发热者，热之发现于肌表者也。凡病多发热，热生于火，火本于气，（丹溪谓气有余
便是火，其义可见。）其理不外气乖与气郁二端。（小儿痘疹发热别见。）
一曰阳亢发热
阴阳水火，原自和平，不热不寒，是谓正气。一有乖违，不无偏胜。《经》曰∶
阳胜则热。此为亢阳之火，证见烦渴，燥结，小便赤涩，六脉洪数，治宜寒凉。
（有因浓酒浓味，蕴酿而成者，有炎令燥气，感触而致者，有五志过极，心火亢暴者。）
一曰阴虚发热（血虚同）
阴虚，谓肾水虚也。火性本上炎而外现，得水以制之，则离交于坎，龙潜于渊，
内蕴而为神明，下济而成交泰。若阴亏水虚，则柴干火烈，而焚灼为灾矣。（或由色欲
损精，或由泻利亡阴，或由燥热伤液，皆能致之也。）此之火炎，乃由水虚所致，与上条阳亢而阴
未亏者不同。证见口干体瘦，食少懒倦，头痛时作时止，遗精盗汗，骨蒸肉烁，唇
红颧赤，咳嗽痰血，久成痨瘵。治宜甘润之剂，滋水以制火。若误用苦寒，则火被
寒郁，其怒发愈烈矣。按薛立斋治一老人，肾虚火不归经，而游行于外，发热，烦
渴引饮，面目俱赤，遍舌生刺，敛缩如荔枝，两唇焦裂，或时喉间如烟火上
冲，急饮凉茶少解，两足心如烙，痰涎壅盛，小便频数，喘急，脉洪数无伦，而且
有力，扪其身烙手。以十全大补（见虚损）加山茱萸、泽泻、丹皮、山药、麦冬、五味、
附子，及八味丸（见虚损）治之而愈。愚谓此证明是水虚火炎，当用六味（见虚损），而用前药
者，必因其人年老，水火并虚故尔。如火不虚，不得因此案而误用温热，以致阴分
愈伤也。（虚不论水火，脉皆无力，而此有力者，必曾服寒凉之剂，激之使然。故凡用寒药直折者，必须热服，不
效、则药须用姜汁或酒炒过服之即愈。亦防郁遏之意也。再按此证，全似实火，然虚火较实火必反烈，以其离根浮
越，全体外现，比实火之内热透外，韬光埋焰者自不同也。《已任编》云∶有误服白虎，以致热甚如燔，冲开
三五尺，人不能近者，可想见虚火之烈矣）。血虚发热，或由吐衄便血，或由产后崩漏，一切失
血所致。证见烦躁，面目黑，渴饮不止。证类白虎，惟脉不长不实，浮大而重按全
无为异耳。误服白虎，必危。治宜滋阴补血。若阳并虚，兼用气药，血脱补气，阳生阴自长也。
一曰阳虚发热
阳虚，谓肾火虚也。阳虚应寒，何以反发热，则以虚而有寒，（若无寒而但阳虚，则止
自见其不足，不能发热）。寒在内而格阳于外，故外热；（阳被寒拒，出居肌表，外越则脱，不脱而又不能
内返，则格斗而激发为热也）。寒在下而戴阳于上，故上热也。此为无根之火，乃虚焰
耳。证见烦躁，欲坐卧泥水中，面赤如微酣，或两颧浅红，游移不定，（与实热之尽面通
红者异）。渴欲饮水，或咽喉痛，而索水置前，却不能饮，肌表虽大热，而重按之则不
热，或反觉冷，且两足必冷，小便清白，下利清谷，脉沉细，或浮数无力，按之欲
散。治宜温热之剂。温其中而阳内返，温其下而火归元。误投寒凉立死。（或口食冷物，
或鼻吸寒气，其人平素阳虚阴盛，外寒一中，阴邪遂张，真阳因之失守也。）
发热，是指热邪显现于肌表的症状。大多数疾病都会出现发热，热由火产生，而火根源于气。（朱丹溪认为“气有余便是火”，其道理可见一斑。）其机理不外乎“气乖”与“气郁”两个方面。（小儿痘疹引起的发热另见专论。）
第一种是阳亢发热。
阴阳、水火原本处于和平状态，不热不寒，这称为正气。一旦有了乖违，就不会没有偏胜。《黄帝内经》说：“阳胜则热。”这是亢盛的阳火，症状表现为烦躁口渴、大便燥结、小便赤涩，六脉洪大数急，治疗宜用寒凉之法。（有的因饮用浓酒、食用厚味，蕴酿而成；有的因感受炎热季节的燥气所致；有的因五志过极，导致心火亢盛暴烈。）
第二种是阴虚发热（血虚发热同理）。
阴虚，指的是肾水亏虚。火的性质本向上炎并外现，得到水的制约，就能实现离卦与坎卦相交（即心肾相交），如龙潜于深渊，在内蕴藏化为神明，在下济助达成交泰。如果阴液亏损、肾水不足，就像柴干火烈，从而焚灼成灾。（或者由于色欲过度损伤精血，或者由于腹泻痢疾亡失阴液，或者由于燥热伤及津液，都能导致这种情况。）这种火炎，是由于水虚所致，与上一条中阳亢而阴未亏损的情况不同。症状表现为口干体瘦、食欲减退懒倦、头痛时作时止、遗精盗汗、骨蒸潮热肌肉消瘦、嘴唇红颧骨赤、咳嗽痰中带血，久则形成痨瘵（肺结核类慢性消耗性疾病）。治疗宜用甘润的药物，滋补肾水以制约相火。如果误用苦寒药物，则火被寒气郁遏，其发作反而更加猛烈。按薛立斋治疗一位老人的案例：老人肾虚，火不归经，游行于体表，出现发热、烦躁口渴引饮、面目俱红、全舌生刺且收缩如荔枝状、双唇焦裂，有时感觉喉间有烟火上冲，急饮凉茶稍解，两足心如火烙，痰涎壅盛，小便频数，喘急，脉象洪数无伦次而且有力，触摸身体烫手。薛立斋使用十全大补汤（见虚损章节）加入山茱萸、泽泻、牡丹皮、山药、麦冬、五味子、附子，以及八味丸（见虚损章节）治愈了该病。我认为此证明确是水虚火炎，应当使用六味地黄丸（见虚损章节），而使用前述药物的原因，必然是因为此人年老，水火之气均虚的缘故。