The title of this book is often shortened as Nan Jing (Canon on Eighty-One Difficult Issues) which waswritten in conversation. Traditionally it was believed that this book was compiled by Qin Yueren (also known as Bian Que), a great doctor in the Warring States. Now it is generally agreed that this book was compiled in the late Western Han Dynasty. The main proof is that it was not mentioned in Qi Lue (七略). The first time it was mentioned was in the preface to Shang Han Za Bing Lun (Treatise on Cold Diseases and Miscellaneous Diseases) written by Zhang Zhongjing in the Eastern Han Dynasty.
The 81 questions asked in Nan Jing (Canon on Eighty-One Difficult Issues) concern with pulses, Channels, zangfu-organs, diseases, Acupoints, acupuncture and moxibustion.
The main difference between Nan Jing and Huang Di Nei Jing is that Nan Jing, unlike Huang Di Nei Jing that discussed yin-yang and Wu Xing separately, studied medicine by combining the theories of yuan qi (primordial-qi), yin-yang and Wu Xing and, by applying pulse diagnosis, Channels, zangfu-organs, manifestations of diseases, Acupoints, acupuncture and moxibustion, establishing a system of theory without making direct use of empirical knowledge. For example, the ten kinds of pulse changes were resulted from the variations of sturdiness and softness (yin and yang) of the Wu Xing.
As to the Acupoints,each Channel possesses five special Acupoints known as Jing-Well, Xing-Spring, Shu-Stream, Jing-River and He-Sea respectively. These five Acupoints share the attributes of Metal, Wood, Water, Fire and Earth respectively. There exists a promoting order among these five Acupoints according to the theory of Wu Xing. The order of the restricting relationships between the Acupoints with the same names located on the yin and yang Channels is described in the following table. In treating diseases, doctors select Acupoints according to the promoting and restricting attributes of the Wu Xing. These attributes were first mentioned and discussed in Nan Jing, playing an important role in modern science of acupuncture and moxibustion.