《素问·阴阳别论》帝曰∶人有四经十二从，何谓？岐伯曰∶四经应四时，十二从应十二月，十二月应
十二脉。脉有阴阳，知阳者知阴，知阴者知阳。凡阳有五，五五二十五阳。所谓阴者，真脏也，见则为败，败
必死矣。所谓阳者，胃脘之阳也。别于阳者，知病处也；别于阴者，知死生之期。三阳在头，三阴在手，所
谓一也。别于阳者，知病忌时；别于阴者，知死生之期。谨熟阴阳，无与众谋。
四经应四时者，肝经应春，心经应夏，肺经应秋，肾经应冬，脾土应四季，在其中矣。十二从者，手足三
阴三阳，共十二经，相从周流于一身，如十二月之周行成一岁，终而复始也。脉理之要，别其阴阳，能知其阴，
即知其阳，能知其阳，即知其阴。何也？盖阴阳之气相合，外行经络，内行脏腑，循环不已，而五脏皆禀胃
脘阳和之气，其一脏遍含五脏之胃阳，故五五有二十五阳。脏为阴，腑为阳，所以谓阴者，真脏孤阴之气也。
真脏脉现，则本元败，败必死矣。所以谓阳者，胃脘之阳也，胃为阳土，其能纳水谷，化精微，生气血者，实
由先天元阳蒸腾之力，故得阳生阴长，气血和平，而脉象柔缓调匀，是为胃气，故脉有胃气则生；若胃阳败，
则孤阴真脏之脉现，如弦钩毛石而但急强散乱，绝无和缓之气，则死矣。是故能别其胃肠之和否，可知其病处，
如弦多胃气少，病在肝之类也；能别其孤阴真脏脉，可知死生之期，如肝至悬绝急，十八日死之类也。三阳经
脉上头，三阴经脉止于手，而阴阳通贯周流则一也。故能知阳可以知阴，知阴可以知阳。辨其阳脉之太过不及，
可知病有宜忌之时，如春夏人迎微大为宜，反小为忌，秋冬微小为宜，反大为忌；辨其阴脉之逆顺，可知死生
之期，如肝病遇木旺时可生，遇金旺时则死之类。如是谨记熟悉阴阳生化、五行生克之理，则辨别自明，无须
与庸众谋议，徒滋惑乱也。
黄帝问道：人有“四经”和“十二从”，这是什么意思？岐伯回答说：“四经”对应四季，“十二从”对应十二月，十二月对应十二条经脉。脉象有阴有阳，懂得阳就懂得阴，懂得阴就懂得阳。凡是阳脉共有五种，五五相乘得二十五阳。所谓“阴”，指的是真脏脉，如果出现就是脏腑精气败坏，败坏必然导致死亡。所谓“阳”，指的是胃脘的阳气。能够辨别阳脉的人，就知道病位所在；能够辨别阴脉（真脏脉）的人，就知道死生的期限。三阳经脉上行至头部，三阴经脉止于手部，这就是所谓的“一”（统一规律）。能够辨别阳脉的人，知道疾病发作的禁忌时间；能够辨别阴脉的人，知道死生的期限。务必熟习阴阳的道理，不要与众人商议（以免被庸俗之见干扰）。
所谓“四经应四时”，是指肝经对应春季，心经对应夏季，肺经对应秋季，肾经对应冬季，脾土对应四季之中，贯穿其中。所谓“十二从”，是指手三阴、手三阳、足三阴、足三阳，共十二条经脉，相互随从周流全身，就像十二月循环运行构成一年一样，终而复始。脉理的要点在于辨别阴阳，能了解阴就能了解阳，能了解阳就能了解阴。为什么呢？因为阴阳之气相互结合，外行于经络，内行于脏腑，循环不已。五脏都禀受胃脘中阳和之气，每一脏都包含五脏共同的胃阳，所以有五五二十五阳。脏属阴，腑属阳，所以所说的“阴”，是指真脏孤阴之气。真脏脉出现，说明本元败坏，败坏必然死亡。所以所说的“阳”，是指胃脘的阳气。胃为阳土，它能受纳水谷，化生精微，产生气血，这实际上是由先天元阳蒸腾的力量所致，因此得以阳生阴长，气血平和，脉象柔缓调匀，这就是胃气，所以脉中有胃气则生；如果胃阳败坏，那么孤阴的真脏脉就会出现，如弦、钩、毛、石等脉象但表现为急强散乱，完全没有和缓之气，就会死亡。因此，能够辨别胃肠之气是否调和，就可以知道病位所在，例如弦脉多而胃气少，病在肝之类；能够辨别孤阴真脏脉，就可以知道死生的期限，例如肝脉至悬绝急，十八日死之类。三阳经脉上行至头，三阴经脉止于手，而阴阳贯通周流的道理是一致的。所以能知阳就可以知阴，知阴就可以知阳。辨别阳脉的太过或不及，可以知道疾病适宜与禁忌的时间，例如春夏季节人迎脉微大为适宜，反而小则为禁忌；秋冬季节微小为宜，反而大为禁忌；辨别阴脉的逆顺，可以知道死生的期限，例如肝病遇到木旺之时可生，遇到金旺之时则死之类。像这样谨记并熟悉阴阳生化、五行生克的道理，那么辨别自然明了，不需要与平庸大众商议，徒然增加困惑混乱。
The Yellow Emperor asked: "Humans have 'Four Meridians' and 'Twelve Conformities'. What does this mean?"
Qibo replied: "The Four Meridians correspond to the Four Seasons, the Twelve Conformities correspond to the Twelve Months, and the Twelve Months correspond to the Twelve Meridians. Pulse qualities have Yin and Yang; knowing Yang means knowing Yin, and knowing Yin means knowing Yang. There are five types of Yang pulses, and five times five make twenty-five Yangs. The so-called 'Yin' refers to the Zang-Organ Pulse (True Visceral Pulse); when it appears, it indicates failure, and failure inevitably leads to death. The so-called 'Yang' refers to the Yang Qi of the Stomach Chamber. One who can distinguish Yang knows the location of the disease; one who can distinguish Yin knows the period of life or death. The Three Yang Meridians ascend to the head, and the Three Yin Meridians terminate at the hands; this is what is meant by 'One' (unity). One who distinguishes Yang knows the time contraindications for the disease; one who distinguishes Yin knows the period of life or death. Be diligent in mastering Yin and Yang, and do not consult with the masses."
Regarding "The Four Meridians corresponding to the Four Seasons," the Liver Meridian corresponds to Spring, the Heart Meridian to Summer, the Lung Meridian to Autumn, the Kidney Meridian to Winter, and the Spleen Earth corresponds to the middle of the four seasons, permeating them all. Regarding "The Twelve Conformities," these are the Hand Three Yin, Hand Three Yang, Foot Three Yin, and Foot Three Yang, totaling twelve meridians. They follow each other in circulation throughout the body, just as the twelve months cycle through to form a year, ending and beginning again. The essence of pulse theory lies in distinguishing Yin and Yang; understanding Yin allows one to understand Yang, and understanding Yang allows one to understand Yin. Why? Because the Qi of Yin and Yang combines, circulating externally in the meridians and internally in the zang-fu organs without cease. All five zang organs receive the harmonious Yang Qi of the stomach chamber. Each organ contains the stomach Yang common to all five, hence five times five equals twenty-five Yangs. Zang organs are Yin, and fu organs are Yang. Therefore, the "Yin" mentioned refers to the isolated Yin Qi of the true visceral state. When the True Visceral Pulse appears, the root vitality fails, and failure inevitably leads to death. Thus, the "Yang" mentioned refers to the Yang Qi of the stomach chamber. The Stomach is Yang Earth; its ability to receive food and water, transform essences, and generate Qi and Blood is actually due to the steaming power of congenital Primordial Yang. This allows Yang to generate and Yin to grow, resulting in harmonious Qi and Blood, and a pulse that is soft, slow, regular, and even—this is called Stomach Qi. Therefore, if the pulse has Stomach Qi, there is life; if Stomach Yang fails, the isolated Yin True Visceral Pulse appears. For example, pulses such as String-like (Xian), Hook-like (Gou), Feather-like (Mao), or Stone-like (Shi) may appear but manifest as rapid, strong, scattered, and chaotic, completely lacking any harmonious quality, leading to death. Thus, by distinguishing whether the harmony of the stomach and intestines is intact, one can know the location of the disease; for instance, if the String-like quality is excessive and Stomach Qi is scant, the disease is in the Liver. By distinguishing the isolated Yin True Visceral Pulse, one can know the period of life or death; for instance, if the Liver pulse becomes suspended, extreme, and rapid, death occurs in eighteen days. The Three Yang meridian channels ascend to the head, and the Three Yin meridian channels terminate at the hands, yet the principle of Yin and Yang penetrating and circulating uniformly remains the same. Therefore, knowing Yang allows one to know Yin, and knowing Yin allows one to know Yang. By distinguishing the excess or deficiency of Yang pulses, one can know the favorable and unfavorable times for the disease; for example, in spring and summer, a slightly larger Renying (Carotid) pulse is favorable, while a smaller one is unfavorable; in autumn and winter, a small and fine pulse is favorable, while a large one is unfavorable. By distinguishing the reversal or smoothness of Yin pulses, one can know the period of life or death; for instance, in Liver diseases, life is possible when Wood Qi is prosperous, but death occurs when Metal Qi is prosperous. By diligently remembering and familiarizing oneself with the principles of Yin-Yang generation/transformation and Five Elements mutual generation/restriction, discrimination will naturally become clear, eliminating the need to consult with mediocre crowds, which would only add confusion.