Zhīmǔ 知母
From the Běncǎo Bèiyào 本草備要 (1694).
瀉火補水，潤燥滑腸
Drains fire, tonifies water, moistens dryness and lubricates the intestines.
辛苦寒滑。
Pungent and bitter, cold and lubricating.
上清肺金而瀉火（瀉胃熱、膀胱邪熱、腎命相火），下潤腎燥而滋陰，入二經氣分（黃柏入二經血分，故二藥必相須而行）。消痰定嗽，止渴安胎（莫非清火之用）。
Ascends and clears lung-metal and drains heat (drains stomach fire, bladder evil-fire, [in addition] to kidney, mingmen and ministerial-fire). Descends to moisten kidney dryness and enriches yīn, enters the qì aspect of these two channels (huángbǎi enters the blood aspect of these two channels, therefore these two herbs are mutually reliant on each other [when used together]). Disperses phlegm and stabilises cough, allays thirst and quietens the foetus (invariably [all its] functions are clearing fire).
治傷寒煩熱，蓐勞（產勞）骨蒸（退有汗之骨蒸），燥渴虛煩，久瘧下痢（治嗽者，清肺火也，治渴者，清胃熱也。退骨蒸者，瀉腎火也），利二便，消浮腫（小便利則腫消。東垣曰：熱在上焦氣分，結秘而渴，乃肺中伏熱，不能生水，膀胱絕其化源。
[Zhīmǔ] treats cold damage (shānghán) heart vexation, childbirth taxation (taxation during delivery) steaming bone (abates the sweating of steaming bone), Dry [mouth] and thirst with vacuity vexation, enduring malaria and dysentery (Ceases cough by clearing lung fire. Ceases thirst by clearing stomach heat. Abates steaming bone by draining kidney fire). Disinhibits urination and defecation, disperses puffy swelling ([once] the urine is disinhibited then the swelling will dissipate. Dōngyuán states heat that is located in the upper jiāo qì aspect, [it will] knot and obstruct and cause thirst, this is latent heat within the lung, [the lung] cannot generate water, the bladder is severed from its source of transformation.
宜用滲濕之藥，瀉火清金，滋水之化源。熱在下焦血分，便閉而不渴，乃真水不足，膀胱乾涸，無陰則陽無以化。宜用黃柏、知母大苦寒之藥，滋腎與膀胱之陰。而陽自化，小便自通。丹溪曰：小便不通，有熱有濕，有氣結於下，宜清、宜燥、宜升。
It is appropriate to use herbs that percolate dampness, drain fire and clear metal, and enrich water at the source of transformation. Heat located in the lower jiāo blood aspect, there will be constipation and absence of thirst, this is due to insufficiency of true water (i.e. the kidneys) and dryness and desiccation of the bladder, when there is absence of yīn then yáng is unable to perform transformation. It is appropriate to use huángbǎi and zhīmǔ; herbs that are strongly bitter and cold [in order to] enrich the yīn of kidney and bladder. And then yáng will naturally transform, and urination will spontaneously flow. Dānxī states for urinary stoppage, [there are patterns] of heat, dampness, and qì knotting in the lower, [in these cases] it is appropriate to clear, dry and ascend.
又有隔二隔三之治。如肺不燥，但膀胱熱，宜瀉膀胱，此正治；如因肺熱不能生水，則清肺，此隔二之治；如因脾濕不運而精不上升，故肺不能生水，則燥胃健脾，此隔三之治。瀉膀胱，黃柏、知母之類；清肺，車前、茯苓之類；燥脾，二術之類。昂按：凡病皆有隔二隔三之治，不獨便閉也）。
Also there are treatments of two sections and three sections]. If the lung is not dry, but the bladder is hot, it is appropriate to drain the bladder, this is straight treatment. If there is lung heat and it cannot engender water, then clear the lung, these two sections [require] treatment.
If there is spleen damp and it cannot transport and then the essence does not ascend, then [also] the lung cannot engender water, then dry the stomach and fortify the spleen, these three sections [require] treatment. Drain the bladder heat with [herbs] like huángbǎi and zhīmǔ; clear the lung with [hebs] like chēqián and fúlíng; dry the spleen with [herbs] like the two types of shù (báizhú and cāngzhú). Wāng Áng states: all diseases that require treatment of two or three sections, not only constipation).
然苦寒傷胃而滑腸，多服令人瀉（李士材曰：苦寒肅殺，非長養萬物者也。世以其滋陰，施之虛損之人，則如水益深矣，特表出以為戒）。
Yet the bitter-cold [nature] damages the stomach and lubricates the intestines, it is often taken to drain (or cause diarrhoea) (Lǐ Shìcái states: bitter-cold herbs are harsh, [they] stop the ten thousand things from growing and nourishing. Later generations use it to enrich yīn, give to people with vacuity detriment, but if water is too greatly increased, tè biǎo chū yǐwéi jiè)