南方之地。寒暑不时。春夏淫雨则多寒。晨夕雾昏。地下湿蒸。故阴湿之气常盛。秋冬久晴则多
热。草木不凋而放花。故阳燠之气恒泄。昼燠。夜寒。晴霁热。阴雨寒。人居其中。因寒湿之气盛。
故下体重湿。生痰又多。痰因秋冬热故。热多上壅。肤多出汗。至腠理不密。阳外而阴内。阳浮而阴闭。
于斯时也。若饮食失度。起居不时。及食生冷食炙 。则痰与食相并积于胃。而寒热之病作矣。或不
避暑。奔走于日中。或避暑而坐卧当风。闭其汗孔。使汗不出。此病亦因之而作。或因其晨多雾而寒。
饮酒以御之。少焉日出。而热。则酒与痰相并滞于膈上。此病亦因之而作。或晨寒而少衣。或夜冷而
薄衾。则寒与痰相并。亦
作寒热。或因晨寒多衣。行至日中未解。则暑与痰相并。亦作寒热。要之此病之本。本于天气
热元阳恒泄。在人之阳气。自不降而内又多痰。再不能调摄。感于不正之气。宜其病有上热下寒
之症。所谓无痰不成疟者是也。养生者能远房室。省劳役。毋食生冷。毋食炙 。毋醉早酒。毋
饱晚饭。毋乘暑行走。毋当风坐卧。一日之中。顺其寒暑。而加减衣裳。则瘴虽毒。庶可免矣。
外伤寒邪之症与瘴疟。俱有寒热。医者尽以瘴疟作伤寒。率用汗吐下之法治之。其枉死者。
不可胜计。由其不辨寒热症候耳。今细分之。经曰。冬伤于寒。春必病瘟。冬若即病。谓之伤寒。
不即病至春变为瘟病。至夏变为热病。其病也。多自太阳经始。故发热恶寒。头痛脊强无汗。口中
和而不恶。食脉浮紧。为伤寒。或恶风自汗。而脉浮缓。为伤风。其热无退时。若传经或传阳明经。则有
目痛鼻干不得眠脉长之症。或传少阳经。则有耳聋胁痛。口苦呕吐。舌白苔脉弦之症。若传阳明
腑病为入里。舌苔黄口渴。心烦舌干。不恶寒反恶热。扬掷手足。揭去衣被。狂言谵语。脉洪数
内实之证。宜用下剂。下迟则入阴经。方舌黑大。凡伤寒之热。全不间断。直至传入里。下后方
罢。经曰。夏伤于暑。秋必 疟。夏暑汗不出。秋成风疟。是知疟之发。多因于暑。故发瘴之地。
四时常似夏。其病也无传经。若是冷瘴。则有恶寒发热。头痛脚弱腰重。口中不和。呕吐或不呕吐。
脉弦带数。一呼一吸。脉来六至。或七至八至。或先寒后热。或先热后寒。方其寒也。脉则沉迟
而伏。及其热也。脉则六至七至。而弦洪渴欲饮水。饮则多吐。揭去衣被。待其汗出。热则退矣。或
无汗而热久亦退。或间日再发。或一日一发。此为轻症。若是热瘴。则不恶寒惟发热壮热。头痛身
倦。腰重脚弱烦躁。胸膈不利。呕逆或不呕逆。自利或不自利。小便赤涩。口渴脉洪弦七
至八至。热亦不间断。一日二日舌便黑。目红面赤。渴欲饮冷。与之水亦能饮。狂言谵语。或大便闭。
至日晡尤甚。与伤寒下症无异。细察之。身中之热有不热处。以手扪之。额上极热。面微热黄尖凉。
心胸及腹极热。背微热。腰以下不甚热。重者常冷。或厥且谵语。以手扪心胸。蜷卧狂起。则脚重
无力何也。瘴病是上热下寒。故腰以下。不热而沉重。上身之症。虽阳而阴。症隐具于其中。鼻尖
为年寿宫。年寿属脾。脾寒所以鼻尖凉。此病是外热内寒。热症虽见于外。而内寒之症。验于鼻凉。
蜷卧叉手。胃胸隐然见矣。或谓是伤寒阴症。似阳亦非是。若阴症似阳。渴欲饮冷。与之冷则不饮。
瘴病与之则能饮。若用药得宜则热退。或得间日热。退时则脉微弱。非复前之洪弦数矣。大抵瘴
与伤寒大不相同。伤寒因于寒。瘴病因于暑。伤寒有传经。有变症。有传染。而瘴病不传经。无变症。
不传染。若医者误认恶寒发热为表症。用伤寒汗药。以狂言谵语。大便秘舌黑为里症。用伤寒下药。则不旋踵而告变矣。
南方地区，寒暑变化无常。春夏季节淫雨连绵，则寒气偏盛；早晚雾气昏暗，地下湿气蒸腾，因此阴湿之气常常旺盛。秋冬季节久晴无雨，则热气偏盛，草木不凋谢反而开花，因此阳热之气经常外泄。白天炎热，夜晚寒冷；晴天炎热，阴雨寒冷。人居住在这样的环境中，因为寒湿之气盛行，所以下半身身体沉重且潮湿，生痰也多。痰的产生是因为秋冬季节的热气，热气多向上壅滞。皮肤容易出汗，导致腠理（皮肤纹理及汗孔）不致密，阳气浮越于外而阴气闭郁于内，阳气浮散而阴气闭塞。在这个时候，如果饮食没有节制，起居没有规律，以及食用生冷食物或烤炙燥热之物，那么痰与食积就会相互搏结停滞在胃中，于是寒热交替的疾病就发作了。或者不避暑热，在烈日下奔走；或者避暑时坐卧当风，关闭了汗孔，使汗水无法排出，这种病也会因此发作。或者因为早晨多雾而感到寒冷，饮酒来抵御它，过了一会儿太阳出来，天气变热，那么酒与痰就会相互搏结停滞在膈上，这种病也会因此发作。或者早晨寒冷却穿得少，或者夜晚寒冷却盖得薄，那么寒邪与痰浊相互搏结，也会引发寒热症状。或者因为早晨寒冷而穿得多，走到中午还没有脱下，那么暑邪与痰浊相互搏结，也会引发寒热症状。总之，这种病的根本，在于天气炎热，元气中的阳气经常外泄，人体自身的阳气不能下降，体内又多痰浊，再加上不能调养摄护，感受了不正之气，理应出现上热下寒的症状。所谓“无痰不成疟”说的就是这种情况。善于养生的人如果能远离房事，减少劳役，不吃生冷食物，不吃烤炙燥热之物，不醉酒早饮，晚饭不吃得过饱，不顶着暑热行走，不坐在风口或卧在风中，一天之中顺应寒暑变化而增减衣裳，那么即使瘴气有毒，也差不多可以避免了。
