When one peruses medical case histories from the Qing dynasty, one sees constant references to phlegm (tan痰) as both cause and consequence of disease. Phlegm figures as a central, indispensable concept in the late imperial Chinese imagination of the body and its pathologies. Curiously, however, the Huangdi neijing 黃帝內經 (ca. 1^st cent. B.C.), the earliest and foundational classic of Chinese medicine, does not mention the term tan痰 at all. How did the Chinese concept of phlegm develop, and what does it mean?

In this lecture I trace the rise of phlegm in China and show that its development plays an important part in fundamental changes in Chinese medical theory after the classical period. Studying phlegm in the longue durée allows me to highlight two related and rarely discussed facets of Chinese medicine: (1) the historical connections of Chinese medicine with other major contemporary medical traditions (2) the importance of fluids and fluid-based therapies in Chinese medicine. They allow for meaningful comparisons of Chinese medical concepts and practices with contemporary humoral traditions in India, Europe, and the Islamic world.