Abstract
Objectives : To examine the developmental process of the Pi-Yin theory since the Huangdineijing to Miu Xiyong. Methods : Related contents since the Huangdineijing to Miu Xiyong was searched to examine the development of the Pi-Yin theory. Results & Conclusions : In the Huangdineijing and Shanghanzabinglun, the origin of the Pi's body fluids that nurtures everywhere is explained to be the Wei, which limited the development of the Pi-Yin theory. Liu Wansu understood tonification of the Pi by means of moistening medicinals to mean adding Pi-Yin based on the manifestation of dryness in the case of dampness deficiency which is the main Qi of the Pi and Wei. Zhu Danxi understood adding Pi-Yin as accomplished by supplementing Blood. The understanding of the nature of Pi to be 'likes dryness and hates dampness' leading to thinking that drying dampness tonifies the Pi was the reason why the Pi-Yin theory could not develop fully. Miu Xiyong accepted theories of both Li Dongyuan and Zhu Danxi, and constructed the Pi-Yin theory to bring caution to the unwanted effects of using Baizhu wrongly. Through examination of the developmental process of the Pi-Yin theory, it could be understood that rather than focusing on the physiological function of the Pi-Yin and ways of maintaining its proper functioning, the theory was developed to bring caution to using medicinals with dry and hot properties that could dry the Pi-Yin.