外伤寒邪的症状与瘴疟，都有寒热表现。医生们全都把瘴疟当作伤寒治疗，一律使用发汗、催吐、攻下的方法去治疗，那些被误治致死的人，数不胜数。这是因为他们不辨别寒热的症候罢了。现在详细区分它们。医经说：冬天感受寒邪，春天必定发生温病。如果冬天感受寒邪随即发病，称为伤寒。如果不随即发病，到了春天变为温病，到了夏天变为热病。这类疾病，大多从太阳经开始。所以出现发热、恶寒、头痛、脊背强直、无汗、口中平和而不苦、食欲正常、脉象浮紧等症状，这是伤寒。或者出现怕风、自汗、脉象浮缓等症状，这是伤风。其热势不退的时候，如果传经或者传入阳明经，就会出现眼睛疼痛、鼻子干燥、不得安眠、脉象长等症。或者传入少阳经，就会出现耳聋、胁肋疼痛、口苦、呕吐、舌苔白、脉象弦等症。如果传入阳明腑证，属于病邪入里，会出现舌苔黄、口渴、心烦、舌干、不怕冷反而怕热、手足躁动不安、掀开衣被、胡言乱语、神志不清、脉象洪数且内部实邪积聚的证候。适宜使用泻下剂。如果泻下太迟，病邪就会传入阴经，出现舌头黑大等症状。凡是伤寒的热病，完全不间断，直到病邪传入里部，使用泻下法之后才停止。医经说：夏天感受暑邪，秋天必定发生疟疾。夏天中暑而不出汗，秋天形成风疟。由此可知，疟疾的发生，多因于暑邪。所以发生瘴气的地方，四季常像夏天一样。这种病没有传经的过程。如果是冷瘴，则有怕冷发热、头痛、脚弱、腰重、口中不和、呕吐或不呕吐、脉象弦而带数，一呼一吸之间，脉搏跳动六次，或者七次八次。或者先冷后热，或者先热后冷。当其寒冷时，脉象沉迟而伏；等到发热时，脉象六至七至，且弦洪、口渴想喝水，喝水后容易呕吐，掀开衣被，等到出汗后，热势就会消退。或者无汗但热势久了也会消退，或者隔天发作一次，或者一天发作一次，这属于轻症。如果是热瘴，则不怕冷只发热，壮热、头痛、身体疲倦、腰重脚弱、烦躁、胸膈不利、呕吐或不呕吐、腹泻或不腹泻、小便赤涩、口渴、脉象洪弦七至八次，热势也不间断。一到两天舌头变黑，眼睛红、面色赤红，渴望喝冷水，给水也能喝，胡言乱语、神志不清，或者大便闭结，到傍晚时分尤其严重。这与伤寒的里实证无异。仔细检查发现，身体内部的热有凉的地方，用手触摸，额头极热，面部微热，鼻尖凉，心胸及腹部极热，背部微热，腰部以下不太热，严重的常年寒冷，或者四肢厥冷且胡言乱语，用手触摸心胸部位，患者蜷缩而卧又狂躁起身，那么脚重无力是怎么回事呢？瘴病是上热下寒，所以腰部以下不热而沉重。上半身的症状，虽然是阳证而阴证潜伏其中，症状隐含在其中。鼻尖为年寿宫，年寿属脾，脾寒所以鼻尖凉。这个病是外热内寒，热症虽然表现在外面，而内寒的症候，通过鼻尖凉来验证。蜷缩而卧、双手交叉护胸，胃和胸部的隐痛就显现出来了。有人说这是伤寒的阴证，似阳非阳。如果是阴证似阳，口渴想喝冷水，给冷水则不喝。瘴病给冷水则能喝。如果使用药物得当，热势就会消退。或者隔日发热，退热时脉象微弱，不再像之前那样洪大、弦急、数快了。大体来说，瘴病与伤寒大不相同。伤寒因于寒邪，瘴病因于暑邪。伤寒有传经过程，有变证，有传染性。而瘴病不传经，无变证，不传染。如果医生错误地把恶寒发热当作表证，使用伤寒的发汗药；把胡言乱语、大便秘结、舌苔黑当作里证，使用伤寒的泻下药，那么不久就会病情突变而导致死亡。
In the southern regions, the changes of cold and heat are irregular. During spring and summer, excessive rain leads to an abundance of cold; morning and evening fog creates a humid atmosphere with dampness steaming from the ground, causing Yin-damp Qi to be often prevalent. In autumn and winter, prolonged sunshine results in excessive heat, where grasses and trees do not wither but bloom, causing Yang-warm Qi to frequently dissipate. Days are hot, nights are cold; sunny days are hot, rainy days are cold. Humans living in such environments, due