【气味】
苦寒无毒。沉而降阴也。入足少阴经为足太阳引经之药。
【主治】
五脏肠胃中结热。利下窍。泻伏火。救肾水。治冲脉气逆不渴。而小便不通。得知
母滋阴降火。得苍术除湿清热。得细辛泻膀胱火。治口舌生疮。凡奉养太过。膏粱积热损伤
肾水。致膀胱久而干涸。小便不化。火逆上而为呕哕者。难经所谓关则不得小便。格则吐逆
者也。此宜以黄柏之苦寒泻燥以补水也。又热邪蓄于下焦血分。不渴而小便不通者。乃素问
所谓无阴则阳无以生。无阳则阴无以化。膀胱为州都之官。津液之脏。火客于水。则阳气不
升。此宜以黄柏之苦寒。抑火而升阳。而令阴阳互相生化也。故火有二。君火者。人火也。
心火也。可以湿伏。可以水灭。可以直折。故谓知母黄柏之属。为滋阴降火之对剂。若相火
者。天火也。龙雷之火也。阴火也。不可以水湿折之何也。龙雷之火。五六月而起发。九十
月而归藏。盖冬时阳气在水土之下。龙雷就其火气而居于下。夏时阴气在下。龙雷不能安其
身而出于上。若以黄柏之属降之。是欲括龙雷之势于浓阴骤雨之时也。可乎不可乎。唯太阳
一照。火自消灭。此则得水而炽。得火而灭之明验也。近时虚损及纵欲之人。用补阴药往往
以知母黄柏二味为君。日日服饵。降令太过。脾胃受伤。真阳暗损。精气不暖。致生他病。
岂知黄柏知母苦寒滑渗。久服有反从火犯之害。可不慎欤。明乎此而黄柏知母谓之降母以滋
阴可也。若竟曰滋阴降火。则矛盾之甚矣。
【气味】
味苦，性寒，无毒。药性沉降，属于阴。进入足少阴肾经，作为引导足太阳膀胱经药物的引经药。
【主治】
清除五脏和肠胃中的郁结之热。通利下窍（前阴）。泻除潜伏之火。挽救肾水（滋养肾阴）。治疗冲脉之气上逆但不口渴，且小便不通的症状。若配合知母使用，可滋阴降火；若配合苍术使用，可除湿清热；若配合细辛使用，可泻膀胱之火，治疗口舌生疮。凡是生活供养过于丰厚，因食用肥甘厚味积滞化热而损伤肾水，导致膀胱日久干涸，小便无法正常气化排出，火热之气上逆引起呕吐呃逆的，这正是《难经》所说的“关则不得小便，格则吐逆”的病证。这种情况适宜用黄柏的苦寒之性来泻燥以补充肾水。另外，若热邪蓄积在下焦血分，患者不口渴但小便不通，这是《素问》所说的“无阴则阳无以生，无阳则阴无以化”。膀胱被称为州都之官，是津液汇聚之脏。火邪客居水中，会导致阳气不能上升。这种情况适宜用黄柏的苦寒之性，抑制火势从而升发阳气，使阴阳互相生化。因此火分为两种：君火，即人火，也就是心火，可以用湿气伏制，用水熄灭，或用直折法清泻，所以认为知母、黄柏这类药物，是滋阴降火的对症良方。至于相火，是天火，也是龙雷之火、阴火，不可以用水湿来折服。为什么呢？龙雷之火，在五六月间发作，在九十月间潜藏。大概是因为冬季时阳气在水土之下，龙雷依附其火气而居于下位；夏季时阴气在下，龙雷无法安身而浮出于上。如果用黄柏这类药物来降伏它，就像是想在浓云骤雨之时强行遏制龙雷之势，这可以吗？不可以。只有太阳一照，火自然消灭。这是得水则炽盛、得火则熄灭的明证。近代虚损及纵欲之人，服用补阴药往往以知母、黄柏两味药为主药，日日服用，导致降泄太过，损伤脾胃，暗中损耗真阳，精气不再温暖，从而引发其他疾病。哪里知道黄柏、知母苦寒滑利渗泄，久服会有反而从火化犯上的危害，能不谨慎吗？明白了这一点，称黄柏、知母为“降母”以滋阴是可以的。如果竟说它们是“滋阴降火”，那就矛盾得很了。
[Flavor and Nature]
Bitter, cold, non-toxic. The medicinal property is sinking and descending, belonging to Yin. It enters the Foot-Shaoyin (Kidney) meridian and serves as a guiding herb for the Foot-Taiyang (Bladder) meridian.
