Among the numerous plants, animals and minerals spread around the world, there are about three thousands of them that remain in documentary forms. They have been used for several thousand years as the means of preventing and curing a variety of disease.
Materia medica is a special subject, studying origin, collection, preparation, properties and applications about oriental medical drugs, and most of them are made of plants. Therefore, it has been called, 'Bon-cho'

As early as the primitive times, while looking for food, mankind accidentally discovered that some plants could alleviate or eliminate sufferings from diseases.
Moreover, they had found which of them could have influences on physiological functions of body
; in doing so, people could even discriminate between poisonous and nonpoisonous plants.
Based on the following three factors,
(1) close observations over nature,
(2) transactions between the regions of different culture and
(3) experiences accumulated from them, the early herbal medical treatment could be formed.
This is also supported by a vivid description from the record of Shen Nong(a legendary oriental god in ancient times who was believed to govern medicine and farming) who tasted a hundred of herbs including 70 toxic substances in a single day.
With the increase in Chinese drugs, the development of their practical use and the research into theory on their properties, special books on Chinese herbs were published.
In the history of the development of Chinese books, there were five herbal classic: Shen Nong's Herbal Classic in late East Han Dynasty, Vanrum of Shen Nong's Herbal in Liang Dynasty,The Newly-Revised Materia Medica in Tang Dynasty, Classic Classified Materia Medica for Emergency in Song Dynasty, Compendium of Materia Medica in Ming Dynasty and Supplement to the Compendium of Materia Medica in Qing Dynasty. Among them,Shen Nong's Herbal Classic is the earliest Special book on Chinese materia medica,The Newly-Revised Materia Medica is the earliest pharmacopeial book, and Compendium of Materia Medica has a relatively enormous influence in the world.

Amount of active ingredients in medicinal parts of animals or plants vary from time to time during their growth , which directly influences their qualities and curative effects.
Therefore ,it is important to collect in good time when the contents of active ingredients in medicinal parts reach the peak level. The time for collecting different medicinal parts of plants can be summed up as follows:
1. Whole plants, stems and leaves are mostly collected when plants are in full bloom or in early blossom
2. Flowers are generally collected in bud or in early blossom.
3. Fruits and seeds are mostly collected when they are ripe.
4. Roots and rhizomes are mostly collected in early spring when plants have not sprouted or in late autumn when the stem and leaves start withering. 5. Bark should be collected in spring and summer when it is thick.

Drugs should be processed before using or making into various forms.

1. Aims of Preparation
(1)To enhance curative effects
(2)To reduce toxic effects
(3)To change properties of drugs and expand their uses

2. Methods for Preparation

Methods for preparation of Chinese drugs include purification, preparation with water, preparation with fire and preparation with both water and fire. Methods for preparation of Chinese drugs are closely related to their clinical usages;

(1) Stir-baking
Drugs are put into a pot over a fire ,continually stir-baked to a certain extent and taken out. According to extent of heating, drugs can be stir-baked yellow, stir-baked charred or stir-baked carbonized.
To be stir-baked yellow or stir-baked charred can moderate drugs' properties or strengthen the effect of invigorating the spleen ; and to be stir-baked carbonized can strengthen the effects of stopping bleeding and arresting diarrhea.

(2) Stir-baking with liquid
The common liquid includes wine, vinegar, honey, salt solution and ginger juice. Drugs stir-baked with liquid can alter the character of a drug, increase its efficacy, reduce toxicity, remove abnormal flavour and its side effect.

(3) Calcining
Drugs in a container are directly or indirectly calcined over a fierce fire to make them pure, crispy and easy to grind. Most of the solid and hard mineral drugs or shells are directly calcined such as dragon's bone and oyster shell.

(4) Roasting
Wrapped in wet paper or flour paste, drugs are heated until the coating becomes scorched to remove oil and irritating from drugs or to moderate their properties.

(5) Steaming
Drugs are steamed solely or with liquids to change their properties.

(6) Boiling
Drugs are boiled in water and other liquids to reduce their toxicity.

(7) Water-refining
Insoluble mineral drugs are crushed in water, the crushed particles are ground with water into fine powder in suspension. This process is repeated until no sediment of coarse particles left, then decant the supernatant water and dried.

1. Four Natures
Four natures, which are classified system of oriental medical properties according to yin-yang theory, are cold, hot, warm and cool natures of drugs. Among them, cool and cold natures belong to yin, warm and hot natures belong to yang.
In oriental medicine, harmonious and balanced physical constitutions of body is the first and foremost objective of curing.
The symptoms viewed from oriental medicine are classified into two concepts: cold symptoms('han-jeung') and hot symptoms('yul-jeung'); for cold symptoms, medicines of warm and hot natures('yang') can be used; for hot symptoms, those of cool and cold natures(yin) can be used.
For example, patients with extreme heat, extreme thirst and energetic pulse, belonging to heat syndrome of excessive type, are treated with gypsum, anemarrhena rhizome and other drugs.
If these heat symptoms are alleviated or eliminated, gypsum and anemarrhena rhizome should belong to cold nature. Warm and hot natures of drugs are determined according to the same principle.