to the prevalence of cold-damp Qi, experience heaviness and dampness in the lower body and generate more phlegm. The production of phlegm is attributed to the heat of autumn and winter; excess heat tends to obstruct upwards. The skin sweats easily, leading to loose *Couli* (pores and interstices), with Yang floating outward and Yin closing inward, Yang drifting and Yin blocking. At this time, if dietary habits are irregular, daily routines are untimely, or raw/cold foods and roasted/dry foods are consumed, phlegm and food stagnation accumulate together in the stomach, triggering alternating chills and fever. One might not avoid the heat, running under the sun, or seek shade while sitting/lying in the wind, closing sweat pores and preventing perspiration, which also induces this disease. Or, due to morning mist and cold, one drinks alcohol to ward it off; shortly after sunrise, heat arises, causing wine and phlegm to stagnate above the diaphragm, inducing this disease. Or wearing too little in the morning cold, or too thin quilts at night, causing cold and phlegm to combine, resulting in chills and fever. Or wearing too much in the morning cold and not removing it by noon, causing summer-heat and phlegm to combine, also resulting in chills and fever. Essentially, the root of this disease lies in the heavenly heat causing constant leakage of primal Yang Qi; human Yang Qi fails to descend, and internal phlegm is abundant. Without proper care, contracting pathogenic factors, symptoms of upper heat and lower cold naturally arise. This is what is meant by "no phlegm, no malaria." Those who practice health preservation can avoid this even toxic miasma by avoiding sexual activity, reducing labor, abstaining from raw/cold and roasted foods, avoiding early drunkenness, not overeating at dinner, not walking in summer heat, and not sitting/lying in drafts. Adjusting clothing according to temperature changes throughout the day allows one to largely escape the disease.
