Lǐ Dōngyuán 李東垣 (real name 李杲 Lǐ Gǎo, zì Míngzhī 明之, hào Dōngyuán lǎorén 東垣老人, 1180–1251), Jīn-Yuán physician of Zhēndìng 真定 (Héběi), disciple of Zhāng Yuánsù 張元素, and one of the Jīn-Yuán sì dàjiā 金元四大家. Founder of the Bǔtǔ pài 補土派 (Supplementing-the-Earth / Spleen-Stomach School). Principal works: Pí wèi lùn 脾胃論, Nèi-wài shāng biàn huò lùn 內外傷辨惑論, Lánshì mìcáng 蘭室秘藏. His signature formula Bǔzhōng yìqì tāng 補中益氣湯 became foundational to late-imperial spleen-stomach therapeutics.