"A question I have been haunted by is: Why 12 channels?
One aspect of the significance of 12 in the design of the acupuncture channel system and the Zang-Fu organ system of Chinese medicine is that 12 is mathematically the 'richest' number. The math of 12 indicates that it is divisible by 2, 3, 4 & 6. Thus we have two, three four and six-fold divisions of Qi which make up the acupuncture channels. But each of the 12 channels is bilateral making up a total of 24 channels. 24 is an even 'richer' number mathematically, being divisible by 2, 3, 4, 6, 8 & 12. thus in the 24 channel system we see acting the force of 1 - the Tao; the force of 2 - Yin and Yang; the force of Three - the three Dan-Tian centers of consciousness; the force of 4 - The 4 types of channel: leg yin, arm yin, arm yang and leg yang channels; the force of 6 - The six phases - the three Yin (Shao Yin, Tai Yin, Jue Yin) and the three Yang (Tai Yang, Shao Yang, Yang Ming); In the 24 channel divisions we see amplified a connection between the 8 Extraordinary channels and the 12 channels.
Yet there is another energetic that influence the channels:
To really understand the acupuncture channels we have to think of what is a human in the ancient Taoist conception of the universe. A human stands vertically in gravity, conveying the energy from the earth back up to heaven, and conveying the energy of heaven down to earth. So a human is a conveyor of two kinds of cosmic energy. The forces that descend from Heaven to Earth are said to descend as 12 branches of energy. This is in keeping with the idea of 12 astrological divisions of influence, an idea which has permeated all Asian, Indian and European thinking for thousans of years.
The forces that ascend from Earth to Heaven are called the ten stems. It is said in the Nei Jing that the 10 Stems, as they move from Earth to Heaven penetrate in through the limbs. In polarity therapy a similar understanding illuminates a series of ten channels rising bilaterally through the hands and feet. In the western esoteric traditions they are referred to as the ten Rays of consciousness.
The human is the meeting place of these forces and the acupuncture channel system arises to express the interaction of these forces, and thus they can be mapped to the physical body.
So when we talk of the 12 channels as distinct from the idea of 24 channels then we are really making a distinction about the inner part of each channel, that part which is not sided, not lateral. Fundamentally this is the divergent channel zones and the internal branches of the Yin channels. These aspects of the channel system are central rather than lateral. It is here, as the channels move between the organs, that we can trace the distinctions of the 10 stems, as they carry the yin and yang aspects of the five elements within the organ system. In this way the 10 stems interpenetrate the 12 channels at the level of the internal branches of the channels."
