伤寒，是寒气客于皮肤，搏于血气，腠理闭密，气不得宣泄，蕴积毒瓦斯，故头痛、体疼
而壮热。其鼻衄，是热搏于气，而乘于血也。肺候身之皮毛，其气开窍于鼻。蕴寒先客皮肤
，搏于气而成热，热乘于血，血得热而妄行，发从鼻出者，名鼻衄也。
凡候热病而应衄者，其人壮热，频发汗，汗不出，或未及发汗，而鼻燥喘息，鼻气鸣即
衄。凡衄，小儿止一升数合，则热因之得歇；若一升二升者，死。
伤寒，是寒气客于皮肤，搏于血气，使腠理闭密，气不宣泄，蕴积毒瓦斯，头痛、体疼而
壮热也。其热歇后而利者，是热从表入里故也。表热虽得解，而里热犹停肠胃，与水谷相并
，肠胃虚则泄利。其状，利色黄。若壮热不止，则变为血利。若重遇冷，则冷热相加，则变
赤白泻利也。
时气病者，是四时之间，忽有非节之气，如春时应暖而反寒，夏时应热而反冷，秋时应
凉而反热，冬时应寒而反温。其气伤人，为病亦头痛、壮热，大体与伤寒相似，无问长幼，
其病形证略同。言此时通行此气，故名时气。世亦呼为天行。
四时之间，忽有非节之气伤人，谓之天行。大体似伤寒，亦头痛壮热。其热入于脾胃，
停滞则发黄也。脾与胃合，俱象土，其色黄，而候于肌肉。热气蕴积，其色蒸发于外，故发
伤寒，是寒气侵袭皮肤，与血气相搏结，导致腠理（皮肤纹理及汗孔）闭塞致密，气机无法宣泄，蕴积毒瓦斯，因此出现头痛、身体疼痛以及高热。其中的鼻衄（鼻出血），是因为热邪搏结于气分，进而侵入血分所致。肺主司身体的皮毛，其气机开窍于鼻。寒邪先侵袭皮肤，与气相搏而化热，热邪乘袭血分，血液受热则妄行，从鼻腔流出，这种病症称为鼻衄。
凡是诊察热病且应当出现鼻衄的患者，其人表现为高热，频繁出汗但汗出不畅，或者尚未发汗，就出现鼻干、喘息、鼻中气息鸣响随即发生鼻衄。凡是大出血，小儿失血量在一升到数合之间，热邪就会因此得以平息；若失血量达到一升二升，则预后不良，会导致死亡。
伤寒，是寒气侵袭皮肤，与血气相搏结，使腠理闭塞致密，气机不得宣泄，蕴积毒瓦斯，从而引起头痛、身体疼痛和高热。在热势消退后出现腹泻的，是因为热邪由表入里所致。虽然表层的热邪已解，但里热仍然停滞在肠胃，与水谷相互搏结，肠胃虚弱则导致泄泻痢疾。其症状表现为大便颜色发黄。如果高热不止，则会转变为便血（血利）。如果再重感寒冷，则冷热之邪相加，会变为赤白相间的痢疾（赤白泻利）。
时气病，是指在四季之中，突然出现了不合节令的气候，例如春天应该温暖却反而寒冷，夏天应该炎热却反而凉爽，秋天应该清凉却反而炎热，冬天应该寒冷却反而温暖。这种异常气候伤害人体致病，症状也是头痛、高热，大体上与伤寒相似，无论老少，其病情和证候大致相同。因为此时普遍流行这种气候之气，所以称为时气。世人也将它称为天行（时行疫病）。
四季之中，突然出现的非节令之气伤害人体，称为天行。大体上类似伤寒，也出现头痛和高热。如果热邪进入脾胃，停滞积聚就会导致发黄。脾与胃相合，都象征土，其色为黄，并反映在肌肉状况上。热气蕴积，其黄色蒸发显现于体表，因此发生黄疸。
Shanghan (Cold Damage) is caused by cold qi invading the skin, clashing with blood and qi, causing the couli (skin pores and interstices) to become closed and dense. As a result, qi cannot be diffused, leading to the accumulation of toxic vapors, which causes headache, body pain, and high fever. The occurrence of biyu (epistaxis/nosebleed) in this context is due to heat clashing with qi and then invading the blood. The Lung governs the skin and hair of the body, and its orifice opens at the nose. Cold qi first invades the skin, clashes with qi to generate heat, and then the heat attacks the blood. When blood is heated, it flows recklessly and exits from the nose; this condition is named biyu (epistaxis).
In general, when observing febrile diseases that should manifest as epistaxis, the patient presents with high fever, frequent sweating but with incomplete sweat discharge, or before sweating therapy has been applied, symptoms such as dry nose, panting, and nasal resonance occur, followed immediately by epistaxis. In cases of significant bleeding, if a child loses between one sheng and several he (ancient volume units), the heat will subside due to this loss; however, if the loss reaches one to two sheng, the prognosis is fatal.
Shanghan (Cold Damage) involves cold qi invading the skin, clashing with blood and qi, making the couli (skin pores and interstices) closed and dense, preventing qi diffusion, and accumulating toxic vapors, resulting in headache, body pain, and high fever. If diarrhea occurs after the heat subsides, it is because the heat has moved from the exterior to the interior. Although the exterior heat has resolved, interior heat remains stagnant in the intestines and stomach, combining with food and fluids. Due to the deficiency of the intestines and stomach, this leads to diarrhea and dysentery. The stool appears yellow. If high fever persists without stopping, it may transform into bloody stools (blood dysentery). If exposed to severe cold subsequently, the cold and heat pathogens combine, transforming into dysentery with both red and white discharge (red and white dysentery).
Shiqi Bing (Seasonal Qi Disease) refers to abnormal, non-seasonal climatic conditions occurring suddenly during the four seasons, such as cold weather in spring when warmth is expected, coolness in summer when heat is expected, heat in autumn when coolness is expected, and warmth in winter when cold is expected. This pathogenic qi damages the human body, causing symptoms like headache and high fever. Generally, it resembles Shanghan (Cold Damage); regardless of age, the clinical manifestations are roughly identical. Because this pathogenic qi circulates widely during this specific time, it is called Shiqi (Seasonal Qi). It is also commonly referred to as Tianxing (Epidemic/Contagious Disease).
When abnormal, non-seasonal qi in the four seasons damages the human body, it is called Tianxing (Epidemic/Contiguous Disease). It generally resembles Shanghan (Cold Damage), presenting with headache and high fever. If the heat enters the Spleen and Stomach and stagnates, it leads to jaundice (yellowing). The Spleen and Stomach are paired and correspond to the element Earth, whose color is yellow, and they reflect on the muscles. When heat qi accumulates, its yellow color evaporates and manifests externally, thus causing jaundice.