药物众多，各一其性，宜否万殊，难以尽识。用者不得其要，未免多误。兼之《本草》
所注，又皆概言其能，凡有一长，自难泯没。惟是孰为专主，孰为兼能，孰为利于此而不利
于彼，孰者宜于补而不宜于攻。学人昧其真性，而惟按图以索骥，所以用多不效，益见用药
之难矣。用药之道无他也，惟在精其气味，识其阴阳，则药味虽多，可得其要矣。凡气味之
辨，则诸气属阳，诸味属阴。气本乎天，气有四，曰寒热温凉是也。味本乎地，味有六，曰
酸苦甘辛咸淡是也。温热者，天之阳；寒凉者，天之阴也。辛甘淡者，地之阳；酸苦咸者，
地之阴也。阳主升而浮，阴主沉而降。辛主散，其行也横，故能解表。甘主缓，其行也上，
故能补中。苦主泻，其行也下，故可去实。酸主收，其性也敛，故可治泄。淡主渗，其性也
利，故可厘清。咸主软，其性也沉，故可导滞。用纯气者，用其动而能行；用纯味者，用其
静而能守。有气味兼用者，和合之妙，贵乎相成。有君臣相配者，宜否之机，最嫌相左。既
曰合宜，尤当知忌，先避其害，后用其利，一味不投，众善俱弃。故欲表散者，须远酸寒；
欲降下者，勿兼升散。阳旺者，当知忌温；阳衰者，沉寒毋犯。上实者忌升，下实者忌秘。
上虚者忌降，下虚者忌泄。诸动者再动即散，诸静者再静即灭。甘勿施于中满，苦勿施于假
热，辛勿施于热躁，咸勿施于伤血。酸木最能克土，脾气虚者少设。阳中还有阴象，阴中复
有阳诀，使能烛此阴阳，则药理虽玄，岂难透彻。
五味所入，《内经》曰∶五味入胃，各归所喜，故酸先入肝，苦先入心，甘先入脾，辛
先入肺，咸先入肾。久而增气，物化之常也。气增而久，夭之由也。
药物种类繁多，每种药物都有其独特的药性，适宜与不适宜的情况千差万别，很难全部认识清楚。使用药物的人如果不得要领，难免会出现很多错误。加上《本草》中所记载的内容，大多概括地说明药物的功效，凡是有一技之长的药物，自然难以被埋没。只是其中哪些是主要功效，哪些是兼有功效，哪些对此病有利而对彼病不利，哪些适宜于补益而不适宜于攻伐。学习者如果不明白药物的真实性质，只是按照图谱来寻找良方，所以用药往往不见疗效，更加显示出用药的困难了。用药的道理没有别的，只在于精通药物的气味，识别药物的阴阳属性，那么虽然药味繁多，也能掌握其关键了。大凡对气味的辨别，所有气属于阳，所有味属于阴。气源于天，气有四种，即寒、热、温、凉。味源于地，味有六种，即酸、苦、甘、辛、咸、淡。温热属于天之阳；寒凉属于天之阴。辛、甘、淡属于地之阳；酸、苦、咸属于地之阴。阳主升浮，阴主沉降。辛味主发散，其作用趋向横向，所以能解除表邪。甘味主缓和，其作用趋向向上，所以能补益中焦。苦味主泻下，其作用趋向向下，所以可以去除实邪。酸味主收敛，其性质收敛，所以可以治疗泄泻。淡味主渗利，其性质通利，所以可以分清去浊。咸味主软坚，其性质沉降，所以可以疏导积滞。单独使用纯气药物的，是利用其动而能运行的特性；单独使用纯味药物的，是利用其静而能守的特性。有气味兼用的药物，配合的妙处，贵在相互成就。有君臣配伍的药物，适宜与否的关键，最忌讳相互抵触。既然说配合适宜，更应当知道禁忌，先避开其危害，后利用其益处，一味药不合宜，所有的良效都会抛弃。所以想要解表发散的，必须远离酸寒之品；想要降逆下行的，不要兼用升散之品。阳气旺盛者，应当知道忌用温燥；阳气衰弱者，严禁触犯沉寒之品。上部实证忌用升提，下部实证忌用秘涩。上部虚证忌用降泄，下部虚证忌用攻下。凡是动性的药物，再用动性就会耗散；凡是静性的药物，再用静性就会熄灭。甘味药不要施用于中焦痞满的患者，苦味药不要施用于假热的患者，辛味药不要施用于热躁的患者，咸味药不要施用于伤血的患者。酸味属木，最能克制脾土，脾气虚弱者应少用或不用。阳中还有阴象，阴中也有阳诀，如果能洞察这些阴阳关系，那么药理虽然玄妙，难道难以透彻理解吗？
关于五味所入，《内经》说：五味进入胃中，各自归于其所喜应的脏腑，所以酸味先入肝，苦味先入心，甘味先入脾，辛味先入肺，咸味先入肾。长期食用某种味道会增加相应脏腑的气，这是事物变化的常态。但是气增加久了，就是折寿的原因。
There are numerous medicinal substances, each possessing its unique nature. Their suitability varies greatly, making it difficult to fully comprehend them. If practitioners fail to grasp the essentials, errors are inevitable. Furthermore, the annotations in *Bencao* (Compendium of Materia Medica) generally describe their capabilities; any substance with a particular strength is unlikely to be overlooked. However, determining which effects are primary and which are secondary, which are beneficial for one condition but detrimental for another, and which are suitable for tonification but not for purging, remains challenging. Learners who lack an understanding of the true nature of herbs and merely rely on diagrams to find remedies often find treatments ineffective, further highlighting the difficulty of prescribing. The principle of using medicines lies not in complexity, but in mastering their flavors and aromas and recognizing their Yin-Yang attributes. By doing so, even with a vast array of substances, one can grasp the key points.
