唐容川曰∶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，医者多隅反。
经云∶春善病鼽衄。
唐容川曰∶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，谓多此种也。
涂蔚生曰∶春季界于冬寒夏热二者之间，人当此际，最易疏忽，以其时令略为和暖，可以少受寒、亦可以少
受热。故鼽衄二症，此时为多，容川衄血之解尤为有见。
经云∶仲夏善病胸胁。
唐容川曰∶胸是两乳中间属心，肋是两乳旁边属三焦。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。
经云∶长夏善病洞泄寒中。
唐容川曰∶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。
涂蔚生曰∶此节是由热而病寒，上节是由热而病火，两节恰是一个对字。容川此解，是未免过泥时令，而不
能揆诸人情，衡乎事实者也。盖长夏热之最盛者也，惟热最盛，故人亦恶热最甚。于水果生冷之物，每多任意吃
啖，以求御热避燥，迨其身体清爽之意。孰知内之阳火有限，而外之物欲无穷，旦旦而伐之，其不为阳火衰败也几希。
迨至胃寒既成，则水谷当然不能消化，发生洞泻寒中等症。夏日偏多痧症霍乱之症，亦即此理。若谓脾主湿而恶湿，
湿甚则洞泻，阳极于外，无以温养中土，故发寒中之病，是人之胃阳，因外之阳热过甚，变而寒矣。然吾人之一呼
一吸，纯与外阳相通，岂有外阳既热，而吾人吸入之气，尚为阴寒者哉。吾故曰∶夏月洞泻寒中，全由过食生冷之
故。至谓冬月井水温，夏月井水冷，此则由于井水与空气之比较使然，实则井水常一也。不过空气有寒热，而吾人
之手指，始觉有冷暖耳。
经云∶秋善病风疟。
唐容川曰∶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，腠理自和。设风气鼓动，则为皮毛不得敛而发寒热。风火相煽，则腠理不得和，
而战栗溺赤。知此理者，可得治疟之法也。
涂蔚生曰∶风是伤人瘦肉一层，疟是居人腠理一层，腠理尚在瘦肉外，何以因风致疟。盖因风未能解散清楚，
而逆居于腠理之间也。昔黄帝问于岐伯曰∶夫风之与疟也，相似同类，而风独常在，疟得有时而休者，何也？岐
伯曰∶风气留其处故常在，疟气随经络沉以内薄，故卫气应乃作。是风自风而疟自疟，不可因风以及疟也。然岐伯
又曰∶先伤于寒，而后伤于风，故先寒而后热也。病以时作，名曰寒疟。先伤于风，而后伤于寒，故先热而后寒也。
亦以时作，名曰温疟。其但热而不寒者，阴气先绝，阳气独发，则少气烦冤，手足热而欲呕，名曰瘅疟。是疟有因风
者，有不因风者，未可以类推也。如欲尽治疟之能事，须参观《内经》之疟症论，与后集之疟疾症治，方可胸有成竹，
不致误事。
经云∶冬善病痹厥。
唐容川曰∶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。
唐容川曰∶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。
唐容川说：四季各有其主气和客气，五方地域存在强弱差异。这里所列举的，不过是为了阐明脏腑之气应与天时同步运行的道理罢了，医生们大多能由此举一反三。
唐容川说：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，就会导致鼻塞不通，治疗应当疏散寒邪。衄属于血分病变，春季肝木生心火，火热扰动血液向上冲逆，侵犯清窍，鼻为肺之窍，肝木之火反侮肺金，所以发生鼻衄，治疗应当清降火热。所谓“善病”，意思是容易患这类疾病。
涂蔚生说：春季处于冬季寒冷和夏季炎热之间，人们在这个时候最容易疏忽大意，因为时令稍微和暖，既可以少受寒，也可以少受热。所以鼻塞流涕和鼻出血这两种症状，此时最为多见，唐容川对鼻衄的解释尤其有见地。
《内经》说：仲夏容易发生胸胁部不适的病证。
唐容川说：胸部位于两乳中间，归属于心；胁部位于两乳旁边，归属于三焦。心是君火，三焦是相火，都与夏季的气候相应。所以仲夏容易发生胸胁部病证，是因为火气有余，多导致气逆胀满。
《内经》说：长夏容易发生洞泄（水样腹泻）和中寒的病证。
唐容川说：长夏六月，湿土之气当令。脾脏主管湿气但厌恶湿气，湿气过重就会引发洞泻。阳气极盛于体表，无法温养中焦脾胃，所以发生中寒的病证。观察冬天井水温暖、夏天井水冰冷，就可以知道夏季中焦脾胃多寒了。
涂蔚生说：这一节讲的是由热转寒致病，上一节讲的是由热转火致病，这两节恰好形成对照。唐容川的这种解释，未免过于拘泥于时令节气，而不能揣度人情、衡量事实。长夏是一年中热最盛的时候，正因为热最盛，所以人也最厌恶热。对于水果生冷之物，人们往往任意食用，以求抵御炎热、避免燥热，达到身体清爽的目的。殊不知体内的阳火是有限的，而外在的欲望是无穷的，天天这样伐损，那么不导致阳火衰败的情况就太少了。等到胃寒形成之后，水谷自然不能消化，从而发生洞泄、中寒等症状。夏天偏多的痧症、霍乱等病证，也是这个道理。如果说脾主湿而恶湿，湿气重则洞泻，阳气极盛于外，无法温养中土，所以发生中寒病证，这是认为人的胃阳因为外界阳热过甚，反而变成了寒。然而我们的一呼一吸，完全与外界的阳气相通，难道外界阳气已经炎热，而我们吸入的气息还是阴寒的吗？所以我说是因为夏天过度食用生冷食物才导致洞泄和中寒。至于说冬天井水温暖、夏天井水冰冷，这是由于井水与空气比较的结果，实际上井水温度始终如一。只不过空气有寒热之分，我们的手指接触时，才感觉到冷暖而已。
