水蛭，味咸、苦，气平、微寒，有毒。炒黄黑色用之。善祛积瘀坚瘕。仲景夫子用之为
抵当
汤丸，治伤寒之瘀血发黄也。治折伤，利水道，通月信，堕妊娠，亦必用之药。蓄血不化，
舍此安除乎。
或问蓄血之症，何故必用水蛭？盖血蓄之症，与气结之症不同，虽同是热症，而气结则
热结
于膀胱，血蓄则热结于肠胃。气结之病，可用气药散之于无形。血蓄之症，非用血物不能散
之于有形也。水蛭正有形之物，以
散其有形之血耳。何必过惧哉。（〔批〕血蓄症，非水蛭、虻虫不能消。）
或问水蛭即水田内之蚂蝗，食人血，最可恶之物也。仲景夫子偏用之治伤寒瘀血，不识
有何
药可以代之乎？曰∶血瘀蓄而不散，舍水蛭实无他药之可代。水蛭不可得，必多用虻虫代之
。然而虻虫终不及水蛭之神。今世畏之而不敢用，谁知此物并不害人耶。
或问水蛭至难死，又善变化，能一身而化为千万，宜世人疑而不敢用也，先生谓并不害
人，
此则难信也。曰∶水蛭制之不得法，则难死而能生；制之得法，则不生而永死。取水蛭之干
者，用铁刀细切如小米大，文火炒至黄黑色，有烟起取出，不可放在地上，不得土气，又安
能重生而变化哉。（〔批〕制水蛭总不可令其得土气为佳，然炒熟无生气，又安能再生哉。）
故用之同瘀血一团，从大便中尽出，得其效最捷，何至有害乎。
或问炒制水蛭，万一不得法，其性犹存，则一留肠腹之中，安得而不害人乎？曰∶何畏
之极
也。予有解之之法，用水蛭之汤，加入黄土二钱同服，即水蛭不死，断亦无害。（〔批〕又
法
之巧也。）盖水蛭以土为母，离土则无以为养。与土同用，既善于解瘀血之结，即随土而共
行，永无留滞腹肠之虞矣。
水蛭，味道咸、苦，气性平、微寒，有毒。需炒至黄黑色后使用。善于祛除体内积滞的瘀血及坚硬的癥瘕肿块。张仲景先生将其用于抵当汤和抵当丸中，治疗伤寒病导致的瘀血发黄证。治疗跌打损伤，通利水道，疏通月经，堕胎引产，也是必须使用的药物。对于蓄血证无法化解的情况，除了此药还能用什么来清除呢？
有人问：蓄血证为何一定要用水蛭？大概是因为血蓄积的病症，与气结的病症不同，虽然同属热证，但气结则是热邪结聚在膀胱，血蓄则是热邪结聚在肠胃。气结的病，可以用理气药在无形之中消散它。血蓄的症，不用血类药材就不能在形质上消散它。水蛭正是有形之物，用来消散其有形的瘀血罢了。何必过分恐惧呢。（〔批注〕血蓄证，非水蛭、虻虫不能消除。）
有人问：水蛭就是水田里的蚂蝗，吸食人血，是最令人厌恶的东西。张仲景先生偏偏用它来治疗伤寒瘀血，不知道有什么药可以替代它吗？回答说：血液瘀滞蓄积而不散开，除了水蛭实在没有别的药可以替代。如果得不到水蛭，必须多用虻虫来替代。然而虻虫终究不如水蛭神效。当今世人畏惧它而不敢使用，谁知道这东西并不害人呢。
有人问：水蛭极难杀死，又善于变化，能由一个身体化为千万个，世人怀疑而不敢使用是应该的，先生却说它并不害人，这则难以相信。回答说：水蛭如果炮制方法不得当，就难死而能活；炮制方法得当，就不生而永远死亡。取干燥的水蛭，用铁刀切成如小米大小的细片，用文火炒至黄黑色，有烟升起时取出，不可放在地上，不沾染地气，又怎么能重生并变化呢。（〔批注〕炮制水蛭总以不让其沾染地气为佳，然而炒熟后没有了生气，又怎么能再生呢。）所以将它与瘀血一团，从大便中完全排出，获得疗效最迅速，怎么会到有害的地步呢。
有人问：炒制水蛭，万一方法不得当，它的药性仍然存在，那么一旦留在肠腹之中，怎么能不害人呢？回答说：何必恐惧到极点呢。我有解除的方法，用水蛭煎煮的汤剂，加入二钱黄土一同服用，即使水蛭不死，也绝对没有危害。（〔批注〕又是巧妙的方法。）因为水蛭以土为母，离开土就没有赖以生存的营养。与水蛭同用，既然善于化解瘀血的结聚，就会随着土一起运行，永远没有滞留腹肠的忧虑了。
Leech (Shuizhi), with a salty and bitter taste, and a neutral to slightly cold nature, is toxic. It should be used after being stir-fried until yellowish-black. It excels at dispelling accumulated blood stasis and hard masses (Zhijia). Master Zhang Zhongjing employed it in Didang Tang (Cistanche Pill) and Didang Wan (Pill) to treat jaundice caused by blood stasis in Cold Damage diseases. It is also an essential herb for treating traumatic injuries, promoting urination, regulating menstruation, and inducing abortion. When blood accumulation fails to resolve, what other means could remove it but this herb?
A question arises: Why must leech be used for blood accumulation syndromes? The reason is that blood accumulation differs from qi stagnation. Although both are heat syndromes, qi stagnation involves heat binding in the Bladder, whereas blood accumulation involves heat binding in the Intestines and Stomach. Diseases of qi stagnation can be dispersed by qi-regulating herbs into formlessness. However, blood accumulation cannot be dispersed into formlessness without using blood-invigorating substances. Leech is precisely such a tangible substance, used to dissipate tangible blood stasis. Why fear it excessively? (Commentary: Blood accumulation syndromes cannot be eliminated without leech or horsefly.)
