Library

Bitter and sour. This text mentions only the flavor and omits the nature, which leads to suspicion of missing text. Subsequent instances where the nature is not mentioned should follow this pattern. It primarily treats Wei Bi (flaccidity syndrome and bi-syndrome caused by cold-dampness), spasm and contracture of the four limbs, and knee pain with inability to flex or extend, all of which are attributed to the merit of relaxing sinews and promoting blood circulation. It expels blood qi and breaks up blood stasis. For injuries caused by fire-heat leading to tissue rot, it clears heat. It induces abortion, which is due to its ability to direct blood qi downward. Long-term use makes the body light and enhances resistance to aging, reflecting the merit of harmonizing blood.

This deduces the nature from the form. Generally, the roots of all plants grow horizontally, but the root of Achyranthes Bidentata (Niuxi, 牛膝) grows vertically downward. It is long, slender, and tough, closely resembling human sinews; therefore, it can relax sinews and unblock collaterals, direct blood downward, and descend qi, serving as a forerunner among drugs that have a descending action. Sinews belong to the Liver, and the Liver stores blood. Any drug that can relax sinews can also treat blood disorders; thus, it is also a substance that promotes the free flow of blood vessels.

Bitter and neutral. It primarily treats conditions of the heart and abdomen, removes knotted qi in the intestines and stomach. Being of a light and ascending nature, it can disperse stagnant qi in the intestines and stomach. It disperses accumulations of fluids and qi, and resolves stagnation in the intestines and stomach. It drives out pathogenic factors of cold and heat, eliminating external pathogens from the meridians. It pushes out the old and brings forth the new. Speaking generally of the above three points, when pathogens are expelled, healthy qi recovers. Long-term use makes the body light, brightens the eyes, and benefits essence. Since no pathogens can remain, healthy qi flows freely, hence this effect.

Chai Hu (Bupleuri Radix, 柴胡) is a medicine for the intestines and stomach. Observing the therapeutic effects recorded in the classic, they all primarily target the intestines and stomach. Because its flavor and nature are light and clear, it can regulate stagnant qi within the stubborn earth (Spleen/Stomach); thus, its efficacy is as described. Only wood can loosen soil. Previous scholars identified it solely as a Shaoyang (Lesser Yang) channel drug, knowing its branch but not its root. Why does Zhang Zhongjing's Xiao Chai Hu Tang (Minor Bupleurum Decoction) specifically treat Shaoyang disease using it as the chief ingredient? According to the sequence of transmission in Shanghan (Cold Damage), it first transmits to Taiyang (Greater Yang), then to Yangming (Bright Yang), and finally to Shaoyang. Although Shaoyang is located between Taiyang and Yangming anatomically, in terms of transmission order, it follows Yangming. Having passed through Yangming, it enters Shaoyang; thus, Shaoyang is actually internal to Yangming. From the perspective of location, Shaoyang is between Taiyang and Yangming; but from the perspective of the pathway of entry, Shaoyang is inside Taiyang and Yangming. Therefore, treating Shaoyang has nothing to do with Taiyang but is close to Yangming. For example, Ban Xia (Pinelliae Rhizoma) and Gan Cao (Glycyrrhizae Radix et Rhizoma) in Xiao Chai Hu Tang are both medicines for Yangming. Precisely because of this, its flavor and nature must be light, clear, and dispersing so that pathogens can penetrate the "earth" layer and exit. Understanding this clarifies Zhang Zhongjing's rationale for using Chai Hu and confirms that Chai Hu is a medicine for the intestines and stomach.