唐容川说：风邪归属于肝，疟疾归属于少阳胆经。因风致疟，本质上是木火为病，多发于秋季，是因为木火反侮肺金。秋季正值肺金主气之时，金气清肃，皮毛自然收敛，腠理自然调和。如果风气鼓动，导致皮毛不能收敛而发寒热。风火相互煽动，导致腠理不能调和，出现战栗、小便赤黄。懂得这个原理，就可以掌握治疗疟疾的方法。
涂蔚生说：风邪伤害人体瘦肉一层，疟邪潜伏在人体腠理一层，腠理还在瘦肉之外，怎么会因风致疟呢？这是因为风邪未能彻底解散，反而逆居于腠理之间。昔日黄帝问岐伯说：风病和疟病，相似且同类，为什么风病常常持续存在，而疟病却有时休止呢？岐伯回答说：风邪停留在发病部位，所以常存；疟邪随着经络深入体内，卫气运行到那里才发作。这说明风就是风，疟就是疟，不能简单地由风推导出疟。然而岐伯又说：先伤于寒，后伤于风，所以先冷后热，按时发作，名叫寒疟。先伤于风，后伤于寒，所以先热后冷，也按时发作，名叫温疟。只有热而不冷的，是阴气先绝，阳气独发，导致少气烦冤、手足发热想呕吐，名叫瘅（dān）疟。可见疟疾有的因风引起，有的不因风引起，不可以类推。如果想要穷尽治疗疟疾的能力，必须参考《内经》中的疟症论，以及后集关于疟疾症治的内容，才能胸有成竹，不至于误事。
唐容川说：痹是指骨节疼痛，厥是指四肢逆冷。肾中的阳气能通达于骨节，充盈于四肢末端，就不会有此病。冬季寒水之气旺盛，往往肾阳不足，所以多发生此类病证。
唐容川说：四季的疾病，不胜枚举，但上述几种最为多见。并且懂得了这些道理，那么一切非时发生的疾病，其机理都可以认识了。
Tang Rongchuan stated: Each of the four seasons has its dominant qi (vital energy) and guest qi, with variations in strength across the five directions. What is cited here merely clarifies the principle that the qi of the zang-fu organs should run in parallel with the timing of heaven and earth; physicians are often able to infer other cases from this single example.
The Classics state: In spring, diseases such as rhinorrhea (nasal congestion with discharge) and epistaxis (nosebleed) are prevalent.
Tang Rongchuan explained: Rhinorrhea refers to nasal congestion with discharge, while epistaxis refers to nosebleeds. Rhinorrhea belongs to the Qi level. In spring, Yang qi exerts itself outward; if obstructed by Yin cold, it leads to nasal blockage. Treatment should focus on dispersing cold. Epistaxis belongs to the Blood level. In spring, Liver Wood generates Heart Fire; this fire agitates Blood and rushes upward, invading the clear orifices. Since the nose is the opening of the Lung, Liver-Wood Fire insulting Lung-Metal causes epistaxis. Treatment should focus on clearing and descending fire. "Prone to disease" means frequently suffering from these conditions.
Tu Weisheng commented: Spring lies between winter cold and summer heat. People are most likely to be negligent at this time because the weather is slightly warm, allowing for both slight exposure to cold and slight exposure to heat. Therefore, rhinorrhea and epistaxis are common during this period. Tang Rongchuan’s explanation of epistaxis is particularly insightful.
The Classics state: In mid-summer, diseases of the chest and hypochondrium are prevalent.
