四逆者。四肢逆而不温也。四肢者。诸阳之本。阳气不足。阴寒加之。阳气不相顺接。
是致手足不温。而成四逆也。此汤申发阳气。却散阴寒。温经暖肌。是以四逆名之。
甘草味甘平。内经曰。寒淫于内。治以甘热。却阴扶阳。必以甘为主。是以甘草为君。
干姜味辛热。内经曰。寒淫所胜。平以辛热。逐寒正气。必先辛热。是以干姜为臣。附
子味辛大热。内经曰。辛以润之。开发腠理。致津液通气也。暖肌温经。必凭大热。是
以附子为使。此奇制之大剂也。四逆属少阴。少阴者肾也。肾肝位远。非大剂则不
能达。内经曰。远而奇偶。制大其服。此之谓也。
甘草（君二两） 干姜（臣一两半） 附子（使一枚生用去皮八片）
上三味。以水三升。煮取一升二合。去渣。分温再服。强人可大附子一枚。干姜三
两。
真武北方水神也。而属肾。用以治水焉。水气在心下。外带表而属阳。必应发散。故
治以真武汤。青龙汤主太阳病。真武汤主少阴病。少阴肾水也。此汤可以和之。真
武之名得矣。茯苓味甘平。白术味甘温。脾脾恶。腹有水气。则脾不治。脾欲缓。急食
甘以缓之。渗水缓脾。必以甘为主。故以茯苓为君。白术为臣。芍药味酸微寒。生姜
味辛温。内经曰。湿淫所胜。佐以酸辛。除湿正气。是用芍药生姜酸辛为佐也。附子
味辛热。内经曰。寒淫所胜。平以辛热。温经散温。是以附子为使也。水气内渍。至于
散则所行不一。故有加减之方焉。若咳者加五味子细辛干姜。咳者水寒射肺也。
肺气逆者。以酸收之。五味子酸而收也。肺辛寒。以辛润之。细辛干姜辛而润也。若小便利者。去茯苓。茯苓专渗泄者
也。若下利者去芍药。加干姜。酸之性泄。去芍药
以酸泄也。辛之性散。加干姜以散寒也。呕者去附子。加生姜。气上逆则呕。附子补
气。生姜散气。两不相损。气则顺矣。增损之功。非大智孰能贯之。
茯苓（君三两） 白术（臣二两） 芍药（佐三两） 生姜（佐二两切） 附子（使一枚泡去皮脐作八片）
上五味。以水八升。煮取三升。去渣。温服七合。日三服。
Si Ni (Four Reversals) refers to the condition where the four limbs are cold and not warm. The four limbs are the root of all Yang meridians. When Yang Qi is insufficient and Yin-Cold pathogenic factors invade, causing Yang Qi to fail in connecting smoothly with the extremities,
the hands and feet become cold, resulting in the Si Ni syndrome. This decoction aims to promote the emergence of Yang Qi, dispel Yin-Cold, warm the meridians, and warm the muscles and skin; hence it is named "Si Ni Tang" (Four Reversals Decoction).
Gancao (Licorice Root) has a sweet flavor and neutral nature. The *Neijing* states: "When Cold invades internally, treat with Sweet-Hot substances." To suppress Yin and support Yang, one must primarily use Sweet herbs; therefore, Gancao is used as the Sovereign herb.
Ganjiang (Dried Ginger) has a pungent flavor and hot nature. The *Neijing* states: "When Cold prevails, pacify with Pungent-Hot substances." To drive out Cold and restore healthy Qi, one must first use Pungent-Hot herbs; therefore, Ganjiang is used as the Minister herb.
Fuzi (Prepared Aconite Lateralis Radix) has a pungent flavor and great hot nature. The *Neijing* states: "Pungent moistens, opens the interstices, promotes the flow of fluids, and unblocks Qi." To warm the muscles and unblock the meridians, one must rely on Great Hot substances; therefore, Fuzi is used as the Envoy herb. This is a large-dose prescription with an odd-numbered composition. Si Ni Tang belongs to the Shaoyin disease category, and Shaoyin corresponds to the Kidney. The positions of the Kidney and Liver are deep and distant; unless the dose is large, the medicinal power cannot reach the site of disease. The *Neijing* states: "When the disease location is distant and the prescription involves odd/even variations, increase the dosage." This is what is meant.
