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脉之不病。其神不言。当自有也。脉既病。当求其中神之有与无焉。谓如六数七极热也
脉
中有力。即有神也。三迟二败寒也。脉中有力。即有神也。热则有神当泄其热。则神在焉。
寒则有神当去其寒。则神在焉寒热之脉无力无神。将何药而泄热去寒乎。苟不知此而遽泄去
之。将何根据以生。所以十亡八九。故经曰。脉者血气之先。又云。血气者人之神。可以不谨
养乎。不可不察其有无乎。
假令治病无问伤寒蓄血结胸发黄等病诸证。并一切杂证。各当于六经中求责之谓如发黄
证
或头痛腰脊强恶寒。即太阳证也。或身热。目疼鼻干不得卧。即有阳明证也。余皆仿此。
谓如手阳明流入足阳明是上流下也。本非足经病当于手经中求之。是知治足经者非也。
亦有下
而流上者。其余诸经相实通者皆然。更有支别流入者亦有同邻而病者。合为表里者邻也。亦
有夫妇各相传受者。甲传巳之类。脾传胃之类亦是。皆当求责之。凡言虚实。皆当于子母中
求责之。
假令腹痛。桂枝加芍药大黄。桂枝加大黄何为。不只用芍药大黄之属。却于（桂枝汤）内
加
之。大抵治病必求其责。知从太阳中来。故以太阳为本也。又如结胸证。自高而下。脉浮者
不可下。故先用麻黄汤解表已。脉沉然后以陷胸汤下之。是亦求其本也。至于蓄血下焦血结
膀胱是亦从太阳中来。侵尽无形之气。乃侵膀胱中有形血也。
四正脉损伤的图示
脉象没有病变时，其中的“神”（指脉中蕴含的生命活力与胃气）不言自明，自然存在。脉象一旦生病，就应当探究其中“神”的有或无。比如脉象数（快）七至为极数，主热证；若脉中有力，就是有“神”。脉象迟（慢）三至、二至为败脉，主寒证；若脉中有力，也是有“神”。热证而有“神”，应当清泄其热，那么“神”就能留存。寒证而有“神”，应当去除其寒，那么“神”就能留存。如果寒热之脉无力且无“神”，还用什么样的药去清泄热邪、驱除寒邪呢？如果不明白这个道理而贸然使用攻下法去泄热，身体将凭借什么来维持生机？所以死亡率高达八九成。因此《内经》说：“脉是血气运行的先导。”又说：“血气就是人的精神所在。”能不谨慎调养吗？不能不仔细考察其“神”的有无啊。
假设治疗疾病，无论是伤寒、蓄血、结胸、发黄等病证，还是所有杂证，都应当在六经（太阳、阳明、少阳、太阴、少阴、厥阴）中寻求病因和病位。例如发黄证，如果出现头痛、腰脊僵硬、恶寒，这就是太阳经证。如果出现身热、眼睛疼痛、鼻干、无法安卧，这就是阳明经证。其余情况都仿照此例。
比如手阳明大肠经的病邪流入足阳明胃经，这是由上往下流注。这本来不是足经本身的病，应当在手经中寻求治疗，这样就知道只治疗足经是错误的。也有由下往上流注的情况。其余各经相互传变通达的道理都是如此。还有分支别络流入的情况，也有相邻经络同时发病的情况。“邻”是指互为表里的经络。也有像夫妻一样相互传受的情况，如甲木传巳火之类，脾土传胃土之类也是。这些都应当仔细推求。凡是谈到虚实，都应当在子母（五行相生关系中的母子）关系中寻求病因。
假设遇到腹痛，用桂枝加芍药大黄汤。为什么只用桂枝加大黄？为什么不单独使用芍药、大黄这类药物，而是在桂枝汤的基础上加入它们？大抵治病必须探求根本。知道病邪是从太阳经传来的，所以以太阳经为本。又比如结胸证，病势由高向低发展，脉象浮的不可用攻下法，所以先用麻黄汤解表，待脉象转为沉后，再用陷胸汤攻下。这也是探求根本的方法。至于蓄血证，下焦血结于膀胱，这也是从太阳经传来，先侵扰了无形之气，进而侵入膀胱中有形的血液。
Diagram of Injury to the Four Correct Pulses
When the pulse is not diseased, its Shen (vital spirit/life force reflected in the pulse) speaks for itself and exists naturally. Once the pulse becomes diseased, one must investigate whether the Shen is present or absent within it. For instance, a rapid pulse (Shu, 数) reaching seven beats per breath cycle indicates extreme heat; if there is strength within the pulse, this constitutes having Shen. A slow pulse (Chi, 迟) at three or two beats per breath cycle indicates a failing pulse and cold; if there is strength within the pulse, this also constitutes having Shen. In cases of heat with Shen, one should clear and drain the heat, thereby preserving the Shen. In cases of cold with Shen, one should dispel the cold, thereby preserving the Shen. If the pulses of heat and cold are weak and lack Shen, what medicine can be used to clear heat and dispel cold? If one does not understand this and rashly employs purgation to drain heat, on what basis will life be sustained? Consequently, eight or nine out of ten patients die. Thus, the Classic states: "The pulse is the precursor of Qi and Blood." It also says: "Qi and Blood constitute the Shen of humanity." Can one fail to carefully nourish them? One cannot but examine their presence or absence.
Suppose treating diseases, regardless of whether they are Cold Damage (Shanghan, 伤寒), blood stasis (Xuxue, 蓄血), chest binding (Jiexiong, 结胸), jaundice (Fahuang, 发黄), or any other miscellaneous conditions, one must seek the cause and location within the Six Channels (Liu Jing, 六经). For example, in a case of jaundice, if there is headache, stiffness of the waist and spine, and aversion to cold, this is a Taiyang channel syndrome. If there is body heat, eye pain, nasal dryness, and inability to lie down, this is a Yangming channel syndrome. The rest follow this pattern.
For instance, pathogen flowing from the Hand-Yangming Large Intestine channel to the Foot-Yangming Stomach channel represents downward transmission. This is originally not a disease of the Foot channel, so treatment should be sought in the Hand channel; thus, knowing that treating only the Foot channel is incorrect. There are also cases of upward transmission. The principles of mutual transmission and connection among other channels are similar. There are also cases of branch collateral infiltration, or simultaneous disease in adjacent channels. "Adjacent" refers to channels that are exterior-interior pairs. There are also cases of transmission akin to husband and wife, such as Jia Wood transmitting to Si Fire, or Spleen Earth transmitting to Stomach Earth. All these must be investigated. Whenever discussing deficiency and excess, one must seek the cause within the Mother-Child (Zimu, 子母) relationships (of the Five Elements).
Suppose encountering abdominal pain, one uses Guizhi Jia Shaoyao Dahuang Tang (Cinnamon Twig Decoction Modified with Paeonia and Rhubarb). Why use Guizhi plus Dahuang? Why not simply use agents like Shaoyao and Dahuang alone, but instead add them to Guizhi Tang? Generally, treating disease requires seeking its root. Knowing that the pathogen originated from the Taiyang channel, one takes the Taiyang channel as the root. Similarly, in cases of chest binding, where the pathology descends from high to low, if the pulse is floating, purgation is contraindicated. Therefore, one first uses Mahuang Tang (Ephedra Decoction) to release the exterior; once the pulse becomes deep, one then uses Xianxiong Tang (Sinking Chest Decoction) to purge. This too is seeking the root. As for blood stasis, where blood coagulates in the lower jiao and bladder, this also originates from the Taiyang channel, first invading the formless Qi, and subsequently invading the formed blood within the bladder.