如果火不虚，绝不能因此案而误用温热药，以致阴分进一步受损。（无论是虚证不论水火，脉象通常都无力，但此例脉有力，必定是因为曾经服用过寒凉药物，激惹所致。所以凡是使用寒药直折火势的，必须热服，若无效，则药物需用姜汁或酒炒过后服用即可痊愈。这也是为了防止郁遏之意。再按此证，完全像实火，然而虚火比实火必然更猛烈，因为其离根浮越，全体外现，与实火之内热透外、韬光埋焰的情况自然不同。《已任编》记载：有误服白虎汤，导致热势炽盛如燃烧，热气冲出三五尺，人不能靠近的情况，可以想见虚火的猛烈了。）血虚发热，或者由于吐血、衄血、便血，或者由于产后崩漏，一切失血所致。症状表现为烦躁、面目发黑、渴饮不止。证候类似白虎汤证，只有脉象不长不实，浮大而重按全无作为区别。误服白虎汤，必然危险。治疗宜滋阴补血。如果阳气也虚，兼用补气药，所谓“血脱补气”，阳气生发则阴血自长。
第三种是阳虚发热。
阳虚，指的是肾火（命门之火）虚弱。阳虚应当畏寒，为什么反而发热？这是因为虚而有寒。（如果没有寒象而只是阳虚，则只表现出自身不足，不会发热。）寒邪在内格拒阳气于外，所以体表发热；（阳气被寒邪拒绝，外出居于肌表，向外浮越则会导致脱证，若不脱又不能内返，则发生格斗激发为热。）寒邪在下格拒阳气于上，所以上部发热。这是无根之火，乃是虚焰罢了。症状表现为烦躁，想要坐卧在泥水中，面色红如微醉，或两颧浅红，游移不定，（与实热之满面通红不同）。口渴想喝水，或咽喉痛，索要水放在面前，却不能喝，肌表虽然大热，但重按则不热，或反而觉得冷，且两脚必定冰冷，小便清白，下利清谷（完谷不化），脉象沉细，或浮数无力，重按欲散。治疗宜用温热药剂。温其中焦则阳气内返，温其下焦则火归元位。误投寒凉药会立即致死。（或者口食冷物，或鼻吸寒气，其人平素阳虚阴盛，外寒一侵，阴邪遂张，真阳因此失守。）
Fever refers to the manifestation of heat on the body surface. Most diseases involve fever; heat is generated by Fire (Huo), and Fire originates from Qi (vital energy). (Zhu Danxi stated that "excess of Qi constitutes Fire," illustrating this principle.) The underlying mechanism lies in two aspects: "Qi deviation" (Qi Guai) and "Qi stagnation." (Fever caused by smallpox/rash in infants is discussed separately.)
The first type is Hyperactive Yang Fever.
Yin, Yang, Water, and Fire are originally in harmony, neither hot nor cold, which is termed Righteous Qi (Zheng Qi). Once deviation occurs, there will inevitably be an excess of one side. The *Classic* states: "Yang excess leads to heat." This is hyperactive Yang Fire. Symptoms include irritability and thirst, dry constipation, dark and scanty urination, and a surging and rapid pulse in all six positions. Treatment should employ cooling methods. (Some cases arise from the accumulation caused by heavy wine consumption and rich foods; some result from contracting dryness during hot seasons; others stem from extreme emotional excess leading to hyperactive and violent Heart Fire.)
The second type is Yin Deficiency Fever (Blood Deficiency Fever is similar).
