半夏∶味辛，性温，有毒。凡味辛之至者，皆禀秋金收降之性，故力能下达为降胃安冲之主药。为其能降
胃安冲，所以能止呕吐，能引肺中、胃中湿痰下行，纳气定喘。能治胃气厥逆、吐血、衄血（《内经》谓阳明
厥逆衄呕血，阳明厥逆，即胃气厥逆也）。惟药局因其有毒，皆用白矾水煮之，相制太过，毫无辛味，转多矾
味，令人呕吐，即药局所鬻之清半夏中亦有矾，以之利湿痰犹可，若以止呕吐及吐血、衄血，殊为非宜。愚治
此等证，必用微温之水淘洗数次，然后用之，然屡次淘之则力减，故须将分量加重也。
愚因药局半夏制皆失宜，每于仲春季秋之时，用生半夏数斤，浸以热汤，日换一次，至旬日，将半夏剖
为两瓣，再入锅中，多添凉水煮一沸，速连汤取出，盛盆中，候水凉，净晒干备用。每用一两，煎汤两茶盅，
调入净蜂蜜二两，徐徐咽之。无论呕吐如何之剧，未有不止者。盖古人用半夏，原汤泡七次即用，初未有用白
矾制之者也。
【附案】邻村王姓童子，年十二三岁，忽晨起半身不能动转，其家贫无钱购药，赠以自制半夏，俾为末
每服钱半，用生姜煎汤送下，日两次，约服二十余日，其病竟愈。盖以自制半夏辛味犹存，不但能利痰，实有
开风寒湿痹之力也。
东洋××××日，英国军医×××屡屡吐，绝食者久矣。其
弟与美医××氏协力治疗之，呕吐卒不止，乞诊于余，当时已认患者为不起之人，但求余一决其死生而已。美
医××氏等遂将患者之证状及治疗之经过，一一告余。余遂向两氏曰∶余有一策，试姑行之。遂辞归检查汉法
医书，制小半夏加茯苓汤，贮瓶令其服用，一二服后奇效忽显，数日竟回撤消有之康健。至今半夏浸剂，遂为
一种之镇呕剂，先行于医科大学，次及于各病院与医家。
按∶此证若用大半夏汤加赭石尤效，因吐久则伤津伤气，方中人参能生津补气，加赭石以助之，力又专于
下行也。若有热者，可再加天冬佐之，若无自制半夏，可用药局清半夏两许，淘净矾味入煎。
半夏：味道辛，性质温，有毒。凡是味道极其辛的药材，都禀受了秋季金气收敛下降的特性，因此力量能够向下运行，是降胃气、平冲逆的主要药物。因为它能降胃气、平冲逆，所以能止住呕吐，能引导肺中、胃中的湿痰下行，收纳肺气、平息喘息。能治疗胃气厥逆、吐血、鼻出血（《内经》说阳明经气厥逆会导致鼻出血和呕吐血，阳明经气厥逆，就是胃气厥逆）。只是药店因为半夏有毒，都用白矾水煮它，相互制约太过，完全没有了辛味，反而多了白矾的味道，让人呕吐，即使是药店出售的清半夏中也含有白矾，用它来利湿痰还可以，如果用来止呕吐以及吐血、鼻出血，非常不适宜。我治疗这些病症，一定用微温的水淘洗数次，然后使用，但是多次淘洗则药力减弱，所以必须增加剂量。
我因为药局的半夏炮制都不合适，经常在仲春或仲秋时节，用生半夏几斤，浸泡在热水中，每天换一次水，到十天时，将半夏剖开成两瓣，再放入锅中，多加凉水煮沸一次，迅速连汤取出，盛在盆中，等水凉后，洗净晒干备用。每次用一两，煎汤两茶盅，调入干净的蜂蜜二两，慢慢咽下。无论呕吐多么剧烈，没有不止住的。大概古人使用半夏，原本是用汤泡七次就使用，起初并没有用白矾炮制的。
【附案】邻村王姓童子，年龄十二三岁，忽然早晨起床半身不能动弹，他家贫穷没钱买药，赠送给他自制的半夏，让他研成粉末，每次服用一钱半，用生姜煎汤送服，每天两次，大约服用二十多天，他的病竟然痊愈了。大概因为自制的半夏辛味还存在，不仅能利痰，实在有开通风寒湿痹阻的力量。
东洋某日，英国军医某某屡次呕吐，已经很久绝食了。他的弟弟和美国医生某某氏协力治疗他，呕吐最终不停止，请求我诊治，当时已经认定患者是不治之症，只求我判断他的死生而已。美国医生某某氏等人于是将患者的症状及治疗的经过，一一告诉我。我于是对两位医生说：我有一个策略，试着暂时施行。于是辞别回家检查汉方医书，配制小半夏加茯苓汤，装在瓶子里让他们服用，吃一两副后奇效突然显现，几天后竟然完全康复恢复健康。从此半夏浸剂，遂成为一种镇呕剂，先在医科大学流行，其次普及到各医院和医生家。
按语：这个病症如果用大半夏汤加上赭石尤其有效，因为呕吐久了会伤津液伤正气，方中的人参能生津补气，加上赭石来帮助它，力量又专门于向下运行。如果有热象，可以再加点天冬辅助它，如果没有自制半夏，可以用药店清半夏一两左右，淘洗干净白矾味道后入煎。
Pinellia Rhizome (Banxia): Flavor pungent, nature warm, toxic. All substances with an extremely pungent flavor inherit the property of autumnal Metal to converge and descend; therefore, their force is capable of moving downward, making them the principal herbs for descending stomach Qi and pacifying rebellious Qi. Because they can descend stomach Qi and pacify rebellious Qi, they are able to stop vomiting, guide damp-phlegm from the lungs and stomach downward, grasp Qi, and calm asthma. They treat rebellious Qi of the Stomach, hematemesis, and epistaxis (The *Neijing* states that rebellious Qi of the Yangming channel causes epistaxis and vomiting blood; rebellious Qi of the Yangming channel refers to rebellious Qi of the Stomach). However, pharmacies, due to its toxicity, boil it in alum water. This excessive counteraction eliminates the pungent flavor entirely, leaving mostly the taste of alum, which induces vomiting. Even the "Qing Banxia" sold by pharmacies contains alum. While it may be acceptable for draining damp-phlegm, it is highly unsuitable for stopping vomiting, hematemesis, or epistaxis. In treating such conditions, I always rinse it several times with lukewarm water before use. However, repeated rinsing reduces its potency; thus, the dosage must be increased.
