的患者。
时行疫病引起的发热与风寒类杂病引起的发热相似，但在发热时，患者的气色、神态、脉象、舌苔则有所不同。辨别出是时行疫病引起的发热后，又应当知道有浅深、表里的区别，不加以辨别就无法实施治疗。发热属于表证的居多，也有属于里证发热的，有半表半里发热的，有余邪未尽再次出于体表而发热的，还有邪气退去后正气虚弱引起的发热。
如果是表证发热，脉象不浮也不沉而是数脉，寸口脉大于关部和尺部，热感在皮肤表面，触摸时感觉烫手，但久按反而感觉热度减轻，必定兼有头痛、项背强直、腰痛、小腿酸痛，或者头面、身体、皮肤出现红肿疼痛。这些症状不必全部出现，只要具备其中一项，就是表证发热，可选用九味羌活汤、人参败毒散、六神通解散。冬季严寒以及恶寒严重的，可借用大青龙汤、葳蕤汤、越婢汤、阳旦汤。完全不怕冷的，可加减使用白虎汤、黄芩汤。
如果是里证发热，脉象或滑，或沉数，或洪滑，关部和尺部脉盛于寸部，热感一定在肌肉、筋骨深处，初触时热度较轻，久按时热度更甚，必定兼有烦躁口渴，胸腹部胀满，大便或者不通畅，或者自行泄泻，或者便血及脓，小便黄赤，或者胡言乱语、狂乱昏沉。这些症状虽然不必全部出现，但必须兼有两三个症状才是里证发热，可选用栀子豉汤、黄连解毒汤、小陷胸汤、三承气汤、导赤散、泻心汤、猪苓汤、天水散。
半表半里发热，脉象多呈弦脉，胸胁部胀满，或者发热或者停止，或者口苦咽干，头晕目眩耳聋，或者眼睛发红，或者喜欢呕吐心烦，或者兼见表证和里证的症状，可选用达原饮、柴葛解肌汤、小柴胡汤。
患时行疫病发热时，用药最要紧的是思路清晰，此处头绪不乱，后续传变就会少且危重程度低，救援也容易；否则就难以收拾了。凡是见到发热，就应当辨别其气、色、神、脉、舌苔，判断是风寒还是时行疫病。如果是时行疫病，又应当辨别是在表、在里、还是在半表半里。然而时行疫病的证候，纯表证或纯里证的情况较少，表里夹杂的情况较多。对于表里夹杂的证候，以吴氏达原饮为主方。如果表证多，加羌活；里证多，加大黄；半表半里证多，加柴胡、葛根、淡豆豉；或者表里证都见到，则诸药全用，即三消饮，取效最多，确实是治疗时行疫病的主方。
至于已经痊愈几天后又发热的，这是募原（膜原）潜伏的余邪未尽，再次出于体表，应当观察其证候中表里所占的比例多少，用前面的方法治疗。大致痊愈后复发，则是里热多而表热少，虽然有应当使用解表药的情况，也不过是用葛根、柴胡、淡豆豉罢了，没有再用羌活的道理。如果是痊愈后另外感受风寒，出现发热、无汗、舌上没有舌苔的情况，不在此例。时行疫病痊愈后再次发热、无汗，重用五钱葛根最为巧妙，因为葛根性凉能解肌发汗，既不影响无汗的表证，又不妨碍烦热的里证。
更有平时体质虚损，或者是老年人，或者是大病之后又感染时行疫病，经过多次发汗、攻下、清热解表治疗后，发热反而加重，或者完全没有表证、里证的实证表现，或者六脉豁然空虚，或者比初起时的洪滑脉更严重，或者使用解表药后身体疼痛更严重，或者多次使用清热药后烦躁、昏沉更严重，或者多次使用攻下药后舌燥更严重，这些都是邪气退去后正气虚弱引起的发热。王太仆所说的：“大虚之证会有盛实的假象，如果错误地采用泻法，患者将含冤而死。”此时必须略去表面的证状，而斟酌阴阳、虚实的本质。阴虚则热渴、枯竭的症状多，病责在于肾，宜用六味地黄汤；兼有气虚，合用生脉散，必须大量煎煮汤剂，昼夜频繁服用才能见效快。阳虚则呕吐泄泻、心悸眩晕的症状多，病责在于脾，宜用六君子汤；兼有血虚，可选用归脾汤、参胡三白散、清燥汤。如果遇到这类证候，仍然使用发汗、攻下、凉解、宣伐的方法，绝对没有生机了。
另外，发热表现为表证、里证、半表半里证、复发、虚证，如果证状明显有据的，自然容易施治。如果脉象和证状夹杂模糊，难以分辨的，必须以舌苔为依据。初起时舌苔薄白，或者无苔而湿润，属于在表。白苔而浓厚，或者兼微黄，或者中间黄边缘白，中间黄尖端白，或者二、三种颜色混合，属于在半表半里。黄苔、酱色苔、黑苔属于里证。舌苔干燥则不论什么颜色都属于里证。经过多次发汗、攻下后，舌苔湿润而发热的，属于阳虚；无苔而干燥的，属于阴虚。根据这一点来辨别发热的表、里、虚、实，思虑就已经过半了。只有虚证发热类似实证，即使舌苔也难以作为依据，又应当从疾病的来路进行探讨。如果经过多次发汗、攻下、宣伐后发热反而更严重的，毫无疑问要从虚证治疗。或者虽然经过发汗、攻下但发热逐渐减轻，药物有效，则仍属于余邪未尽，不能急于进补导致邪热再次壅滞，折损人的寿命。像这种虚实的关键关头，不可不细心体察认识。
以上辨别表里虚实的各种方法，虽然是针对发热而言，但类推开来，凡是有证候都可以据此进行辨别，只在于学习中医的人善于领悟罢了。
The manifestations of epidemic pathogens are myriad and ever-changing, yet they ultimately do not go beyond the categories of Exterior (Biao) and Interior (Li). However, when Exterior patterns contain Interior pathogens, or Interior patterns contain Exterior pathogens, careful differentiation is indispensable. Therefore, listing patterns by distinguishing between Exterior and Interior covers their regularities, while detailed differentiation exhausts their variations, enabling practitioners to maintain clear judgment during clinical practice and thereby save lives from premature death in rare instances.