Another question: Leech is the leech found in rice paddies, which feeds on human blood and is the most detestable creature. Why did Master Zhang Zhongjing specifically use it to treat blood stasis in Cold Damage? Is there any herb that can substitute for it? The answer is: When blood is stagnant and accumulated without dispersing, there is truly no other herb to replace leech. If leech is unavailable, one must use a larger dose of horsefly (Mengchong) as a substitute. However, horsefly ultimately falls short of the efficacy of leech. People today fear it and dare not use it; who knows that this creature does not harm humans?
Yet another question: Leech is extremely difficult to kill and possesses great transformative abilities, seemingly able to multiply from one body into thousands. It is understandable that people doubt and dare not use it. Yet you claim it does not harm humans, which is hard to believe. The response is: If leech is processed improperly, it may survive and remain alive; if processed correctly, it will die permanently and lose its vitality. Take dried leech, slice it finely with an iron knife into pieces the size of millet grains, and stir-fry over gentle heat until yellowish-black. Remove when smoke rises. Do not place it on the ground to avoid absorbing earth qi; otherwise, how could it regenerate and transform? (Commentary: In processing leech, it is best to prevent contact with earth qi. Once stir-fried thoroughly, it loses its vital energy and cannot regenerate.) Thus, when administered together with blood stasis, it is completely expelled through the bowels, yielding the fastest therapeutic effect. How could it possibly cause harm?
Someone asks: If the stir-frying process of leech is improper and its properties remain active, leaving it in the intestines and abdomen would surely be harmful. The reply is: Why fear so excessively? I have a method to counteract this. By adding two qian of loess (Huangtu) to the decoction of leech and taking them together, even if the leech survives, it will certainly cause no harm. (Commentary: Another ingenious method.) Since leech regards earth as its mother, it cannot sustain itself without earth. Used together with earth, while effectively resolving blood stasis, it moves along with the earth and eliminates any concern about lingering in the abdominal intestines.