2. five flavors

Five flavors are pungent, sweet, sour, bitter and salty tastes, which, other than doing their original functions, control the balance of body by activating or suppressing the physiological properties.
Most drugs in the oriental medicine have more than two tastes, thereby being expected to have various and more effective ways of treating.
Pungent flavour has the effects of dispersing exopathogens from superficies of the body, promoting flow of Qi and blood circulation, are used for respiratory disease such as cold or flu, blood stasis.
Sweet flavour has the effects of tonification, relieving spasm and gentling other herbs.
Sour flavor has the astringent effect of inducing astringency and arresting abnormal discharge, such as suppressing sweating, arresting bleeding, relieving diarrhea and controlling nocturnal emission.
Bitter flavor has the effects of eliminating dampness, lowering the adverse flow of qi, purging heat and relaxing the bowels and are commonly used for syndromes of pathogenic fire or damp-heat syndromes.
Salty flavor has the effects of softening and resolving hard mass and are commonly used for scrofula, goiter and others.
Tasteless flavor belongs to sweet with the effect of excreting dampness and inducing diuresis, are used for edema or dysuria.

3. Lifting, Lowering, Floating and Sinking

Lifting, lowering, floating and sinking refer to curative effects of drugs relative to the tendency of illness. Above four characteristics have their own property and are mutually conflicting; lifting and floating can be classified as 'yang'; lowering and sinking, 'yin'.
Therefore, medicines classified as 'yang' have up or outward directions of effecting; those classified as 'yin' take effect down or inward directions.
In terms of clinical treatment, the location of symptoms(upward and downward or inside and outside) is important in diagnosis and treatment; upward or outside symptoms should be cured with medicines of lifting or floating('yang'); downward or inside symptoms should be cured with those of lowering and sinking('yin').
For example, treatment by stir-baking with wine or ginger juice has the property of lifting(upward); that by stir baking with saline, lowering(downward).

※ The tendency of disease development can be downward, upward, inward or outward.
For example, downward chronic diarrhea with proctoptosis, upward vomiting with hiccup, inward exopathy with anhidrosis ,and outward spontaneous perspiration with night sweating, are all of obvious tendency of illness.

Lifting is the opposite of lowering; and floating is the opposite of sinking. Lifting means ascending and elevating; lowering means moving downward and lowering the adverse flow of Qi; floating is moving outward and dispersing; and sinking is descending and removing water retention and inducing diuresis. In general, properties of lifting upward and floating outward, have the effects of lifting Yang and arresting diarrhea, inducing sweat and dispelling exopathogens, promoting eruption and inducing vomiting, are indicated for deficiency of Qi and sinking of Qi of middle jiao, exopathy and exterior syndrome measles and rubella, and retention of toxic substnaces in the stomach. Properties of Sin king inward and lowering downward, have the effects of calming the liver, removing heat from the lung, arresting vomiting, relieving asthma, easing the bowels, inducing diuresis and stopping sweating, are indicated for hyperactivity of the liver-Yang, flarmg-up of the heart-fire, reversed flow of Qi in the lung and stomach, obstruction of urination and defecation, spontaneous perspiration and night sweating.
Lifting, lowering, floating and sinking effects of drugs are apparently linked to their natures and flavours. Generally, pungent,
sweet, warm and hot drugs mostly have lifting and floating effects; sour, bitter, salty and cold drugs mostly have sinking and lowering effects ;flowers and leaves being light mostly have lifting and floating effects; and minerals and shells being heavy mostly have sinking and lowering effects. However, there are some exceptions.
In addition, lifting, lowering, floating and sinking effects of drug are also linked to preparation, compatibility and other factors.

4. Channel Tropism

Channel tropism means what area a certain drug optionally acts on.
The theoretical basis for channel tropism, is the theory of viscera and channels(or meridians).
'kyung-rak(the channels and collaterals)' is the system that connects between inside and outside of the body. When lesion appears on the surface of body, disease can have influence on internal organs though 'kyung-rak'; conversely, when it appears directly in the organs, the effect can also have influence on the surface of the body through 'kyung-rak'.
Some groups of medicinal herbs, even showing almost the same properties in terms of botany, have their own unique property, called 'kwi-kyung' in oriental medicine, respectively when used for treatment purpose. Although all of scutellaria root, coptis root and phellodendron bark has cold nature and bitter flavor, has the same effects of purging heat and fire, they act on different channels: scutellaria root on the lung channel, treats cough for lung-heat; coptis root on the heart channel, treats insomnia for heart-fire and phellodendron bark on the kidney channel, treats nocturnal emission due to kidney-fire

5. Toxicity
Toxicity is referred to as harmful effects or toxic effects of drugs on the man body. Attention should be paid to this problem in grasping drug properties of remedies.
Poisonous are different in their toxic effects. Therefore, drugs are distinguishably marked by "slightly toxic" or "extremely toxic"in books on materia medica of all ages. In general, the toxic dose of a poisonous drug is close to its therapeutic dose with a relatively small safety coefficient in its clinical use. If used improperly, a poisonous remedy could cause severe damage to tissues and organs of the human body and even lead to death. Therefore, when using a toxic remedy, an extremely toxic one, in order to guarantee its safety dose, physicians should pay attention to the following points: