Chén Yánzhī 陳延之, mid-fifth century (fl. c. 454–473), is the otherwise-unidentified author of the Xiǎopǐn fāng 小品方 (also called Jīngfāng xiǎopǐn 經方小品), KR3ed006. Nothing about Chén is recorded outside of his own preface — no native place, no exam history, no offices, no biographical sketch in the standard histories — but the preface’s internal evidence is enough to date him with some precision. He cites the Sìbù shū mùlù 四部書目錄 of the Imperial Secretariat as the source for his pre-existing-medical-text inventory, fixing him no earlier than the LiúSòng. His citation of Fàn Wāng 范汪 (Fàn Ānběi 范東陽 / 范安北, 308–372) as a recent source and of Yáng Zhōngsǎn 羊中散’s compilations of the 元嘉 reign (424–453) places him no earlier than the Yuánjiā era; his work is in turn quoted in the Wài tái mì yào (752) and the Yī xīn fāng (984). Modern scholarship (Mǎ Jìxīng, Liào Yùqún, Kosoto Hiroshi, Mayanagi Makoto) places his floruit in the Xiàojiàn / Dàmíng / Tài shǐ eras of Sòng Xiàowǔdì and Míngdì, i.e. c. 454–473.
He is the principal theorist of the yìngsuí 應隨 principle — the doctrine that recipes cannot be applied mechanically but must be adapted to each patient’s age, sex, regional climate, constitution, and seasonal qì — and the most important Chinese medical bibliographer between the Hànshū yìwénzhì and the Suíshū jīngjízhì. He is not in CBDB.