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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.