There are many characters used for the vital function of free-flow of blood and qi throughout the body, but the most important and commonly used is tong (通).
The character tong (通) describes any kind of communication which is free from obstruction; it is particularly used for the spreading and free movement of qi, but can describe communication between people as much as free-flow within the organism. In classical Chinese it is to open the way, to open dialogue, to allow the mingling of different things, ideas, people. It is to give free access to something; to penetrate and to permeate.
The radical of the character (辵/辶) is to walk, in a measured and rhythmical way – which is very similar to the character xing (行) – the xing of wu xing (五 行), the five phases or elements. Both have the same idea of regular and well-regulated movement. The easy flow of one thing into another. The character xing (行) is used to describe the regular movement of the heavens (the movement of the stars and planets is xing xing 星 行), and tong has the added dimension of the even distribution of qi which is made possible by this perpetual movement.
The same radical is seen in the character for dao (道) which, as well as its more philosophical meanings of the way, the way things are, the ways things move and change and transform, is also seen within physiology to imply movement and free-flow. The character dao is often used to describe the movement of water, and is seen in the point name shui dao (St 28), and also the free movement of the spirit/consciousness, as in shen dao (Dumai 11) and ling dao (Ht 4).
The character tong is found in the point names of Gallbladder 7 tong tian (通 天), communication with heaven, and Heart 4, tong li (通 理), communication with the interior. This tendency to use the character tong in association with heaven, the spirits and the heart, suggests the importance of this constant movement, circulation and communication within the psyche as well as the general physiology. In the philosophical classics tong dao (通 道) and tong xuan (通 玄) are common terms for understanding the dao and penetrating the mystery of life.
Therapeutically, tong is to restore the movement and circulation of qi wherever there is blockage and restriction. Bu tong (不 通) suggests the lack of free circulation – the main cause of disease and dis-ease. Tong bu tong (痛 不 通) is a common expression which is used to describe pain (tong 痛) due to blockage – the character for pain sharing the same phonetic (甬) with the added radical for illness (疒).