经云、微妙在脉。不可不察。今察脉之精。莫过内经。内经于诊法甚详。于脉法甚约。自叔和脉经兴。而脉象繁为
二十四。撰出七表八里九道之名。以为诊脉之法。莫尽于此。不知名象愈繁。诊道愈莫准。将求精而愈失之也。夫脉为
胃气之本源。其阴阳精要。即相为对待。相去悬绝之间。而有甚精之察。固不必多名象以求之也。且诊脉求病。求其为
病之表里虚实寒热顺逆而已。故内经设脉。止于浮沉缓急大小滑涩八脉。特于对待微甚悬绝。着其相去之三等。而脉之
情变已察之极精。及仲景又兼以阴阳着脉为十。以浮大滑动数为阳。沉弱涩弦微为阴。而察阴阳之法。莫过于此。于是
诊脉之精。至此大备。何以言之。人之先天禀于阴阳。而阴阳复生于胃气。唯谷神兴。而营气足。故脉行焉。中涵先天
四时五脏之正。而养于胃气。以微见其间。是以脉常有神。而可诊以阴阳逆从之法。而阴阳逆从之法。必首诊其胃气。
以及五脏四时。诊胃气者。诊其力。诊五脏者。诊其神。诊四时者。诊其顺。何谓力。胃之在三阳搏而勿浮。在三阴搏
而勿沉。其为洪圆有力。而阴阳两和。是平胃脉也。四至而闰以太息为五至。于何有病。此谓有力。若胃气衰耗。则必
先见不搏而浮沉矣。何谓神。五脏以五神而主五行。则恒见微弦微钩微 微毛微石之平衡。所谓藏真也。此谓有神。过
则相凌。弱则受克。而脏神失。再过则真藏现矣。何谓顺。五脏以胃气各自主时而奉天令。故春肝夏心秋肺冬肾。如天
之被物生长化收藏。以一旺主时。而群藏从。毋得以错迕争见者。此谓以顺反顺则为逆矣。逆时则逆藏。并逆胃矣。是
三者病本之诊也。于是审其阴阳以别柔刚。而知其逆顺之所在。是以别于阳者。知病起时。别于阴者。知死生之期。此
诊之大源。不可不知也。嗣是乃有相去之三诊。则并于其病情而知之。一法为对待。如浮沉缓急大小滑涩。各为对待。
皆两不相侔。判然可识者也。一法为微甚。从对待而推之。或甚浮微浮。甚沉微沉之过不及。可以从容而知之也。一法
为悬绝。如太过之三倍四倍。不及之迥绝绝无之殊。此为关格。真藏出见。脉可察而辨也。辨其对待。以察生克。辨其
微甚。以察间甚。辨其悬绝。以察死生。而又参仲景之阴阳十脉。合而察之。前三法为经。后四法为纬。不待多脉之名
象。而死生顺逆之机。燎若指掌矣。
《内经》说：“脉理的奥妙在于脉象，不可不仔细诊察。”如今在诊脉的精微方面，没有超过《内经》的。《内经》对于诊法非常详尽，而对于脉法却十分简约。自从王叔和的《脉经》兴起后，脉象繁复为二十四种，撰写出“七表、八里、九道”的名称，认为诊脉的方法没有比这更完备的了。却不知道名称和形象越繁杂，诊脉的道理就越不准确，想要追求精准反而更加失之千里了。
脉是胃气的本源，其中的阴阳精要，是相互对待（相对）的。它们之间虽然相差悬殊，但有着极其精微的观察要点，本来就不必通过众多的名目和形象来寻求。况且诊脉是为了求病，只求辨明疾病的表里、虚实、寒热、顺逆罢了。所以《内经》设立脉法，只限于浮、沉、缓、急、大、小、滑、涩这八种脉象。特别在对待关系中，细微、严重、悬殊绝异这三种程度，标明了它们之间的差异，而脉的情状变化已经观察得极其精微了。
到了张仲景，又兼以阴阳将脉分为十种：以浮、大、动、滑、数为阳脉；以沉、弱、涩、弦、微为阴脉。而考察阴阳的方法，没有比这更完备的了。于是诊脉的精微之处，至此大大完备了。为什么这样说呢？人的先天禀赋源于阴阳，而阴阳又生于胃气。只有谷气旺盛，营气充足，脉才能运行。脉中蕴含先天的四时五脏的正气，并受胃气的滋养，从而微妙地显现出来。因此脉常有神气，可以用阴阳逆从的方法来诊察。而阴阳逆从的方法，必须首先诊察胃气，以及五脏和四时。
诊察胃气，是诊察其“力”；诊察五脏，是诊察其“神”；诊察四时，是诊察其“顺”。什么是“力”？胃气在三阳经搏动时不浮，在三阴经搏动时不沉，脉象洪圆有力，阴阳两相调和，这就是平和的胃脉。每呼吸四次，加上一次深长的叹息（太息），合为五次搏动，这种情况下有什么病呢？这就叫作有力。如果胃气衰耗，则必然先出现不搏动且或浮或沉的现象。
什么是“神”？五脏以五神主宰五行，所以恒常见到微弦、微钩、微 、微毛、微石五种脉象的平衡状态，这就是所谓的“脏真”，这就叫作有神。如果太过就会相互凌犯，不足就会受到克制，这样脏神就丧失了。如果再过度，就会出现真脏脉。
什么是“顺”？五脏凭借胃气各自主司一时，并奉行天令。所以春天肝旺，夏天心旺，秋天肺旺，冬天肾旺，就像天地覆盖万物，经历生长化收藏的过程。由一个脏腑旺盛主导时令，而其他脏腑随之顺应，不得有错乱违背、争现的情况。这就叫作顺。反之则为逆。逆时则逆藏，并逆胃气。这三者是疾病根本的诊察方法。
