Early-Qīng physician and literatus of Sōngjiāng 松江 / Yúnjiān 雲間 (上海); zì Qíshū 期叔 and Chénshān 辰山, hào Yúcūn 漁村. Cóngsūn 從孫 (grand-nephew) and principal medical successor of the late-Ming master Lǐ Zhōngzǐ 李中梓 (字士材, see KR3eb020). Lifedates 1628–1697 are conventional and not securely fixed; he was active from the 1640s into the 1680s. After the Ming collapse he refused civil-service career and devoted himself to medicine, travelling through Húnán (Xiāngjiāng), Hénán (Tiānzhōng), and Shāndōng (Jìshàng) for thirty years before returning south in 1666. Author of KR3eb018 Mài jué huì biàn (1664–66), which reconstructs and expands his great-uncle’s Zhěn jiā zhèng yǎn; also edited and corrected several other Lǐ Zhōngzǐ titles. Friend of Yú Jiāyán 喻嘉言, Zhāng Qīngzǐ 張卿子, and Lú Zǐyóu 盧子繇.
Name variants: 罡 (gāng) — the conventionally cited form — and the graphic variants 昰 / 是 (shì, “right / is”) are interchangeably attested in the catalog literature. The hxwd meta uses 李延是; the standard modern bibliographic form is 李延罡 (or 李延昰). No CBDB record.