Yin deficiency refers to the depletion of Kidney Water. The nature of Fire is to flare upward and manifest externally; when restrained by Water, it achieves the interaction between Li (Fire trigram) and Kan (Water trigram), like a dragon hiding in the abyss, nurturing Spirit (Shen) internally and facilitating communication (Jiao Tai) downward. If Yin fluid is depleted and Kidney Water is insufficient, it is like dry firewood with intense flames, causing burning disaster. (This may be caused by excessive sexual activity damaging essence, diarrhea or dysentery losing Yin fluids, or dry-heat injuring body fluids.) This flaring fire is caused by water deficiency, differing from the previous category where Yang is hyperactive but Yin is not yet deficient. Symptoms include dry mouth, emaciation, poor appetite and lassitude, intermittent headache, seminal emission and night sweats, bone-steaming fever with muscle wasting, red lips and malar flush, coughing with blood-stained sputum, eventually developing into Lao Zhai (consumption/tuberculosis). Treatment should use sweet and moistening agents to nourish Water to control Fire. If bitter-cold herbs are mistakenly used, the Fire will be constrained by Cold, causing its eruption to become even more violent. According to a case treated by Xue Lizhai: An elderly patient suffered from Kidney deficiency with Fire failing to return to its source, wandering externally, presenting with fever, irritability, excessive thirst, red face and eyes, prickles covering the tongue which shrank like a lychee, cracked and scorched lips, sensation of smoke/fire rushing up the throat (relieved slightly by drinking cold tea), soles of feet feeling like iron plates, copious phlegm and saliva, frequent urination, wheezing and urgency, surging and rapid pulse without regularity but forceful, and a scorching body upon touch. Xue Lizhai treated him with Shiquan Dabu Decoction (see Deficiency Damage chapter) added with Cornus Fruit (Shanzhuyu), Alisma (Zexie), Moutan Bark (Danpi), Chinese Yam (Shanyao), Ophiopogon Root (Maidong), Schisandra Berry (Wuweizi), and Aconite Root (Fuzi), along with Bawei Wan (Eight-Ingredient Pill, see Deficiency Damage chapter), resulting in recovery. I believe this case clearly demonstrates Water deficiency with Fire flaring, for which Liuwei Dihuang Wan (Six-Ingredient Pill, see Deficiency Damage chapter) should have been used. The reason for using the aforementioned drugs was likely due to the patient's advanced age, indicating deficiency in both Water and Fire. If Fire were not deficient, one must not mistakenly use warming herbs based on this case, as it would further injure the Yin aspect. (In deficiency patterns, regardless of Water or Fire, the pulse is typically weak; however, the forcefulness here was likely provoked by previous administration of cold herbs. Therefore, when using cold herbs to directly subdue Fire, they must be taken warm. If ineffective, the herbs should be taken after being processed with ginger juice or wine fried, which leads to recovery. This also prevents constraint. Furthermore, this condition resembles Excess Fire, but Deficient Fire is often more violent than Excess Fire because it floats outward having lost its root, fully manifesting externally, unlike Excess Fire which has internal heat penetrating outward but hides its brilliance and flame. *Yiren Bian* records: There was a case of mistakenly taking Baihu Tang, leading to intense heat like burning, radiating three to five chi, making people unable to approach. This illustrates the violence of Deficient Fire.) Blood Deficiency Fever may result from hematemesis, epistaxis, melena, postpartum metrorrhagia, or any blood loss. Symptoms include irritability, dark complexion, and incessant thirst. The presentation resembles the Baihu Tang pattern, distinguished only by a pulse that is not long or solid, but floating, large, and empty upon deep pressure. Mistakenly administering Baihu Tang is dangerous. Treatment should focus on nourishing Yin and tonifying Blood. If Yang is also deficient, Qi-tonifying herbs should be added; "for blood loss, tonify Qi," as the generation of Yang promotes the growth of Yin.
The third type is Yang Deficiency Fever.
Yang deficiency refers to the weakness of Kidney Fire (Mingmen Fire). Yang deficiency should lead to cold intolerance; why does it present with fever? This is because there is deficiency accompanied by Cold. (If there were no cold signs and only Yang deficiency, it would merely show insufficiency without fever.) Cold inside repels Yang to the outside, causing external heat; (Yang is rejected by Cold, exits to the muscle layer, and if it floats outward without collapsing, yet cannot return inward, the struggle generates heat.) Cold below repels Yang to the top, causing upper heat. This is Rootless Fire, merely a false flame. Symptoms include irritability, a desire to sit or lie in mud/water, a flushed face resembling mild intoxication or shallow redness on the malar bones that shifts position (unlike the full-face redness of Excess Heat), thirst with desire to drink, or sore throat where water is requested but cannot be swallowed. Although the body surface is very hot, deep pressure reveals no heat or even coldness, and the feet are invariably cold. Urine is clear and profuse, stool contains undigested food (Qinggu), and the pulse is deep and fine, or floating and rapid but weak, dissolving upon pressure. Treatment should employ warming agents. Warming the Middle Jiao returns Yang inward; warming the Lower Jiao returns Fire to its origin. Mistakenly administering cold herbs leads to immediate death. (This may occur if one consumes cold food or inhales cold air; in individuals with pre-existing Yang deficiency and Yin excess, external cold invasion allows Yin pathogens to flourish, causing True Yang to lose its hold.)