《本草经》云∶药有四气寒热温凉，此兼性气而言也。又有香臭腥臊之四气，如沉檀、脑
麝之气香，阿魏、大蒜其气臭，鱼、蛤、铜钱其气腥，鸡、鸭、狐狸其气臊，此则四气而兼性气
为言也。《本经》独言寒热温凉四性，而不言香臭腥臊，恐或遗之耳。五味酸、咸、甘、苦、辛。
盖天地定位，惟五行生化万类。生物者，气也；成之者，味也。如寒气坚，故咸味可用以软；
热气软，故苦味可用以坚；风气散，故酸味可用以收；臊气收，故辛味可用以散；土为中气，
无所不和，故甘味可用以缓。此四气五味，药之纪纲，业医者须详明之，方可以为司命之寄也。
《内经》曰∶治病必明六化分治，五味、五色所生，五脏所宜，乃可以言盈虚生病之络也。
谨候气宜，无失病机，其主病何如？曰∶司岁备物，则无遗主矣。（采药岁也。）司岁物何也？
天地之专精也。曰∶司气者何如？曰∶司气主岁同，然有余不足也。（不足则物薄，有余则物精。）
非司岁物何如？曰∶散也。（非专精则散气，散物则物不纯。）故质同而异等也。气味有浓薄，
性用有静躁，治保有多少，力化有浅深。
夫药有寒热温凉之性，有酸、苦、辛、咸、甘、淡之类，各有所能，不可不通也。夫药之
气味不必同，同气之物其味俱咸，其气皆寒之类是也。凡同气之物必有诸味，同味之物必有诸气，
互相气味各有浓薄，性用不等，制方者必明其用。
凡药昆虫草木，产之有地，根叶花实，采之有时。失其地则性味少异，失其时则气汁不全。
又况新陈之不同，精粗之不等，须采而用之，斯有效也。
《神农本草经》说：药物具有寒、热、温、凉四种气，这是兼指药物的性质和气机而言的。另外还有香、臭、腥、臊这四种气味，比如沉香、檀香、冰片、麝香的气味是香的，阿魏、大蒜的气味是臭的，鱼、蛤蜊的气味是腥的，鸡、鸭、狐狸的气味是臊的，这是将四气（气味）与四性（寒热温凉）结合起来说的。《神农本草经》只提到了寒、热、温、凉四性，而没有提到香、臭、腥、臊，恐怕是有所遗漏吧。五味是指酸、咸、甘、苦、辛。
大概天地确立方位，只有五行生化出万物。化生万物的，是气；成就万物的，是味。比如寒气能使物体坚硬，所以咸味可以用来软化坚硬的物体；热气能使物体柔软，所以苦味可以用来使柔软的物体变坚实；风气具有发散的特性，所以酸味可以用来收敛；臊气具有收敛的特性，所以辛味可以用来发散；土居中央，代表中气，无所不和，所以甘味可以用来缓和急迫。这四种气和五种味，是药物的纲领，从事医学的人必须详细明了它们，才可以承担救死扶伤的重任。
《黄帝内经》说：治病必须明白六气（风、寒、暑、湿、燥、火）的变化及其分别治疗的方法，了解五味、五色所对应的脏腑以及五脏适宜的食物，才可以谈论气血盈虚导致疾病的脉络。谨慎地观察气候的适宜与否，不要错失疾病的机理，那么主治的药物效果如何呢？回答说：顺应岁运来准备药材，就不会遗漏主治的药物了。（这是指采集药材要顺应年份。）什么是顺应岁运的药材呢？是因为它们是天地精气专一凝聚而成的。问：什么是顺应主气的药材呢？回答说：顺应主气的药材与主管一年的运气相同，但有有余和不足的区别。（不足则药力薄弱，有余则药力精纯。）那非顺应岁运的药材又是怎样的呢？回答说：是散漫不聚的。（不是精气专一就会气散，气散的药材就不纯粹。）所以虽然质地相同但等级不同。气味有浓烈和浅薄之分，药性作用有静守和躁动的区别，治疗保养的需求有多有少，药效转化的深度也有深有浅。
药物具有寒、热、温、凉的性质，有酸、苦、辛、咸、甘、淡等类别，各自有其功效，不可不通晓。药物的气味不一定相同，同一种气的物品其味道都偏咸，其气都偏寒之类就是如此。凡是气相同的物品必然具备各种味道，味道相同的物品必然具备各种气，互相之间的气味各有浓薄，药性和作用不等，制定方剂的人必须明白它们的用途。
凡是药物中的昆虫和草木，产地有地域差别，根、叶、花、实，采集有时间要求。失去适宜的产地，则药性的味道会有少许差异；失去适宜的采集时间，则药的气汁就不完整。更何况新陈药材的不同，精制与粗糙的不等，必须经过仔细挑选后使用，这样才能见效。
The *Shennong Bencao Jing* (Divine Farmer's Materia Medica) states: Medicines possess four qi (vital energies): cold, hot, warm, and cool. This refers to both their nature (xing) and qi. There are also four odors: fragrant, foul, fishy, and musky. For example, Chenxiang (Aquilaria Wood), Tanxiang (Sandalwood), Bingpian (Borneol), and Shexiang (Musk) have a fragrant odor; Awai (Ferula Assa-foetida) and Dasuan (Garlic) have a foul odor; fish and clams have a fishy odor; chickens, ducks, and foxes have a musky odor. This combines the four odors with the four natures in its description. The *Benjing* mentions only the four natures of cold, hot, warm, and cool, but does not mention the four odors, which may be an omission. The five flavors are sour, salty, sweet, bitter, and pungent.
Generally, heaven and earth establish positions, and only the Five Elements (Wood, Fire, Earth, Metal, Water) generate all living things. That which generates is qi; that which completes is flavor. For instance, cold qi tends to harden, so salty flavor can be used to soften hardness; hot qi tends to soften, so bitter flavor can be used to firm up softness; wind qi tends to disperse, so sour flavor can be used to astringe; musky qi tends to gather/astringe, so pungent flavor can be used to disperse; Earth represents central qi, harmonizing all things, so sweet flavor can be used to moderate urgency. These four qi and five flavors are the guidelines of medicine. Practitioners must understand them in detail to fulfill the trust of saving lives.
