既讲春夏秋冬之异。须知昼夜阴晴之殊。盖人在气交之中。与气候之相应也。犹影之随身。犹水之鉴形。
夫是故昼为阳。卫气日行于阳。夜为阴。卫气夜行于阴。天温日阳。则人血淖溢而卫气浮。天寒日阴。则人
血凝泣而卫气沉。血气营卫之相应如此。则色之相应可征矣。何者。脉以应月。色以应日。昼则气行于阳。
色之见也。当光辉而外映。夜则气行于阴。色之见也。当明润而内含。晴则气热。热则气淖泽。淖泽则黄赤。
阴则气寒。寒则血凝泣。凝泣则青黑。此皆其应也。色之应乎昼夜阴晴者。常也。不应乎昼夜阴晴者。病也。
夫百病多以旦慧、昼安、夕加、夜甚。色当因病之旦慧、昼安、夕加、夜甚也。其或暮轻朝重。夜减昼加。则不在
乎卫气。而独主乎脏气矣。是必以脏气之所不胜时者甚。以其所胜时者起。夫所不胜者。克我者也。所胜
者。我克者也。盖以一日分为四时。以四时分应五脏。肝日甲乙。其时寅卯。心日丙丁。其时巳午。肺日庚辛。
其时申酉。肾日壬癸。其时亥子。脾日戊己。其时辰戌丑未。以五脏之日时。合五脏之病色。其生克之理。间
甚之候。死生之期。胥于是乎推。亦于是乎断矣。然而一日之内。一时之间。寒暄不齐。雨 靡定。则又各有
所胜。各有所不胜矣。若夫宫室有冷暖之殊。衣服有寒温之异。病或因之而重轻。色或因之而损益。虽不
当以昼夜论。亦皆可作阴晴观。触目关心。存乎人矣。
Having discussed the differences among Spring, Summer, Autumn, and Winter, one must also understand the distinctions of Day, Night, Clear weather, and Overcast weather. This is because humans exist within the intersection of Heaven and Earth Qi (vital energy), responding to climatic changes. It is like a shadow following the body, or like water reflecting a form.
Therefore, Day belongs to Yang, during which Wei Qi (Defensive Qi) circulates in the Yang aspects (exterior/body surface) by day; Night belongs to Yin, during which Wei Qi circulates in the Yin aspects (interior/organs) by night. When the weather is warm and sunny, human blood flows smoothly and abundantly, and Wei Qi floats outward; when the weather is cold and overcast, human blood becomes sluggish and congealed, and Wei Qi sinks inward. Such is the correspondence between Blood-Qi and Ying-Wei (Nutritive and Defensive Qi). Thus, the corresponding changes in facial complexion can be verified. Why? Because Pulse corresponds to the waxing and waning of the Moon, while Complexion corresponds to the Sun’s day and night cycle. During the day, Qi moves in the Yang aspects; thus, the manifestation of complexion should be radiant and externally visible. At night, Qi moves in the Yin aspects; thus, the manifestation of complexion should be bright, moist, and internally contained. On clear days, the Qi is warm; warmth makes Qi smooth and lubricated; smoothness and lubrication result in a yellowish-red complexion. On overcast days, the Qi is cold; cold causes blood to congeal and become sluggish; congestion and slowness result in a bluish-black complexion. These are all instances of such correspondence. A complexion that responds to day/night and clear/overcast conditions is normal; one that does not respond is pathological.
Most diseases manifest as: lucid in the morning, peaceful during the day, aggravated in the evening, and severe at night. The complexion should accordingly reflect this pattern of "morning lucidity, daytime peace, evening aggravation, nighttime severity." However, if a patient is lighter in the evening and heavier in the morning, or less severe at night and more severe during the day, this is not governed by the circulation of Wei Qi, but solely by the state of Zang Qi (Visceral Qi). In such cases, the disease worsens when encountering the element that conquers it (the "unconquered" or "so bu sheng") and improves when encountering the element it conquers (the "conquered" or "so sheng"). The "unconquered" refers to what conquers me; the "conquered" refers to what I conquer. Generally, a day is divided into four periods, corresponding to the Five Zang Organs. The Liver corresponds to Jia-Yi days, with hours Yin-Mao; the Heart corresponds to Bing-Ding days, with hours Si-Wu; the Lungs correspond to Geng-Xin days, with hours Shen-You; the Kidneys correspond to Ren-Gui days, with hours Hai-Zi; the Spleen corresponds to Wu-Ji days, with hours Chen-Xu-Chou-Wei. By combining the days and hours of the Five Zang Organs with the pathological complexions of these organs, one can deduce the principles of generation and conquest, observe the patterns of remission and exacerbation, and determine the timing of death or survival. All reasoning and judgment are derived from this.
Nevertheless, within a single day or even a single two-hour period, temperature and humidity may vary unevenly, and rain may fall unpredictably, leading to varying degrees of dominance and subordination among climatic factors. Furthermore, residences differ in warmth and coolness, and clothing varies in thermal properties. Illness may therefore become heavier or lighter, and complexion may increase or decrease due to these factors. Although these cannot be judged solely by day/night cycles, they can all be viewed through the lens of clear/overcast conditions. Ultimately, this requires the observer to pay close attention and keep these observations in mind.