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*Equiseti Herba* (Mu Zei) is produced in the commanderies of Qinzhou, Longzhou, Huazhou, and Chengzhou. It is also found in areas near water sources. The seedlings grow to about one chi in height, growing in clusters and straight upward. Each plant has a single stem without flowers or leaves, with internodes approximately one cun long and hollow in the center. The stems are rough and涩 (astringent/coarse), resembling *Ephedrae Herba* (Mahuang, 麻黄) but slightly thicker. It does not wither in winter. It is harvested in the fourth month. (Li Shizhen's commentary)

[Stem]
The taste is sweet with a slight bitterness, and the temperature is warm. Its texture is hollow and light, possessing ascending and floating properties. It enters the blood aspect of the Foot Jueyin Liver Meridian and Foot Shaoyang Gallbladder Meridian, and also enters the Foot Taiyin Spleen Meridian. It mainly treats eye diseases, removes corneal opacities (pterygium/membranes), stops tearing, eliminates accumulations, benefits the liver and gallbladder, treats intestinal wind bloody dysentery, as well as continuous menstruation in women, metrorrhagia with red and white discharge, dispels wind-dampness pain, and treats rectal prolapse. After removing the nodes and roasting over fire, it induces sweating easily. (Zhu Danxi's commentary) *Equiseti Herba* resembles *Ephedrae Herba* (Mahuang, 麻黄) in shape and nature; therefore, it can induce sweating and release the muscle layer, ascend and disperse wind-dampness, and treat various blood disorders of the eyes. When combined with *Bovis Cornu* (Niujiao, 牛角) and *Moschus* (Shexiang, 麝香), it treats chronic persistent dysentery (Xixi Ji). When combined with *Haematitum* (Yuyuliang, 禹余粮), *Angelicae Sinensis Radix* (Danggui, 当归), and *Chuanxiong Rhizoma* (Chuanxiong, 川芎), it treats metrorrhagia with red and white discharge. When combined with *Auricula Judaea* (Sanger, 桑耳), it treats intestinal wind bleeding. When combined with *Sophorae Fructus* (Huai Zi, 槐子) and *Immature Bitter Orange* (Zhishi, 枳实), it treats hemorrhoidal bleeding. When combined with *Gigantochloa Balcooa Flower* (Gu Jing Cao, 谷精草), *Cassiae Semen* (Jueming Zi, 决明子), *Tribulus Fruit* (Bajili, 白蒺藜), and *Cicada Molt* (Chan Hua, 蝉花), it treats chronic eye diseases causing opacity and obstruction. When combined with *Sophorae Tonkinensis Fruit* (Huai Jiao Zi, 槐角子), *Xanthii Fructus* (Canger Zi, 苍耳子) [prepared by keeping the nature], *Sanguisorbae Radix* (Diyu, 地榆), and *Rubia Cordifolia Radix* (Qian Gen, 茜根), it treats chronic hemorrhoidal bleeding lasting for years. For severe metrorrhagia and blood qi pain that have persisted for a long time without cure, use *Mu Zei San* (Wood Horsetail Powder) as the main formula: take two liang of *Equiseti Herba* (Mu Zei) and *Immature Bitter Orange* (Zhike, 枳壳), one liang of *Zingiberis Rhizoma Recens* (Ganjiang, 干姜), and half a qian of *Rhei Radix et Rhizoma* (Dahuang, 大黄); stir-fry them until blackened while preserving their nature, then grind into powder. Use *Mu Zei San*: one liang each of *Equiseti Herba* (Mu Zei) and *Cyperi Rhizoma* (Xiangfu, 香附), and half a liang of *Natrii Sulfas* (Puxiao, 朴硝). Decoct with one cup of wine if the material is dark/black, or one cup of water if it is red/cherry-colored. Take the dregs and liquid together, twice daily. If there is pain below the umbilicus, add *Frankincense* (Ruxiang, 乳香). Avoid raw, cold, hard foods, pork, fish, greasy foods, alcohol, and wheat products.

[Discussion]
*Equiseti Herba* is hollow and grows straight upward, indicating yang penetrating through yin, allowing wind to rise and reach everywhere. Having many nodes after enduring winter indicates that yang can transform yin, and the qi does not exceed the nodes. Because dampness cannot be transformed, it returns to cause disease in the liver. However, this is what *Equiseti Herba* can achieve. For conditions where yang fails to be transformed by yin, treatment should address the root cause. As for stopping eye tearing, it is due to blood failing to transform properly and being affected by wind; ultimately, it remains within the category of blood disorders. Eye diseases caused by anger, or sudden redness, swelling, and pain due to summer-heat injuring the blood, are not suitable for treatment with this herb. (Zhong Chun's commentary)

[Processing]
Remove the nodes. Soak in urine from a healthy boy overnight, then dry by baking before use.