Bencao Yanyi Twenty volumes, written by Kou Zong-shi of the Song Dynasty. This book, also known as "materia medica", was written in the sixth year of Zhenghe (1116) and published in the first year of Xuanhe (1119). This book aims to deduce the unfinished meaning of Jiayou Bencao and Bencao Tujing, hence the name "Expanded Meaning". The first three volumes are prefaces, expounding the medical theory, proposing eight essential points for treating diseases (deficiency, excess, cold, heat, evil, internal and external), changing the traditional "four properties" (Hanre warm and cool) to "four properties". There are new insights in diagnosis, treatment, nutrition, and preparations. Volumes 4 to 20 are "Essays", and their classification and ordering are the same as Jiayou Bencao, except that "named but not used" medicines are not recorded. There are 470 kinds of medicines in the book. Those that Jiayou Bencao "have exhausted their meaning" and cannot be used will not be included. This book is in the form of notes and covers a wide range of topics, including the place of origin, form, harvesting, identification, processing of materia medica, preparations, properties, taste, efficacy, indications and contraindications of drugs, as well as Chinese materia medica drug identification and pharmacological discussion. It is particularly eye-catching. It corrects many fallacies of the predecessors and has a profound impact on the development of pharmacy in later generations. Li Shi-zhen of the Ming Dynasty commented: "Referring to the facts, verifying its rationality, citing and dialectical arguments, many inventions have been made."