The symptoms of external cold invasion and zhang-malaria both present with chills and fever. Physicians often mistake zhang-malaria for shang-han (cold damage) and indiscriminately use sweating, vomiting, or purging methods. Countless patients have died wrongly due to this failure to distinguish between cold and heat patterns. Now, let us differentiate them clearly. The Classics state: "Winter injury by cold leads to epidemic fevers in spring." If illness occurs immediately in winter, it is called Shanghan. If delayed until spring, it becomes a Wenbing (warm disease); if delayed until summer, it becomes a Rebing (heat disease). Such diseases usually begin in the Taiyang Meridian. Thus, there is fever, aversion to cold, headache, stiff spine, absence of sweating, a normal mouth without bitterness, normal appetite, and a floating-tight pulse—this is Shanghan. Or, with aversion to wind, spontaneous sweating, and a floating-slow pulse—this is Shangfeng (wind injury). If the heat persists and transmits to the Yangming Meridian, symptoms include eye pain, dry nose, insomnia, and a long pulse. If transmitting to the Shaoyang Meridian, symptoms include deafness, hypochondriac pain, bitter taste, vomiting, white tongue coating, and a wiry pulse. If entering the Yangming Fu-organs (interior), symptoms include yellow tongue coating, thirst, mental restlessness, dry tongue, aversion to heat rather than cold, restless tossing, removing clothes/bedding, delirious speech, and a flooding-rapid pulse indicating interior excess. Purging agents are indicated. Delayed purging allows entry into the Yin meridians, presenting with a black, enlarged tongue. Shanghan heat is continuous until transmitted to the interior and purged. The Classics state: "Summer injury by summer-heat leads to malaria in autumn." Summer-heat without sweating leads to wind-malaria in autumn. Thus, malaria often originates from summer-heat. In miasma-prone areas, seasons resemble summer year-round. This disease does not transmit through meridians. Cold-zhang presents with chills and fever, headache, weak legs, heavy waist, oral discomfort, vomiting or not, wiry-numerous pulse (6-8 beats per respiration), alternating chills/fever. During chills, the pulse is deep-slow-hidden; during fever, it is 6-7 beats, wiry-flooding, with thirst for water, vomiting after drinking, restlessness, resolving upon sweating. Or no sweat but heat subsides eventually, occurring every other day or daily (mild cases). Hot-zhang presents with no chills, only high fever, headache, fatigue, heavy waist/legs, irritability, chest oppression, vomiting or not, diarrhea or not, dark-scanty urine, thirst, flooding-wiry pulse (7-8 beats), continuous heat. Within 1-2 days, the tongue turns black, eyes red, face red, craving cold water (drinks it), delirium, constipation worsening at dusk. This resembles Shanghan interior excess. Careful palpation reveals uneven heat: forehead very hot, face slightly hot, nasal tip cool, chest/abdomen very hot, back slightly hot, lower body less hot. Severe cases feel constantly cold or have cold limbs with delirium. Palpating the chest shows curling up then rising wildly. Why are legs heavy? Zhang disease is upper heat/lower cold, hence lower body is cool and heavy. Upper body symptoms appear Yang but hide Yin. The nasal tip is the Nienshou Palace, belonging to the Spleen; spleen cold makes the nasal tip cool. This is exterior heat/internal cold; exterior heat masks internal cold, verified by cool nasal tip. Curling up and crossing hands indicates hidden stomach/chest issues. Some call this Yin-pattern resembling Yang, but it is not. Yin-resembling-Yang craves cold water but refuses it when given. Zhang patients drink cold water. Proper medication resolves heat. If intermittent, pulse becomes weak upon resolution, no longer flooding/wiry/rapid. Generally, Zhang differs greatly from Shanghan. Shanghan stems from cold, has meridian transmission, transformations, and contagion. Zhang stems from summer-heat, has no transmission, no transformation, and no contagion. Mistaking chills/fever for exterior syndrome and using Shanghan sweating herbs, or mistaking delirium/constipation/black tongue for interior syndrome and using purging herbs, will lead to rapid deterioration and death.