On the title page of a Paris manuscript containing the Arabic translation of Galenic treatises, a later hand has added a division of medicine. This division draws on material related to Galen’s On Sects and Therapeutics to Glaucon but cannot be linked to any particular model preserved in Greek. However, it shows remarkable parallels to the most famous introduction to medicine in Arabic, that is, Ḥunayn ibn Isḥāq’s Medical Questions, and appears, almost verbatim, at the beginning of Ibn al-Ṭayyib’s Résumé of the Alexandrian Summary of On Sects. The article presents an edition and translation of this division of medicine, and studies its relations to other divisions preserved in Greek, Latin and Arabic. The conclusion that suggests itself is that the ultimate source of the division at stake goes back to Late Antiquity.