牛膝∶味甘微酸，性微温。原为补益之品，而善引气血下注，是以用药欲其下行者，恒以之为引经。故善
治肾虚腰疼、腿疼，或膝疼不能屈伸，或腿痿不能任地，兼治女子月闭血枯，催生下胎。又善治淋疼，通利
小便，此皆其力善下行之效也。然《名医别录》又谓其除脑中痛，时珍又谓其治口疮齿痛者何也？盖此等
证，皆因其气血随火热上升所致，重用牛膝引其气血下行，并能引其浮越之火下行，是以能愈也。愚因悟得此
理，用以治脑充血证，伍以赭石、龙骨、牡蛎诸重坠收敛之品，莫不随手奏效，治愈者不胜纪矣。为其性专下
注，凡下焦气化不固，一切滑脱诸证皆忌之。此药怀产者佳，川产者有紫、白两种色，紫者佳。
【附案】在辽宁时，曾治一女子，月信期年未见，方中重用牛膝一两，后复来诊，言服药三剂月信犹未
见，然从前曾有脑中作疼病，今服此药脑中清爽异常，分毫不觉疼矣。愚闻此言，乃知其脑中所以作疼者，血
之上升者多也。今因服药而不疼，想其血已随牛膝之引而下行，遂于方中加 虫五枚，连服数剂，月信果通。
友人袁××，素知医，时当季春，牙疼久不愈，屡次服药无效。其脉两寸甚实，俾用怀牛膝、生赭石各
一两，煎服后，疼愈强半，又为加生地黄一两，又服两剂，遂霍然全愈。
Niu Xi (Radix Achyranthis Bidentatae): Its flavor is sweet with a slight sourness, and its nature is slightly warm. Originally classified as a tonic herb, it excels at guiding Qi and Blood downward. Therefore, when prescribing herbs intended to act on the lower part of the body, it is frequently used as a guiding herb (Yin Jing Yao). Consequently, it is effective in treating lumbar pain and leg pain due to Kidney deficiency, knee pain accompanied by inability to flex or extend, or leg flaccidity preventing one from bearing weight. It also treats amenorrhea and blood depletion in women, and can induce labor and expel the fetus. Furthermore, it effectively treats painful urinary dysfunction (Lin syndrome) and promotes urination; all these effects stem from its potent downward-moving action. However, why does *Mingyi Bielu* (Classic of Famous Physicians) state that it eliminates pain in the brain, and why does Li Shizhen claim it treats mouth ulcers and toothache? This is because such conditions are caused by Qi and Blood rising along with Fire-Heat. By heavily utilizing Niu Xi to guide Qi and Blood downward, and to lead floating and hyperactive Fire downward, the conditions can be cured. I realized this principle and applied it to treat cerebral congestion syndrome. Combined with heavy, sinking, and astringent herbs such as Dai Zhe Shi (Hematitum), Long Gu (Os Draconis), and Mu Li (Concha Ostreae), it invariably produced immediate results, with countless cures recorded. Since its nature is specifically directed downward, it is contraindicated in any condition involving failure of Qi transformation in the Lower Jiao and all types of slipping and incontinence syndromes. The variety produced in Huaiqing is superior. The variety produced in Sichuan comes in purple and white colors, with the purple variety being better.
[Attached Case] While in Liaoning, I treated a female patient who had not menstruated for a year. In the prescription, I heavily utilized Niu Xi (one liang). She returned for follow-up, stating that after three doses, her menstruation still had not started. However, she noted that although she previously suffered from headaches, her head now felt exceptionally clear and free of pain upon taking this medicine. Hearing this, I deduced that the cause of her headache was excessive upward movement of Blood. Since the pain ceased after medication, I surmised that the Blood had descended following the guiding action of Niu Xi. I then added five Eupolyphaga seu Asiae (Biesong, 土鳖虫) to the formula. After several doses, her menstruation indeed became patent. My friend Yuan XX, who was knowledgeable in medicine, suffered from persistent toothache in late spring, unresponsive to repeated treatments. His radial pulses at both Cun positions were very full and forceful. I prescribed Huai Niu Xi (Radix Achyranthis Bidentatae) and Sheng Dai Zhe Shi (Hematitum) in equal amounts of one liang each. After decoction and ingestion, the pain diminished by more than half. I then added Sheng Di Huang (Radix Rehmanniae Preparata) one liang. After two more doses, he recovered completely.