Upon his untimely death, Michal Boym (1612-1659) left behind an enormous written legacy; covering a diverse range of interests in fields such as Chinese linguistics, cartography, botany, zoology, philosophy and medicine. This article attempts to examine Boym's De indiciis morborum ex linguae coloribus & affectionibus (The signs of disease on the tongue, colors and affections), a translation of a previously unidentified Chinese text. The text specifically deals with the subject of tongue diagnosis, in relation to contagious diseases that were still raging in the 17th century China. Arriving to China at the end of the Ming Dynasty (1368-1644), Boym was able to personally witness the early development of tongue examination as an independent specialty; he recognized its significance and tried to incorporate it into his ultimately unfinished Chinese medical corpus. Boym's work eventually facilitated the assimilation of tongue observation in European medicine during the 19th century.
Keywords: Chinese medicine; Jesuit mission; Michal Boym; tongue diagnosis.