The *Huangdi Neijing* (Yellow Emperor's Inner Canon) states: In treating disease, one must clearly understand the transformations of the Six Qi (Wind, Cold, Summer Heat, Dampness, Dryness, Fire) and their respective treatments, as well as the origins of the five flavors and five colors, and what is suitable for the five Zang organs. Only then can one discuss the meridians related to excess and deficiency leading to disease. Carefully observe the appropriateness of the qi, do not miss the pathogenesis of the disease, and how will the primary treatment work? It is said: Preparing materials according to the annual climate ensures no primary efficacy is missed. (This refers to harvesting herbs according to the year.) What are materials prepared according to the year? They are the concentrated essence of heaven and earth. What about those corresponding to the ruling qi? They correspond to the ruling qi of the year, but vary in abundance or deficiency. (Deficiency results in weak potency; abundance results in pure potency.) What about non-year-specific materials? They are scattered. (Without concentrated essence, the qi scatters; scattered materials lack purity.) Thus, although the substance may be similar, their grades differ. Flavors and qi vary in intensity; properties and actions vary in stillness or agitation; indications for treatment and preservation vary in quantity; and the depth of therapeutic transformation varies.
Medicines possess natures of cold, hot, warm, and cool, and categories such as sour, bitter, pungent, salty, sweet, and bland, each having specific functions that must be understood. The qi and flavor of medicines need not be identical; for example, items with the same qi may all have a salty flavor and cold nature. Generally, items with the same qi must contain various flavors, and items with the same flavor must contain various qi. Their mutual qi and flavor vary in density, and their properties and actions are unequal. Formulators must clearly understand their applications.
All medicinal insects and plants have specific places of origin. Roots, leaves, flowers, and fruits must be harvested at specific times. If the place is incorrect, the nature and flavor will differ slightly; if the time is incorrect, the qi and juice will be incomplete. Furthermore, there are differences between new and old materials, and between refined and coarse qualities. One must select and use them properly to achieve efficacy.