Zhāng Yuánsù 張元素 (zì Jiégǔ 潔古, ca. 1131 – ca. 1234, 金), Jīn-period physician of Yìzhōu 易州 (modern Yì xiàn, Héběi), and the founder of the Yìshuǐ school (易水派) — the third great JīnYuán medical school alongside Liú Wánsù’s Héjiān school and Zhāng Cóngzhèng’s Gōngxià school. Took the imperial-examination tóngzǐ jǔ at age 8 and the jìnshì exam at 27, but failed when he taboo-violated an ancestral-temple character — turning thereafter to medicine, which he mastered through study and reflection. Author of: Yī xué qǐyuán 醫學啟源 (Origins of Medical Learning, the foundational Yìshuǐ school work — not separately catalogued in this Kanripo division but a major JīnYuán medical theoretical work); Bìngjī qìyí bǎomìng jí 病機氣宜保命集 (KR3e0050, 3 juan in 32 gates) — the present work; Zhēnzhū náng 珍珠囊 (a materia-medica work). Famous for the apocryphal anecdote of his successful diagnosis of 劉完素 Liú Wánsù’s own 8-day cold-damage illness when other physicians had failed, recorded in Lǐ Lián 李濂’s Yīshǐ 醫史. Zhāng’s chief disciple was 李杲 Lǐ Gǎo, the founder of the Spleen-and-Stomach school. The catalog meta gives the dynasty as Jīn; this is correct.