With this knowledge of herbal combinations, a herbal formula can be composed. The purpose of prescribing formulas in clinical practice is to achieve maximum therapeutic effect with minimum side effects. To practice traditional Chinese herbal medicine, practitioners are required to be able to compose formulas by themselves for treating different syndromes.

Composing a formula is a process where several conditions must be fulfilled. First, one must make a clear syndrome differentiation, establish the treatment principles, select treatment methods and figure out the most suitable strategies. One should then follow the model of formula structure, selecting appropriate herbs to play specific roles in the formula and ensuring that treatment strategies are fully expressed.

2.1. Syndrome differentiation

Clear and correct syndrome differentiation is very important for selecting a suitable treatment method and creating an effective formula. Detailed differentiation of a syndrome should include the following parts.

2.2. The treatment principle

The treatment principle takes the main syndrome in a complex condition as the target for treatment. In the process of treatment, the syndrome will change and the treatment principle will thus change too. For instance, in a syndrome of Liver-Yang ascending and generating Liver-wind, the treatment principle should be to intensively and quickly descend Liver-Yang and extinguish Liver-wind. Once the Liver-Yang has returned to its original place and the Liver-wind has disappeared, a syndrome of deficiency of Spleen-Qi and stagnation of Liver-Qi may then become the main syndrome. The treatment principle should change to that of spreading the Liver-Qi and strengthening the Spleen.

2.3. The structure of a formula

Following the treatment principle, which is established in accordance with the syndrome differentiation, a formula can be composed. A formula is neither a group of herbs that treat all symptoms nor a combination that only treats the main syndrome. It has a structure where herbs are organized in order to meet the needs of the treatment. The structure of a formula contains four parts, namely: the chief, the deputy, the assistant(s) and the envoy. Each of these has specific functions in the formula.

Chief (Zhu , Jun )

The chief is the ingredient that directly treats the principal syndrome, which is manifested by the main symptoms.

The chief can be one ingredient, but it can also be a herbal combination. Generally speaking, the chief has a relatively large dosage within the formula as a whole, and it enters the meridians where the pathological changes are manifest.

Deputy (Fu , Chen )

• The deputy is the ingredient that has the function of accentuating and enhancing the effect of the chief ingredient to treat the principal syndrome.

• The deputy serves as the main ingredient acting directly against a coexisting syndrome.

The deputy can be one herb, a herbal combination, or several groups of herbal combinations, according to the needs of treating the principal syndrome and the coexisting syndromes.

Assistant (Zuo )

• The assistant accentuates and enhances the therapeutic effect of the chief or deputy ingredients, or directly treats secondary symptoms. The ingredient that has this function can be considered a helping assistant.

• The assistant moderates or eliminates the toxicity or harsh properties of the chief or deputy ingredients. The ingredient that has this function can be considered a corrective assistant.

• The assistant has a function or a moving tendency which goes against the chief ingredient but which is helpful in fulfilling the therapeutic effect and which may be used in complicated and serious conditions. The ingredient that has this function can be considered a strategic assistant.

Since this role may require a range of actions, there are often several herbs or herbal combinations acting as assistants in any one herbal formula.

Envoy (Shi )

The envoy serves as a guide to bring the rest of the herbs into the meridian or region where the main pathological change exists, allowing their actions to focus on this specific region. In most cases, the chief carries out this function as it must enter the place where the pathological change is located.

The envoy harmonizes and integrates the actions of the other ingredients in order to balance the action, temperature, speed and direction of the formula.

(See Figure I.2 on page 34.)

2.4. Principles, methods and strategies of selecting appropriate herbs when composing a formula

In order to compose effective formulas, the principles, methods and strategies of selecting herbs are very important. They enable a practitioner to compose formulas to treat a variety of syndromes. The principles, methods and strategies introduced in each chapter of this book are abstracted from a large number of formulas, integrating the knowledge of single herbs, herbal combinations, syndrome differentiation, treatment methods and treatment sequence. They are the essential part of this book.

Before composing a formula, the relevant syndrome is first identified. The syndrome is analyzed and divided into the principal syndrome and the secondary syndrome, which are manifested in the main symptoms and the secondary symptoms, with specific signs on the tongue and the pulse. These are the first steps in selecting the appropriate herbs to fulfill different roles in the formula. Moreover, the syndrome analysis evaluates the development of the disorder of the internal organs with regard to the pathological change. This provides another clue to assist the selection of the herbs in the formula. For instance, if Liver-Qi stagnation is diagnosed, it follows that the Liver can easily attack the Spleen, so in the formula some herbs that strengthen the Spleen should be prescribed. Similarly, if the patient has a Yang constitution, the stagnation of Liver-Qi can quickly generate Liver-fire, so some herbs that prevent the generation of fire or prevent the heat becoming strong should be added as well. In a condition of excess heat in the Lung, one should be aware that strong fire can easily consume both the Yin and the Qi, so one should not only prescribe herbs to reduce fire, but also herbs that nourish the Yin and tonify the Qi.

Next, an appropriate treatment principle to treat the presenting syndrome is established. For example, to treat an excess heat syndrome in the Lung, the treatment principle is to reduce the heat, nourish the Yin, regulate the Lung-Qi and, at a later stage, strengthen the Lung-Qi.

As soon as a treatment principle is established, the composition plan and treatment strategies can be arranged. For instance, to treat the syndrome of excess heat in the Lung and Stomach, one would first prescribe herbs that have sweet-cold, bitter-cold or salty-cold properties, and which have the functions of clearing heat and reducing fire in the Lung and Stomach. Second, herbs that are sweet and cold and that can nourish body fluids and protect the Yin, which has been severely consumed by the excess heat, should be selected. Herbs that can tonify the Qi should be selected if the Qi is weakened severely by the heat. Herbs that moderate the actions of the harsh herbs in the formula, and reduce their side effects, should also be added.

The composition plan and the treatment strategies are effected by appropriate herbs, which are selected carefully according to their properties, functions and characteristics. Take again the treatment of excess heat in the Lung and Stomach as an example. Shi Gao ( Gypsum) is selected as the chief in the formula because it has cold, sweet and pungent properties, enters the Lung and Stomach meridians and can directly and intensively reduce excess heat in the Lung and Stomach. Zhi Mu ( Anemarrhenae rhizoma) is selected as deputy because it is moistening and cold. On the one hand it can accentuate the function of Shi Gao to reduce the excess heat; on the other hand it can nourish the Yin, which has been badly damaged by the heat, thereby directly treating the secondary syndrome. Gan Cao ( Glycyrrhizae radix) and Jing Mi (non-glutinous rice) are selected as assistants to tonify the Qi of the Spleen and to protect the Stomach from injury by the pathogenic heat and the bitter, cold and heavy herbs.