于是审察阴阳以辨别柔刚，从而知道逆顺所在。所以，别于阳者，知道病起之时；别于阴者，知道死生之期。这是诊脉的大源头，不可不知道。此后才有上述三种程度的诊察，即结合病情来知晓。一种方法是“对待”，如浮与沉、缓与急、大与小、滑与涩，各自互为对待，都不相同，判然可识。一种方法是“微甚”，从对待关系推演而来，或者过于浮而轻微浮，过于沉而轻微沉，有过与不及之分，可以从容知晓。一种方法是“悬绝”，如太过达到三倍、四倍，不及到迥然不同、绝无仅有，这属于关格证，真脏脉出现，脉象可以察辨。
辨明其对待关系，以察知生克；辨明其微甚程度，以察知病情的轻重间隔；辨明其悬殊绝异，以察知死生预后。再参合张仲景的阴阳十脉，综合察辨。前三种方法为经，后四种方法为纬，不需要众多的脉之名目和形象，死生顺逆的机理，就像指掌一样清晰明了了。
The *Classic* states: "The subtlety lies in the pulse; it must not be neglected." In terms of the precision of pulse diagnosis, none surpasses the *Inner Canon* (*Neijing*). The *Inner Canon* is very detailed regarding diagnostic methods, yet concise regarding pulse methods. Since Wang Shuhe's *Pulse Classic* (*Maijing*) emerged, pulse images became complicated into twenty-four types, with names such as "Seven Superficial," "Eight Interior," and "Nine Dao" formulated, under the belief that no diagnostic method could be more complete than this. However, they did not realize that the more numerous the names and images, the less accurate the principles of diagnosis become; seeking precision results in greater deviation.
The pulse is the root source of Stomach Qi (Stomach Energy). Its essential Yin and Yang are mutually opposing and complementary. Although there is a vast difference between them, there exists an extremely subtle point of observation; it is unnecessary to seek them through numerous names and images. Furthermore, diagnosing the pulse to identify disease involves only distinguishing the exterior and interior, deficiency and excess, cold and heat, and favorable and unfavorable patterns. Therefore, the *Inner Canon* establishes only eight pulse types: Floating (Fu), Sinking (Chen), Slow (Huan), Rapid (Ji), Large (Da), Small (Xiao), Slippery (Hua), and Choppy/Rough (Se). It specifically highlights three degrees of difference within these opposing pairs—subtle (Wei), severe (Shen), and extreme/distant (Xuanjue)—to indicate their disparities, thereby observing the variations of the pulse with utmost precision.
Later, Zhang Zhongjing further categorized pulses into ten based on Yin and Yang: Floating, Large, Wiry/Active (Dong), Slippery, and Rapid are Yang pulses; Sinking, Weak, Choppy, String-taut (Xian), and Micro (Wei) are Yin pulses. This method of examining Yin and Yang is unparalleled. Thus, the precision of pulse diagnosis was greatly perfected at this stage. Why is this so? Human innate endowment originates from Yin and Yang, which in turn are generated by Stomach Qi. Only when Gu Shen (Grain Spirit/Nutritive Essence) flourishes does Ying Qi (Nutritive Qi) become sufficient, allowing the pulse to circulate. The pulse contains the upright Qi of the four seasons and five Zang organs from the congenital state, nourished by Stomach Qi, subtly manifesting therein. Hence, the pulse always possesses Shen (Spirit/Vitality), allowing diagnosis via methods of Yin-Yang reversal and adherence. The method of Yin-Yang reversal and adherence must first examine Stomach Qi, followed by the Five Zang organs and Four Seasons.
Examining Stomach Qi means examining its "Li" (Force); examining the Five Zang organs means examining their "Shen" (Spirit); examining the Four Seasons means examining their "Shun" (Harmony/Following). What is "Li"? When Stomach Qi pulses in the Three Yang channels, it should not be floating; when pulsing in the Three Yin channels, it should not be sinking. It should be full, round, and forceful, with Yin and Yang harmoniously balanced; this is the Ping (Peaceful/Normal) Stomach Pulse. With four beats per respiration cycle, plus one deep sigh (Tai Xi) making five beats, what disease would exist? This is called having force. If Stomach Qi declines and dissipates, it will first show signs of lacking force, appearing either floating or sinking.
What is "Shen"? The Five Zang organs govern the Five Elements via the Five Spirits. Thus, one constantly sees a balance of slightly Wiry (Xian), slightly Hooked (Gou), slightly , slightly Hairy (Mao), and slightly Stone-like (Shi) pulses. This is referred to as "Zang Zhen" (True State of the Zang), which is called having Shen. If excessive, they invade each other; if deficient, they are overcome by others, causing the loss of Zang Shen. If this continues, the True Zang Pulse appears.
What is "Shun"? The Five Zang organs, relying on Stomach Qi, each govern a season and obey Heavenly commands. Thus, Liver dominates Spring, Heart Summer, Lung Autumn, and Kidney Winter, mirroring Heaven covering all things through growth, flourishing, transformation, harvest, and storage. One organ dominates its season while the others follow suit, without disorder or contradiction. This is called Shun. Reversing this leads to Ni (Reversal). Reversing the season reverses the Zang, and also reverses Stomach Qi. These three constitute the diagnosis of the root of disease.
Thus, by examining Yin and Yang to distinguish soft and hard, one knows the location of reversal and harmony. Therefore, distinguishing from Yang reveals the onset of disease; distinguishing from Yin reveals the timing of death or life. This is the great source of diagnosis and cannot be ignored. Subsequently, the three degrees of difference mentioned above are applied to understand the disease condition. One method is "Duì Dài" (Opposition/Pairing), such as Floating vs. Sinking, Slow vs. Rapid, Large vs. Small, Slippery vs. Choppy. Each pair opposes the other, being distinct and recognizable. Another method is "Wei Shen" (Subtlety and Severity), deduced from opposition; for example, excessively floating versus slightly floating, or excessively sinking versus slightly sinking, indicating excess or deficiency, which can be understood calmly. A third method is "Xuan Jue" (Extreme Distance/Absence), such as exceeding by three or four times (excess) or being completely absent (deficiency). This indicates Guan Ge (Gate and Grid syndrome) and the appearance of True Zang Pulses, which can be observed and distinguished.
By distinguishing opposition, one observes generation and restriction; by distinguishing subtlety and severity, one observes the interval and severity of illness; by distinguishing extreme distance, one observes life and death. Combining this with Zhang Zhongjing’s Ten Yin-Yang Pulses creates a comprehensive examination. The first three methods serve as the warp (Jing), and the latter four as the weft (Wei). Without needing numerous pulse names and images, the mechanisms of life, death, favorability, and unfavorability become clear as if looking at one's palm.