气温，味甘酸咸，属土而有水与火。峻补精血，骤用反致动大便，脾泄者不宜用。酒洗
用之。阳事不举，必须用之，不可缺也。
用药之难，非顺用之难，逆用之难也。非逆用之难，逆用而与病情切合之难也。医者知
以寒治热，以热治寒，以通治塞，以塞治通，热者热之无遗，寒者寒之无遗而已矣。然内经
有塞因塞用，通因通用，寒因热用，热因寒用，用热远热，用寒远寒，则又何以说也？盖塞
因塞用者，若脾虚作胀，治以参术，脾得补而胀自消也；通因通用者，若时感挟热下痢，或
中有燥屎，用调胃承气汤下之乃安，通之而愈也；寒因热用者，药本寒也，而反佐之以热；
热因寒用者，药本热，而反佐以寒，俾无格拒之患，所谓必先其所主，而伏其所因也；用热
远热，用寒远寒者，如寒病宜投热药，热病宜投寒药，仅使中病而已，勿过用焉，过用则反
为药伤矣。故曰∶病无常形，医无常方，药无常品，在人之善学善用耳。
余家藏有明代皖医杜文燮所编《药鉴》一书，喜其能纂集昔人用药要言，参以一己经验，
便诵习，资启发，遂志数语，以公诸世。
张耀卿一九七三年八月上海
肉苁蓉药性温和，味甘、酸、咸，五行属性属土，但兼具水与火的特性。它能峻补精血，但若突然大量使用，反而会导致大便滑泄，脾虚泄泻者不宜使用。需用酒清洗后入药。对于阳痿不举之症，必须使用此药，不可或缺。
用药的难点，不在于顺证时使用药物的难度，而在于逆证时使用药物的难度；而逆证用药的难点，又在于逆用之法能与病情相契合的难度。医生只知道以寒治热、以热治寒、以通治塞、以塞治通，对热证彻底使用寒药，对寒证彻底使用热药罢了。然而《黄帝内经》中提出了“塞因塞用”、“通因通用”、“寒因热用”、“热因寒用”，以及“用热远热”、“用寒远寒”等原则，这又该如何解释呢？所谓“塞因塞用”，例如脾虚导致的腹胀，用人参、白术治疗，脾气得到补益，腹胀自然消除；所谓“通因通用”，例如外感时邪兼有内热导致的下痢，或者体内有燥屎积结，使用调胃承气汤（Tiaowei Chengqi Decoction）攻下后才能安宁，通过通下的方法使疾病痊愈；所谓“寒因热用”，是指药物本性为寒，却反佐以热性药；所谓“热因寒用”，是指药物本性为热，却反佐以寒性药，以此避免格拒（机体对药物产生排斥反应）的祸患，这就是所说的必须先抓住疾病的主因，从而伏制其病因；所谓“用热远热，用寒远寒”，例如寒病适宜投用热药，热病适宜投用寒药，只要达到治愈疾病的目的即可，不要过度使用，过度使用反而会遭受药物的伤害。所以说：疾病没有固定的形态，医生没有固定的处方，药物没有固定的功效，关键在于人是否善于学习和善于运用。
我家收藏有明代安徽医家杜文燮所编纂的《药鉴》一书，喜欢它能够汇集前人用药的要言精论，并参杂个人的临床经验，便于诵读学习，启发智慧，于是写下几句志语，将其公之于世。
张耀卿 一九七三年八月 上海
Cistanche Herba (Roucongrong) has a mild temperature and a sweet, sour, and salty taste. Its elemental nature belongs to Earth, yet it incorporates the characteristics of Water and Fire. It vigorously tonifies essence and blood; however, sudden or heavy use may instead induce loose stools, making it unsuitable for patients with Spleen deficiency diarrhea. It should be used after being washed with wine. For impotence (Yang shi bu ju), this herb is indispensable and must not be omitted.
The difficulty in prescribing medication lies not in treating straightforward cases (Shun yong), but in treating complex or paradoxical cases (Ni yong); and the difficulty in treating paradoxical cases lies not merely in using them oppositely, but in ensuring that such opposite application aligns precisely with the patient's condition. Physicians typically know only to treat heat with cold, cold with heat, obstruction with unblocking, and unblocking with obstructing—applying cold remedies thoroughly to heat patterns and hot remedies thoroughly to cold patterns. However, the *Huangdi Neijing* (Yellow Emperor's Inner Canon) proposes principles such as "treating obstruction with obstruction" (Sai yin sai yong), "treating discharge with discharge" (Tong yin tong yong), "treating cold with heat" (Han yin re yong), "treating heat with cold" (Re yin han yong), and "avoiding heat when using hot medicines, avoiding cold when using cold medicines" (Yong re yuan re, yong han yuan han). How are these to be explained? "Treating obstruction with obstruction" refers to cases like abdominal distension caused by Spleen deficiency, which is treated with Ginseng Radix et Rhizoma (Renshen) and Atractylodis Macrocephalae Rhizoma (Baizhu); once the Spleen Qi is tonified, the distension naturally resolves. "Treating discharge with discharge" refers to dysentery accompanied by internal heat due to seasonal pathogens, or constipation due to dry feces retained in the intestines; treatment involves administering Tiaowei Chengqi Decoction (Stomach-Regulating Orderly Flow Decoction) to purge the bowels, thereby achieving cure through unblocking. "Treating cold with heat" means that although the primary drug is cold in nature, it is counter-assisted (Fan zuo) by hot herbs. "Treating heat with cold" means that although the primary drug is hot in nature, it is counter-assisted by cold herbs, thereby preventing rejection (Ge ju) reactions where the body expels the medicine. This is what is meant by: one must first address the primary cause and subdue the underlying etiology. "Avoiding heat when using hot medicines, avoiding cold when using cold medicines" implies that while cold diseases should be treated with hot medicines and heat diseases with cold medicines, one should aim only for therapeutic efficacy without overuse; excessive use will lead to injury caused by the medicine itself. Therefore, it is said: Diseases have no fixed form, physicians have no fixed prescriptions, and medicines have no fixed properties; success depends entirely on the practitioner's ability to learn and apply wisely.
My family possesses a copy of the book *Yao Jian* (Mirror of Medicines), compiled by Du Wenxie, a physician from Anhui during the Ming Dynasty. I appreciate its compilation of essential statements on herbal usage from past masters, integrated with personal clinical experience, making it convenient for study and inspiring for enlightenment. Thus, I have written these few words to share it with the world.
Zhang Yaoqing, August 1973, Shanghai