四时各有主气。客气五方强弱之异兹所举者。不过明脏腑气应与天时并行之义耳。医者当知隅反。
春善病鼽衄。
鼽是鼻塞流涕。衄是流鼻血。鼽属气分。春阳发泄。为阴所闭则鼻塞不通。治宜疏散其寒。衄属血分。春木生火。
动血上冲。干犯清道。鼻为肺窍。木火侮肺。故发衄。治宜清降其火。善病者。谓多此种病也。
仲夏善病胸胁。
胸是两乳中间属心。胁是两乳旁边。属三焦。心是君火。三焦是相火。皆与夏气相应。故仲夏善病胸胁。以火有余。
多发逆满也。
长夏善病洞泻寒中。
长夏未。月湿土主气。脾主湿而恶湿。湿甚则发洞泻阳极于外。无以温养中土。故发寒中之病。观冬月井水温。夏
月井水冷。则知夏月。中宫多寒矣。
秋善病风疟。
风属肝疟属少阳。因风致疟。本系木火为病。而多发于秋令者。木火侮金也。盖秋当肺金主气之时。金气清肃。则
皮毛自敛。膜腠自和设风气鼓动。则为皮毛不得敛。而发寒热。风火相煽。则膜腠不得和。而战栗。溺赤。知此理者。
可得治疟之法矣。
冬善病痹厥。
痹是骨节疼痛。厥是四肢逆冷。肾中阳气。能达于骨节。充于四末。则无此病。冬令寒水气盛。往往肾阳不足。故
多此病。
四时之病不一而足。则此种为多。且知其理。而一切非时之病。理皆可识。
四季各有其主司的气候之气。客气在五方强弱方面的差异，此处所列举的，不过是为了阐明脏腑之气应与天时并行运行的道理罢了。医者应当能够由此类推。
春季容易发生鼻塞流涕和鼻出血的病证。
鼽（qiú）是指鼻塞流涕。衄（nǜ）是指流鼻血。鼽属于气分病变。春季阳气发泄，若被阴寒所闭阻，则导致鼻塞不通。治疗宜疏散其寒邪。衄属于血分病变。春季木气生发化为火气，扰动血液向上冲逆，侵犯清窍。鼻为肺之窍，肝木之火反侮肺金，因此发生鼻衄。治疗宜清降其火气。所谓“善病”，是指容易患这类疾病的意思。
仲夏（夏季的第二个月）容易发生胸胁部的病证。
胸位于两乳之间，归属于心。胁位于两乳旁边，归属于三焦。心为君火，三焦为相火，都与夏季的气候相应。所以仲夏容易发生胸胁部的病证，这是因为火气有余，容易导致气机逆乱而胀满。
长夏容易发生洞泄和寒中病证。
长夏时节，湿土之气主令。脾脏主运化湿气但厌恶湿气，湿气过重则引发洞泄（急骤的水样腹泻）。阳极于外，体内无以温养中焦脾胃，因此发生寒中病证。观察冬天井水温暖、夏天井水寒冷，就可以知道夏季中焦（脾胃）多寒凉。
秋季容易发生风疟病证。
风邪归属于肝，疟疾归属于少阳胆经。因风邪诱发疟疾，本属木火为病，却多发于秋季，这是因为木火反侮肺金。大概秋季是肺金主气的时节，金气清肃，则皮毛自然收敛，腠理自然调和。如果风气鼓动，则皮毛不能收敛，从而引发寒热往来；风火相互煽动，则腠理不能调和，从而出现战栗、小便赤黄。懂得这个道理，就可以掌握治疗疟疾的方法了。
冬季容易发生痹证和厥证。
痹证是指骨节疼痛。厥证是指四肢逆冷。肾中的阳气若能通达于骨节，充盈于四肢末端，就不会发生这些病证。冬季寒水之气旺盛，往往导致肾阳不足，所以容易发生这些病证。
四季的疾病不止上述几种，但以上这些较为多见。况且通晓了其中的道理，那么一切非时发生的疾病，其机理也都可以认识了。
Each of the four seasons has its dominant climate. The variations in the strength and weakness of the Guest Qi (Ke Qi, 客气) among the five directions are not fully detailed here; what is presented merely clarifies the principle that the Qi of the Zang-Fu organs should run in parallel with the timing of Heaven and Earth. Physicians should be able to infer other cases from this example.
In spring, diseases such as nasal obstruction with discharge (Qiu, 鼽) and epistaxis (Nu, 衄) are prevalent.
Qiu refers to nasal obstruction with discharge. Nu refers to nosebleed. Qiu belongs to the Qi level. In spring, Yang Qi tends to disperse outward; if it is obstructed by Yin (Cold), nasal obstruction occurs. Treatment should aim to dissipate the Cold. Nu belongs to the Blood level. In spring, Wood generates Fire, which agitates Blood and causes it to rush upward, invading the clear orifices. The nose is the opening of the Lung. Wood-Fire insults Metal (Lung), leading to epistaxis. Treatment should aim to clear and descend the Fire. "Shan bing" (prone to disease) means being susceptible to these types of illnesses.
In mid-summer, diseases affecting the chest and hypochondrium are prevalent.
The chest, located between the two breasts, corresponds to the Heart. The hypochondrium, located beside the two breasts, corresponds to the Sanjiao (Triple Burner). The Heart governs Ministerial Fire (Jun Huo, 君火), and the Sanjiao governs Official Fire (Xiang Huo, 相火); both correspond to the summer climate. Therefore, in mid-summer, diseases of the chest and hypochondrium are common, primarily because excess Fire often leads to rebellious Qi and fullness.
In late summer, severe diarrhea and cold invasion of the middle jiao are prevalent.
During late summer, Dampness and Earth Qi dominate. The Spleen governs Dampness but dislikes Dampness; excessive Dampness triggers severe diarrhea (Dong Xie, 洞泻). When Yang reaches its extreme outwardly, there is insufficient warmth to nourish the Middle Earth (Spleen/Stomach), resulting in Cold invasion of the middle. Observing that well water is warm in winter and cold in summer reveals that the Middle Jiao is often cold during summer.
In autumn, wind-induced malaria is prevalent.
Wind is associated with the Liver, and malaria is associated with the Shaoyang Gallbladder. Malaria induced by wind originates from Wood-Fire pathology but frequently occurs in autumn due to Wood-Fire insulting Metal (Lung). Autumn is when Lung Metal dominates; Metal's clear and肃 (descending/clearing) nature allows the skin and hair pores to close naturally and the interstices (Mo Cou, 膜腠) to harmonize. If Wind agitates, the skin cannot close, causing alternating chills and fever. If Wind and Fire fan each other, the interstices fail to harmonize, causing shivering and dark urine. Understanding this principle enables one to master the treatment of malaria.
In winter, Bi syndrome (obstruction) and Jue syndrome (reversal/cold limbs) are prevalent.
Bi syndrome refers to pain in the bone joints. Jue syndrome refers to cold extremities. If the Kidney's Yang Qi can reach the bone joints and fill the four extremities, these diseases do not occur. In winter, Cold Water Qi is strong, often leading to insufficiency of Kidney Yang, hence the prevalence of these diseases.
The diseases of the four seasons are numerous, but those mentioned above are common. Furthermore, once the underlying principles are understood, the pathogenesis of any disease occurring out of season can also be recognized.