王叔和曰∶妇人年五十所，一朝而清血，二三日不止，何以治之？师曰∶此妇人前绝生，经水不止，今反
清血，此为居经，不须治，当自止。经水下常五日者，五日愈。
王叔和曰∶脉微，血气俱虚，年少者，亡血也。乳子下利为可，否者此为居经，三月一来。师曰∶寸口脉
微而涩，微则卫气不足，涩则血气无余。卫不足，其息短，其形躁。血不足，其形逆，荣卫俱虚，语言谬戾。
趺阳脉浮而涩，涩则胃气虚，虚则短气，咽燥而口苦。胃气涩则失液。少阴脉微而迟，微则无精，迟则阴中寒，
涩则血不来，此为居经，三月一来。
李时珍曰∶女子，阴类也，以血为主。其血上应太阴，下应海潮。月有盈亏，潮有朝夕，月事一行，与之
相符，故谓之月水、月信、月经。经者，常也。天癸者，天一生水也。邪术家谓之红铅，谬名也。女人
之经，一月一行，其常也。或先或后，或通或塞，其病也。有行期只吐血衄血，或眼耳出血，是谓倒经逆行。
有三月一行者，是谓居经。有一年一行，是谓避年。有一生不行而受胎者，是谓暗经。有受胎之后，月月行经
而产子者，是谓胎盛，俗名垢胎。有受胎数月，血忽大下，而胎不陨者，是谓漏胎。此虽以气血有余不足言，
而亦异常矣。
慎斋按∶以上三条，序妇人经行不一也。妇人经水，一月一行，其常也。而外则有居经、有避年、有倒经、
有暗经、有垢胎、有漏胎之证，凡此皆经候不调之故也。
Wang Shuhe said: For a woman around fifty years of age, if she suddenly experiences the discharge of clear blood that does not stop for two or three days, how should it be treated? The Master said: This woman previously ceased childbearing (lost fertility), and her menses had stopped; now, conversely, she discharges clear blood. This is termed "Ju Jing" (Residential Menses) and requires no treatment; it will cease spontaneously. If the menstrual flow typically lasts five days, it will heal after five days.
Wang Shuhe said: A faint pulse indicates deficiency of both Qi and Blood. In a young woman, this is due to loss of blood. Diarrhea during lactation is acceptable; otherwise, this constitutes "Ju Jing," where menstruation occurs once every three months. The Master said: A Cun Kou (Inch position at radial artery) pulse that is faint and choppy indicates that a faint quality signifies insufficiency of Wei Qi (Defensive Qi), while a choppy quality indicates exhaustion of Blood and Qi. Insufficiency of Wei Qi leads to shortness of breath and restlessness of the body. Deficiency of Blood leads to physical disharmony; when Ying Qi (Nutritive Qi) and Wei Qi are both deficient, speech becomes erratic and incorrect. The Zu Yang (Foot-Yangming) pulse is floating and choppy; a choppy quality indicates deficiency of Stomach Qi, which causes shortness of breath, dry throat, and bitter taste in the mouth. Stagnant Stomach Qi results in loss of fluids. The Shao Yin (Lesser-Yin) pulse is faint and slow; a faint quality indicates lack of Essence, a slow quality indicates cold in the Yin region, and a choppy quality indicates absence of blood flow. This is "Ju Jing," occurring once every three months.
Li Shizhen said: Women belong to the Yin category and are primarily governed by Blood. Their blood corresponds upward to Tai Yin (Great Yin) and downward to the ocean tides. The moon has waxing and waning phases; tides have morning and evening fluctuations. Menstruation occurs monthly, corresponding with these phenomena, hence it is called Yue Shui (Monthly Water), Yue Xin (Monthly Trust), or Jing Yue (Menstrual Moon). "Jing" means constant or regular. Tian Gui (Heavenly Purity) refers to the principle of Heaven generating One Water. Esoteric practitioners erroneously call it "Red Lead." For women, menstruation occurring once a month is normal. Occurring early or late, flowing freely or obstructed, constitutes pathology. Some experience hematemesis, epistaxis, or bleeding from eyes and ears during their period; this is termed Dao Jing (Reverse Menstruation) or Ni Xing (Abnormal Flow). Some menstruate once every three months; this is Ju Jing. Some menstruate once a year; this is Bi Nian (Avoiding Year). Some never menstruate yet conceive; this is An Jing (Hidden Menstruation). Some menstruate monthly even after conception and give birth; this is Tai Sheng (Fetal Abundance), commonly known as Gou Tai (Dirt Pregnancy). Some suffer sudden heavy bleeding several months into pregnancy without miscarriage; this is Lou Tai (Leaking Fetus). Although these can be explained by excess or deficiency of Qi and Blood, they are considered abnormal conditions.
Shen Zhai commented: The above three passages describe the irregularity of menstrual cycles in women. Menstruation occurring once a month is the norm. However, external manifestations include Ju Jing, Bi Nian, Dao Jing, An Jing, Gou Tai, and Lou Tai syndromes. All these are caused by irregularities in menstrual timing.