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Shuizhi (Leech, Hirudo nipponia): It has a salty taste, black color, putrid odor, and neutral nature. Due to its salty taste, it is adept at entering the Blood aspect; because it is originally a creature that sucks blood, it is adept at breaking up Blood stasis; due to its putrid odor, its scent resonates with Blood stasis but not with fresh Blood, thus it breaks up only Blood stasis without damaging new Blood. Furthermore, its black color directs downwards, making it effective in breaking up stasis within the Chong and Ren vessels. Its ability to break up Blood stasis is an inherent capability of this creature, not due to a fierce nature. The *Shennong Bencao Jing* states it treats female infertility, as infertility often stems from stasis in the Chong and Ren vessels; once the stasis is removed, conception becomes possible. Specifically, its salty taste corresponds to the flavor of Water, its black color to the color of Water, and its putrid odor to the Qi of Water. It is purely generated from the essence of Water, so it is most suitable for raw use and strongly contraindicated for fire-roasting.

Generally, drugs that break up Blood stasis tend to damage the Qi aspect, whereas Shuizhi (Leech), being salty and specifically entering the Blood aspect, causes no harm to the Qi. Moreover, after ingestion, there is no abdominal pain nor sensation of rupture, yet the Blood stasis silently dissipates invisibly; truly a good medicine. In my treatment of women with Amenorrhea (absence of menstruation) and Jia Masses (abdominal masses), if the pulse is not weak, I often use only Shuizhi (Leech) ground into fine powder, taken with boiled water, one qian per dose, twice daily. Even firm stasis accumulated over years can be completely eliminated within one month.

Both Shuizhi (Leech) and Mengchong (Horsefly) are agents for breaking up Blood stasis. However, in my experiments using them separately, Mengchong was ineffective while Shuizhi was effective. By general reasoning, any creature that feeds on blood can break up blood. Yet, Mengchong feeds on blood with its proboscis, whereas Shuizhi feeds with its body. When its body adheres tightly to another object, it can suck the blood from that object, hence its efficacy in breaking up Blood stasis is superior. Modern formularies often claim that Shuizhi must be thoroughly roasted before use; otherwise, it will reproduce inside the human abdomen and harm the patient. This is indeed nonsense. I once treated a woman whose menstruation was regular but who failed to conceive. Upon detailed inquiry, a Jia Mass was found in the lower abdomen. I prescribed solely one liang of Shuizhi, roasted thoroughly in sesame oil, and powdered. Each dose was five fen, taken twice daily. After finishing the course, there was no effect. Subsequently, I switched to raw Shuizhi, administered as before. Before the full liang was consumed, the mass had completely dissipated, and she gave birth to a son the following year. However, for those with Qi and Blood deficiency, it is advisable to supplement with herbs that tonify Qi and Blood.

One might ask: Why is there such a drastic difference in efficacy between roasted and raw Shuizhi? The answer is: This creature lives in water, possesses the color black (color of Water), taste salty (flavor of Water), and odor putrid (Qi of Water), having been born from the essence of Water. Roasting damages this essence of Water, rendering it ineffective. This characteristic applies generally to aquatic substances such as Longgu (Fossilized Bones), Muli (Oyster Shell), and Guiban (Turtle Shell). Therefore, Wang Hongxu in *Waike Zhengzhi Quansheng Ji* stated that when using Longgu, it should be suspended in a well overnight before use, indicating its aversion to fire, which is even more pronounced with Shuizhi. However, grinding raw Shuizhi into powder is difficult. If not ground finely enough, it can be sun-dried and re-ground, or placed in paper packets on the stove top to dry. This requires personal supervision; if entrusted to a pharmacy, by the time it needs further grinding, it would inevitably be baked with fire. Westerners treat heat-induced swelling and pain by placing several live leeches on the affected area, covering them with a glass cup to suck out toxic blood, which is also a good method.