The fever caused by seasonal epidemics resembles that of wind-cold miscellaneous diseases; however, during fever, differences exist in Qi (vital energy), complexion, spirit, pulse, and tongue coating. Once identified as epidemic fever, one must further recognize distinctions in depth (shallow/deep) and location (Exterior/Interior); without such differentiation, treatment cannot be administered. Most fevers belong to the Exterior pattern, but there are also fevers belonging to the Interior pattern, half-Exterior half-Interior pattern, fevers arising from residual pathogens re-emerging at the Exterior after partial retreat, and fevers resulting from deficiency of healthy Qi after pathogenic factors have receded.
In cases of Exterior pattern fever, the pulse is neither floating nor deep but rapid; the Cun (inch) position is stronger than the Guan (bar) and Chi (cubit) positions; the heat sensation is superficial on the skin, feeling scalding to the touch initially but diminishing upon prolonged pressure; it is invariably accompanied by headache, stiffness of the neck and back, lower back pain, soreness of the shins, or redness, swelling, and pain in the head, face, body, or skin. These symptoms need not all appear simultaneously; the presence of any one indicates Exterior pattern fever. Formulas such as Jiuwei Qianghuo Decoction (Nine-Ingredient Notopterygium Decoction), Renshen Baidu San (Ginseng Detoxification Powder), or Liushen Tongjie San may be selected. In severe winter cold or cases with significant aversion to cold, Da Qinglong Tang (Major Blue-Green Dragon Decoction), Weirui Tang (Asparagus Decoction), Yebibo Tang (Yi Ma Decoction), or Yangdan Tang may be borrowed. In cases with no aversion to cold at all, Baihu Tang (White Tiger Decoction) or Huangqin Tang (Scutellaria Decoction) may be used with modifications.
In cases of Interior pattern fever, the pulse may be slippery, deep-rapid, or surging-slippery; the Guan and Chi positions are stronger than the Cun position; the heat sensation is located deep within muscles and bones, feeling mild upon initial touch but intense upon prolonged pressure; it is invariably accompanied by irritability and thirst, chest and abdominal fullness, constipation or spontaneous diarrhea, bloody or purulent stools, yellow-red urine, or delirium and manic stupor. Although these symptoms need not all appear, the presence of two or three confirms Interior pattern fever. Formulas such as Zhizi Chihui Tang (Gardenia and Soybean Fermented Decoction), Huanglian Jiedu Tang (Coptis Detoxification Decoction), Xiao Xiantong Tang (Minor Trapped Phlegm Decoction), Three Chengqi Decoctions (Three Bowel-Unblocking Decoctions), Daochi San (Guide Out Redness Powder), Xiexin Tang (Drain Epigastrium Decoction), Zhuling Tang (Polyporus Decoction), or Tianshui San may be selected.
In half-Exterior half-Interior fever, the pulse is often wiry; there is chest and hypochondriac fullness; fever may come and go; symptoms may include bitter taste in the mouth, dry throat, vertigo, deafness, red eyes, nausea, or irritability; or it may present with mixed Exterior and Interior signs. Darao Yin (Reach the Origin Infusion), Chaige Jieji Tang (Bupleurum and Kudzu Muscle-Releasing Decoction), or Xiaochaihu Tang (Minor Bupleurum Decoction) may be selected.