Since the processing of Pinellia Rhizome in pharmacies was improper, during mid-spring or mid-autumn, I would take several jin of raw Pinellia Rhizome, soak it in hot water, changing the water once daily. After ten days, I would split the rhizomes into two halves, place them back in a pot, add ample cool water, bring to a boil once, quickly remove them along with the decoction, place them in a basin, wait for the water to cool, then wash and sun-dry them for preparation. For each usage of one liang, decoct in enough water to yield two teacups of liquid, mix in two liang of pure honey, and swallow slowly. Regardless of how severe the vomiting, it invariably stops. The ancients used Pinellia Rhizome after soaking in boiling water seven times; initially, there was no use of alum processing.
[Attached Case] A boy surnamed Wang from a neighboring village, aged twelve or thirteen, suddenly found himself unable to move his body upon waking in the morning. His family was too poor to afford medicine. I gifted him my self-prepared Pinellia Rhizome, advising him to grind it into powder. He took half a qian per dose, delivered with a decoction of fresh ginger, twice daily. After approximately twenty days, his illness was completely cured. This is because the self-prepared Pinellia Rhizome retained its pungent flavor; not only could it drain phlegm, but it also possessed the power to open blockages caused by wind-cold-dampness.
On a certain day in Japan, a British military surgeon suffered from recurrent vomiting and had been fasting for a long time. His brother and an American physician, Mr. XX, collaborated on his treatment, but the vomiting persisted. They sought my consultation. At that time, he was considered incurable, and they merely asked me to determine his prognosis. The American physician and others recounted the patient's symptoms and the course of treatment to me in detail. I said to them: "I have a strategy; let us try it tentatively." I returned home, consulted Chinese medical texts, prepared Xiao Banxia Jia Fuling Tang (Minor Pinellia Decoction plus Poria), stored it in a bottle for their administration. After one or two doses, a miraculous effect appeared, and within a few days, he made a complete recovery. Since then, Pinellia Rhizome infusions have become a type of antiemetic, first popularized in medical universities, and subsequently adopted by various hospitals and practitioners.
Note: If this condition were treated with Da Banxia Tang (Major Pinellia Decoction) added with Hematitum (Ochre), the efficacy would be even greater. Prolonged vomiting damages fluids and Qi; Ginseng Radix et Rhizoma (Renshen) in the formula generates fluids and tonifies Qi, while adding Ochre assists this action, directing the force specifically downward. If heat signs are present, Asparagus Fern Root (Tian Dong) can be added as an assistant. If self-prepared Pinellia Rhizome is unavailable, one may use about one liang of pharmacy-grade Qing Banxia, thoroughly rinsed to remove the alum taste, before decocting.