This article probes into the Organon manuscripts Oxford, Bodleian Library, Auct. T.4.23 (Misc. 261) and Barocci 87, which belonged to the physician and scribe Demetrius Angelus (Constantinople, 15th c.). It discusses those codices’ formation, circulation as a multi-layered set of two volumes, and later modifications. Finally, the paper examines the First Analytics text in the Baroccianus and places it in the pertinent place within the tradition of this treatise.