When treating fever caused by seasonal epidemics, clarity in medication strategy is paramount. If the initial approach is correct, subsequent transmission will be less critical and rescue easier; otherwise, the situation becomes difficult to manage. Upon observing fever, one must differentiate based on Qi, complexion, spirit, pulse, and tongue coating to determine if it is wind-cold or seasonal epidemic. If it is a seasonal epidemic, one must distinguish whether it is in the Exterior, Interior, or half-Exterior half-Interior. However, pure Exterior or pure Interior patterns are rare in epidemics; mixed Exterior-Interior patterns are common. For mixed patterns, Wu’s Darao Yin (Reach the Origin Infusion) is the primary formula. If Exterior signs predominate, add Qianghuo (Notopterygii Rhizoma et Radix); if Interior signs predominate, add Dahuang (Rhei Radix et Rhizoma); if half-Exterior half-Interior signs predominate, add Chaihu (Bupleuri Radix), Gegen (Puerariae Lobatae Radix), and Danshi (Sojae Semen Praeparatum); if both Exterior and Interior signs are present, use all herbs together, i.e., Sanxiao Yin (Three Eliminations Infusion), which yields the best results and serves as the principal formula for seasonal epidemics.
If fever recurs several days after recovery, it indicates residual pathogens lurking in the Mu Yuan (Membrane Source) re-emerging at the Exterior. One should assess the proportion of Exterior versus Interior signs and apply previous methods. Generally, post-recovery recurrence implies more Interior heat than Exterior heat; even if Exterior-releasing herbs are indicated, only Gegen (Puerariae Lobatae Radix), Chaihu (Bupleuri Radix), and Danshi (Sojae Semen Praeparatum) are appropriate, not Qianghuo (Notopterygii Rhizoma et Radix). This does not apply if the patient contracts new wind-cold after recovery, presenting with fever, anhidrosis, and a tongue lacking coating. For post-epidemic fever with anhidrosis, using a heavy dose (5 qian) of Gegen (Puerariae Lobatae Radix) is optimal because its cool nature releases the muscle layer and induces sweating without obstructing the Exterior (due to anhidrosis) or aggravating the Interior (due to irritative heat).
In patients with chronic deficiency, the elderly, or those contracting seasonal epidemics after severe illness, where repeated sweating, purging, and clearing treatments lead to intensified fever, or absence of solid Exterior/Interior signs, or hollow pulses (Huohuo Kong), or pulses more surging/slippery than at onset, or worsening body pain with Exterior-releasing herbs, or increased irritability/stupor with cooling herbs, or increased dry tongue with purgatives, these are fevers due to Healthy Qi deficiency after pathogen retreat. As Wang Taipu stated: "Great deficiency presents with excessive symptoms; wrongly applying purgation brings injustice." At this stage, one must disregard superficial symptoms and deliberate on Yin/Yang and Deficiency/Excess. Yin deficiency manifests as heat-thirst and exhaustion, rooted in the Kidney, treated with Liuwei Dihuang Wan (Six-Ingredient Rehmannia Pill); if combined with Qi deficiency, integrate Shengmai San (Generate Pulse Powder), prepared as strong decoctions taken frequently day and night for swift effect. Yang deficiency manifests as vomiting/diarrhea and palpitations/dizziness, rooted in the Spleen, treated with Liujunzi Tang (Six Gentlemen Decoction); if combined with Blood deficiency, select Guipi Tang (Spleen-Restoring Decoction), Canhu Sanbai San (Ginseng, Bupleurum, and Three Whites Powder), or Qingzao Tang (Clear Dryness Decoction). If such conditions are still treated with sweating, purging, cooling, or dispersing methods, survival is impossible.
Furthermore, when fever clearly presents as Exterior, Interior, half-Exterior half-Interior, recurrent, or deficient, treatment is easy. If pulse and symptoms are mixed and obscure, tongue coating becomes the key diagnostic basis. Initial thin white coating or moist coating without苔 indicates Exterior. Thick white coating, or slightly yellow, or yellow center with white edges/tip, or mixed colors, indicates half-Exterior half-Interior. Yellow, sauce-colored, or black coatings indicate Interior. A dry coating, regardless of color, indicates Interior. After repeated sweating/purging, a moist coating with fever indicates Yang deficiency; a coating-less dry tongue indicates Yin deficiency. Differentiating Exterior/Interior/Deficiency/Excess via these signs resolves most of the diagnostic challenge. However, Deficient fever mimicking Excess makes tongue diagnosis unreliable; one must trace the disease's progression. If fever worsens after repeated sweating/purging/dispersing, treat as Deficiency. If fever gradually decreases after sweating/purging, indicating efficacy, it remains residual pathogen; do not tonify hastily to avoid trapping heat and shortening life. Such critical junctures between Deficiency and Excess require careful discernment.
Although the above methods for differentiating Exterior/Interior/Deficiency/Excess focus on fever, they can be extrapolated to all patterns, depending on the practitioner's aptitude.