Eighteenth-century Korea saw an emergence of the medical case history genre, and the most noticeable example of it was Yeoksi manpil 歷試漫筆 (1734), written by Yi Sugi 李壽祺 (1664–c.1750). This paper analyzes Yeoksi manpil to bring to light a new medical landscape of late Joseon Korea, while situating it under the context of the history of science and ideas in Korea. Yi Sugi was a new kind of historical actor, hailing from the group of jung’in 中人 technical officials, a group which was newly emergent in the late seventeenth and early eighteenth centuries. As a jung’in medical official, he tried to secure his professional identity, in a way that might enhance his cultural sensitivity toward tools or technology. My argument goes that in the stage of medical practice, Yi Sugi had enacted such tools as pulse (脈), materials (物), circumstance (情) on top of symptoms (症). This kind of activity might be called a medical innovation in practice to the extent that other doctors of the period concerned themselves mostly with symptoms. In conclusion, the medical practice as represented by Yi Sugi and his medical work Yeoksi manpil gives an illustrative example showing that eighteenth-century Korea was a dynamic cultural space in which people, knowledge, tools/technology, materials, and practice were actively being interconnected and culturally redistributed.