[Difference and unification of the two circulatory routes of Protecting-Qi in the medical canon Lingshu]

The Moving Protecting-Qi (Wei Qi Xing), in Lingshu, one of the volumes of the Inner Cannon of Huangdi, records two types of circulatory routes which were believed to link man and nature (a traditional Chinese medicine theory that argues man is an integral part of nature). The first type of circulatory route matched the Sun and twenty-eight lunar mansions because it was believed that the Protecting-Qi circulates through different body parts of human during the day and night. This indicates that the Protecting-Qi passes through the meridians at day time and washes the five viscera at night. The second type matched the hourglass. This means it does twenty-five cycles circulation through three Yang and one Yin in the human body on a centigrade scale. The Protecting-Qi in Lingshu attempted to unify the two circulatory routes numerically by equating the two different time measures-the sun moving and the hourglass. Additionally, it implicitly took an ambiguous concept of 'Yin Fen' to replace the different parts of the five viscera, attempting to unify the two circulatory routes together. However, because of the intrinsic differences between the two circulatory routes, this effort does not make sense. It was found that the first circulatory route is mostly used in clinical practice to explain and treat disorders associated with yawning and insomnia, yet there exists a subtle difference in theoretical explanation.