Sino-Vietnamese Medical Exchanges and Localization as Reflected in <italic>Treatise on Medical Knowledge by Hai Thuong</italic> (海上医宗心领)

The eighteenth-century Vietnamese medical work Treatise on Medical Knowledge by Hai Thuong ( Hai Thuong Y Tong Tam Linh 海上医宗心领), authored by the eminent physician Le Huu Trac 黎有卓, reflects the transmission, application, and innovation of traditional Chinese medicine (TCM) in Vietnam. It encompasses principles, methods, formulas, medicines, clinical specialties, and clinical medical cases. Its primary textual foundation derives from Feng’s Tips and Secret Records ( Fengshi jinnang milu 冯氏锦囊秘录) by Feng Zhaozhang 冯兆张 (late Ming–early Qing), supplemented by Ming-era works such as Zhang Jingyue’s 张景岳 Jingyue’s Complete Compendium ( Jingyue quanshu 景岳全书), Li Chan’s 李梴 The Gateway to Medicine ( Yixue rumen 医学入门), and Zhao Xianke’s 赵献可 Thorough Knowledge of Medicine ( Yi guan 医贯). By synthesizing, enriching, streamlining, and annotating the quintessence of Ming-Qing medical texts, Le Huu Trac established the framework of traditional Vietnamese medicine, innovating upon TCM. Treatise on Medical Knowledge by Hai Thuong emphasizes the concept of “congenital water and fire” (先天水火), attributing the patho-mechanism of critical illnesses to the depletion of true yin and true yang (真阴真阳亏损), while expanding the indications of classical TCM formulas such as the Six-Ingredient Pill (六味丸) and Eight-Ingredient Pill (八味丸) through variations in their constituents, thus attaining the further localization of TCM. It advances the view that “there are no cold damage patterns (伤寒症) in Lingnan, rendering the Ephedra Decoction (麻黄汤) and Cinnamon Twig Decoction (桂枝汤) inapplicable,” as a result devising “three exterior-resolving formulas” (解表三方) and “six interior-harmonizing formulas” (和里六方) tailored to Vietnam’s climate and patient constitutions. The text also incorporates southern medicines (南药) and formulas containing them, using Han-Nom bilingual names to enhance understanding and application by the Vietnamese. Its Yang Case Collection (阳案集) and Yin Case Collection (阴案集), documenting both successful and unsuccessful treatments of severe illnesses, exemplify Vietnamese physicians’ local exploration and practice of Chinese medical knowledge, embodying a profound understanding and flexible application of TCM by Vietnamese physicians.