[Indications]
It clears accumulated heat in the five Zang organs and the intestines and stomach. It promotes the free flow of the lower orifices. It drains latent fire and rescues Kidney Water (nourishes Kidney Yin). It treats rebellious Qi of the Chong vessel without thirst, accompanied by dysuria. When combined with Anemarrhenae Rhizoma (Zhimu, 知母), it nourishes Yin and descends fire; when combined with Atractylodis Rhizoma (Cangzhu, 苍术), it removes dampness and clears heat; when combined with Asari Radix (Xixin, 细辛), it drains Bladder fire and treats sores in the mouth and tongue. In cases where excessive indulgence in rich food leads to accumulated heat damaging Kidney Water, causing the Bladder to become dry over time, resulting in the failure of urine transformation, and fire rebelling upward causing vomiting and hiccups, this corresponds to the "Guan" (closure leading to inability to urinate) and "Ge" (regurgitation leading to vomiting) described in the *Nan Jing* (Classic of Difficult Issues). This condition is suitable for treatment with the bitter-cold nature of Phellodendri Cortex (Huangbai, 黄柏) to drain dryness and replenish water. Furthermore, if heat pathogens accumulate in the Blood level of the Lower Jiao, causing dysuria without thirst, this aligns with the principle in the *Su Wen* (Chapter on Basic Questions): "Without Yin, Yang has no basis to generate; without Yang, Yin has no basis to transform." The Bladder is referred to as the "Official of the Metropolis," the organ storing body fluids. When fire lodges in water, Yang Qi fails to ascend. In such cases, the bitter-cold nature of Phellodendri Cortex (Huangbai, 黄柏) should be used to suppress fire and thereby raise Yang, allowing Yin and Yang to mutually generate. Thus, there are two types of fire: Jun Fire (Monarch Fire), which is Human Fire, specifically Heart Fire. It can be subdued by dampness, extinguished by water, or directly折 (broken/clamped down). Therefore, herbs like Anemarrhenae Rhizoma (Zhimu, 知母) and Phellodendri Cortex (Huangbai, 黄柏) are considered appropriate agents for nourishing Yin and descending fire. However, Xiang Fire (Minister Fire), also known as Heavenly Fire, Dragon-Lei Fire, or Yin Fire, cannot be subdued by water or dampness. Why? Dragon-Lei Fire erupts in the fifth and sixth lunar months and hides in the ninth and tenth. This is because in winter, Yang Qi resides beneath the water and earth, and Dragon-Lei follows this warmth to stay below; in summer, Yin Qi is below, forcing Dragon-Lei to rise above. Using Phellodendri Cortex (Huangbai, 黄柏) to subdue it would be like trying to restrain the momentum of thunder and lightning during a sudden heavy rain—is this feasible? No. Only when the sun shines does the fire naturally vanish. This is clear evidence that this fire thrives with water and is extinguished by fire. Recently, individuals with deficiency consumptive diseases or those who indulge in sexual activity often use Anemarrhenae Rhizoma (Zhimu, 知母) and Phellodendri Cortex (Huangbai, 黄柏) as the chief ingredients in yin-nourishing prescriptions, taking them daily. This excessive descending action damages the Spleen and Stomach, secretly depletes True Yang, causes the essence and Qi to lose warmth, and leads to other illnesses. One should realize that the bitter-cold, slippery, and draining nature of Huangbai and Zhimu, if taken long-term, may cause harm by following the fire path upwards. How can one not be cautious? Understanding this, it is acceptable to refer to Huangbai and Zhimu as "Descending Mothers" to nourish Yin. However, to simply label them as "Nourishing Yin and Descending Fire" is highly contradictory.