Regarding the distinction between flavors and aromas: all aromas belong to Yang, and all flavors belong to Yin. Aromas originate from Heaven and have four types: Cold, Hot, Warm, and Cool. Flavors originate from Earth and have six types: Sour, Bitter, Sweet, Pungent, Salty, and Bland. Warm and Hot correspond to the Yang of Heaven; Cold and Cool correspond to the Yin of Heaven. Pungent, Sweet, and Bland correspond to the Yang of Earth; Sour, Bitter, and Salty correspond to the Yin of Earth. Yang governs ascending and floating movements, while Yin governs sinking and descending movements. Pungent flavor governs dispersion; its action moves horizontally, thus resolving the exterior. Sweet flavor governs moderation; its action moves upward, thus tonifying the Middle Jiao. Bitter flavor governs purging; its action moves downward, thus eliminating excess pathogens. Sour flavor governs astringency; its nature is contracting, thus treating diarrhea. Bland flavor governs permeation; its nature is promoting urination, thus separating clear from turbid. Salty flavor governs softening hardness; its nature is sinking, thus guiding stagnation. When using pure aromatic substances, one utilizes their dynamic ability to circulate; when using pure flavorful substances, one utilizes their static ability to retain. When both aroma and flavor are present, the subtlety of combination lies in mutual reinforcement. In the pairing of Sovereign and Minister herbs, the key to appropriateness lies in avoiding contradiction. Even when combinations are appropriate, contraindications must be known: first avoid harm, then utilize benefits. If one herb is unsuitable, all potential benefits are lost. Therefore, when aiming to disperse the exterior, one must avoid Sour and Cold substances; when aiming to descend, one must not combine with Ascending and Dispersing substances. For those with excessive Yang, Warm substances should be avoided; for those with deficient Yang, Sinking-Cold substances must not be touched. Upper Excess conditions contraindicate Ascending therapies; Lower Excess conditions contraindicate Constipating therapies. Upper Deficiency conditions contraindicate Descending therapies; Lower Deficiency conditions contraindicate Purging therapies. Substances with dynamic properties, if used excessively, will dissipate; substances with static properties, if used excessively, will extinguish. Sweet substances should not be administered to patients with Middle Jiao fullness; Bitter substances should not be administered to patients with false heat; Pungent substances should not be administered to patients with heat and restlessness; Salty substances should not be administered to patients with blood injury. Sour, associated with Wood, can most effectively overcome Earth (Spleen); therefore, it should be used sparingly in cases of Spleen Qi deficiency. Within Yang, there are Yin manifestations; within Yin, there are Yang principles. If one can illuminate these Yin-Yang relationships, although the pharmacology may seem profound, it is certainly not difficult to penetrate.
Regarding the entry of the Five Flavors, the *Neijing* (Inner Canon) states: "The five flavors enter the stomach and each returns to its preferred organ. Thus, Sour enters the Liver first, Bitter enters the Heart first, Sweet enters the Spleen first, Pungent enters the Lung first, and Salty enters the Kidney first." Long-term consumption increases the Qi of the corresponding organ, which is the normal law of transformation. However, if this increase persists for too long, it becomes the cause of premature death.