Dong Yuanzi's Inner Elixir

This book uses Bagua knowledge to explain the physiological functions of the body and changes in yin and yang, and discusses the qi transformation of the human body under the state of Qigong. There are 21 sections in the book. The first section discusses Xuanyuan, which is the outline of the book. The following sections discuss the mutual roots of Yin and Yang, the changes and relationships between Yin and Yang, to explain the functional changes between various parts of the body. It also explains the basic concepts of intercourse, Yuanhuo, bathing, mother and child, holding Yuan, keeping a number, divine light, and general Guangxuan. The book ends with the Guangxuan section, emphasizing that practicing Qigong is aimed at the changes of Yin and Yang in each period of the body. To make up for the deficiencies, there is more than enough to make up for the losses. "Hold the essence and keep the unity."