Tang Rongchuan explained: 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 is Ministerial Fire (Jun Huo), and the Sanjiao is Assistant Fire (Xiang Huo); both correspond to the summer climate. Thus, in mid-summer, chest and hypochondriac diseases occur because excess Fire often leads to rebellious Qi and fullness.
The Classics state: In late summer, severe diarrhea (dong xie) and middle-jiao cold are prevalent.
Tang Rongchuan explained: In the sixth month of late summer, Damp-Earth qi dominates. The Spleen governs dampness but dislikes dampness; excessive dampness triggers severe diarrhea. When Yang qi reaches its peak on the exterior, it fails to warm and nourish the Middle Earth (Spleen/Stomach), leading to middle-jiao cold. Observing that well water is warm in winter and cold in summer reveals that the middle jiao tends to be cold in summer.
Tu Weisheng commented: This section describes illness arising from heat transforming into cold, whereas the previous section described heat transforming into fire; the two sections form a contrast. Tang Rongchuan’s interpretation is somewhat too rigid regarding seasonal timing, failing to account for human nature and factual reality. Late summer is the hottest time of the year; consequently, people dislike heat most intensely. They often consume fruits and raw/cold foods arbitrarily to resist heat and dryness, seeking physical refreshment. However, internal Yang fire is limited, while external desires are infinite. Daily depletion makes it unlikely that Yang fire would not decline. Once stomach cold is established, food and water cannot be digested, resulting in severe diarrhea and middle-jiao cold. The prevalence of sha syndrome and cholera-like symptoms in summer follows this same logic. If one argues that Spleen governs dampness and dislikes it, so excess dampness causes diarrhea, and extreme exterior Yang fails to warm the Middle Earth causing cold, this implies that human Stomach Yang transforms into cold due to excessive external heat. Yet, our breathing connects purely with external Yang. How could the air we inhale be Yin-cold when external Yang is hot? Therefore, I assert that summer severe diarrhea and middle-jiao cold are entirely due to overconsumption of raw and cold foods. Regarding the observation that well water is warm in winter and cold in summer, this results from the comparison between well water and air; in reality, well water temperature remains constant. It is only because air has temperature variations that our fingers perceive cold or warmth upon contact.
The Classics state: In autumn, wind-malaria (malaria induced by wind pathogen) is prevalent.
Tang Rongchuan explained: Wind corresponds to the Liver, and malaria corresponds to the Shaoyang Gallbladder. Malaria caused by wind is essentially a Wood-Fire pathology. Its prevalence in autumn is due to Wood-Fire insulting Metal. Autumn is when Lung-Metal qi dominates; Metal qi is clear and肃 (solemn/cleansing), causing skin pores to close naturally and interstices (cou li) to harmonize. If wind agitates, preventing pore closure, chills and fever occur. If wind and fire fan each other, interstices fail to harmonize, leading to shivering and dark urine. Understanding this principle allows one to master the treatment of malaria.
Tu Weisheng commented: Wind pathogen affects the flesh layer, while malaria pathogen resides in the interstitial layer. Since interstices are outside the flesh, how can wind cause malaria? It is because the wind pathogen was not fully resolved and instead lodged reversely in the interstices. Formerly, the Yellow Emperor asked Qibo: Wind and malaria are similar and of the same category, yet wind persists constantly while malaria has periods of remission. Why? Qibo replied: Wind qi stays in its location, hence it persists; malaria qi sinks along the meridians and enters inward, manifesting only when Wei Qi (Defensive Qi) arrives. This shows wind is wind and malaria is malaria; one cannot simply deduce malaria from wind. However, Qibo also stated: Injury by cold first, then wind, results in chills followed by heat, occurring at specific times, named Cold Malaria. Injury by wind first, then cold, results in heat followed by chills, also occurring at specific times, named Warm Malaria. Cases with only heat and no chills indicate prior exhaustion of Yin qi, with solitary Yang flare-up, causing shortness of breath, oppression, heat in hands and feet, and nausea, named Dan Malaria. Thus, some malaria cases are wind-induced, others are not; they cannot be generalized. To fully master malaria treatment, one must consult the Malaria discussions in the *Neijing* and the subsequent collection on malaria syndromes and treatments, ensuring thorough understanding to avoid errors.
The Classics state: In winter, Bi obstruction (joint pain) and Jue reversal (cold limbs) are prevalent.
Tang Rongchuan explained: Bi refers to joint pain; Jue refers to cold extremities. If Kidney Yang qi can reach the joints and fill the four extremities, these diseases do not occur. In winter, Cold-Water qi is strong; often, Kidney Yang is insufficient, leading to frequent occurrence of these diseases.
Tang Rongchuan concluded: Diseases of the four seasons are numerous, but these are the most common. By understanding these principles, the mechanisms of all out-of-season diseases can be recognized.