Gancao (Sovereign, 2 liang) Ganjiang (Minister, 1.5 liang) Fuzi (Envoy, 1 piece, raw, peeled, cut into 8 slices)
Take these three ingredients, add 3 sheng of water, boil to obtain 1.2 sheng of liquid, remove the dregs, and divide into two doses for warm administration. For robust individuals, use 1 large Fuzi and 3 liang of Ganjiang.
Zhenwu represents the Water Deity of the North and corresponds to the Kidney in Five Elements theory; here it is used to treat Water-Qi disorders. Water-Qi stagnates below the heart (epigastrium), extends outward to involve the exterior (Yang aspect), and thus requires dispersing methods; therefore, Zhenwu Tang is used to treat it. Qinglong Tang treats Taiyang disease, while Zhenwu Tang treats Shaoyin disease. Shaoyin corresponds to Kidney Water, and this decoction harmonizes Kidney Water, which gives rise to the name Zhenwu.
Fuling (Poria) has a sweet flavor and neutral nature; Baizhu (Atractylodis Macrocephalae Rhizoma) has a sweet flavor and warm nature. The Spleen dislikes dampness; when Water-Qi accumulates in the abdomen, the Spleen's transport function fails. The Spleen desires relaxation, urgently requiring Sweet foods to soothe it. To leach out water and soothe the Spleen, one must primarily use Sweet herbs; therefore, Fuling is used as the Sovereign herb, and Baizhu as the Minister herb.
Shaoyao (White Peony Root) has a sour flavor and slightly cold nature; Shengjiang (Fresh Ginger Rhizome) has a pungent flavor and warm nature. The *Neijing* states: "When Dampness prevails, assist with Sour-Pungent substances." To eliminate Dampness and restore healthy Qi, Shaoyao and Shengjiang are used as Assistant herbs due to their Sour and Pungent properties.
Fuzi has a pungent flavor and hot nature. The *Neijing* states: "When Cold prevails, pacify with Pungent-Hot substances." To warm the meridians and scatter Cold, Fuzi is used as the Envoy herb. Internal infiltration of Water-Qi leads to varied manifestations as it spreads; thus, there are modified prescriptions.
If coughing occurs, add Wuweizi (Schisandra Fruit), Xixin (Asarum Root), and Ganjiang. Coughing results from Cold-Water attacking the Lung. When Lung Qi rebels upward, it should be astringed with Sour substances. Wuweizi is Sour and astringent. The Lung prefers Pungent-Moistening; use Pungent herbs to moisten the Lung. Xixin and Ganjiang are Pungent and moistening.
If urination is free, remove Fuling, as Fuling specializes in leaching and draining.
If diarrhea occurs, remove Shaoyao and add Ganjiang. The nature of Sour tends toward purging/draining; removing Shaoyao avoids Sour-induced purging. The nature of Pungent tends toward dispersing; adding Ganjiang disperses Cold.
If vomiting occurs, remove Fuzi and add Shengjiang. Upward rebellion of Qi causes vomiting. Fuzi tonifies Qi, while Shengjiang disperses Qi; together they do not harm each other, allowing Qi to flow smoothly. The efficacy of adding and subtracting herbs—can anyone of great wisdom comprehend it fully?
Fuling (Sovereign, 3 liang) Baizhu (Minister, 2 liang) Shaoyao (Assistant, 3 liang) Shengjiang (Assistant, 2 liang, sliced) Fuzi (Envoy, 1 piece, processed, peeled, navel removed, cut into 8 slices)
Take these five ingredients, add 8 sheng of water, boil to obtain 3 sheng of liquid, remove the dregs, take 7 ge per dose warm, three times daily.