The Hippocratic Epidemics and Galen's Commentary are milestones in the development of theoretical and clinical medicine. The Hippocratic text contains numerous case notes describing in detail the development of various diseases in real patients. Its authors' observations display an acute sense of perception and attention to detail, and they paid particular attention to the individual circumstances of their patients and environmental conditions. It is therefore not surprising that Galen, the greatest physician of antiquity, chose to comment on them with great care. He did, however, maintain that not all books of the Epidemics could reliably be ascribed to the historic Hippocrates; in his opinion, Books 1 and 3 were genuinely Hippocratic while 2 and 6 consisted of Hippocratic notes that vary greatly in style and content and were compiled after Hippocrates' death. Galen decided to comment only on these books, which he regarded as fully or at least mostly genuine.
Scholars at different times throughout history were fully aware of the importance of the Hippocratic Epidemics and Galen's Commentary, especially, it would appear, those concerned with clinical medicine rather than medical scholasticism. In ninth- and tenth-century Baghdad, an environment which saw the rise of sophisticated hospitals, Hunayn ibn Ishaq translated Galen's work into Arabic. He also wrote a treatise in question-and-answer format in which he re-packaged the contents of Galen's Commentary to make it more digestible for students. Other, later medical experts such as Abu Bakr Muhammad ibn Zakariya al-Razi (Rhazes, d. c. 925) and Ibn al-Nafis (d. 1288) held the Epidemics in high esteem. The former used it in conjunction with Galen's Commentary as a model for his own clinical work (Álvarez-Millán 1999, 2000). Not surprisingly, some of al-Razi's most innovative medical research is based on information contained in Galen's Commentary on the Epidemics (Pormann 2008). Ibn al-Nafis, who famously discovered the pulmonary transit in defiance of Galenic orthodoxy, also composed a commentary on the Epidemics (Bachmann 1971, Abou Aly 2000). One of the manuscripts used in our project (ms. E) bears witness to the attention of a Jewish physician who read Galen's Commentary and wrote short titles or summaries in the margins of his copy in Judaeo-Arabic (i.e. Arabic written in Hebrew letters). Despite the long-lasting interest in the text in the Western and Islamic worlds, no complete copy of the Greek original of Galen's Commentary survives.
Fully aware of the deficits of the Greek tradition, the Scottish scholar David Colville in the 1620s carefully copied out those parts of the Arabic translation not extant in Greek (resulting in ms. M; cf. Löfgren and Traini 1975-95: i. 66-67, no. 105). Roughly a century and a half later, the celebrated Arabist Michael Casiri (1760-70: i. 249-257, nos. 800-1) quoted extensively from the Arabic translation and noted its crucial importance, as did the famous German philologist Johannes Mewaldt, who wrote: "Given the serious deficiencies of the Greek manuscripts [of Galen's Commentary], we have to be glad that this [Arabic] translation has come down to us […]" (CMG V 10,1: xxii). A leading figure of Graeco-Arabic studies in the early 20th century, the German physician Max Simon, undertook to edit and translate the Arabic version but passed away before finishing this task. Another German, Franz Pfaff, continued Simon's work. When Ernst Wenkebach edited the Greek text of Galen's Commentary for the Corpus Medicorum Graecorum (as CMG V 10,1 and V 10,2,1-2), he called on Pfaff to provide him with a German translation of the Arabic version, both to improve the Greek where it is extant and to supplement it where it is not. Pfaff drew on Simon's previous efforts; his original aim was to publish the Arabic text alongside a revised German translation, but the economic circumstances of 1930s Germany did not allow for the then costly printing of the Arabic. Pfaff ended his preface by saying: "To fulfil the requirements of rigorous scholarship, the Academy intends to print the Arabic text at a later date, once the economic situation allows to cover the expense." (CMG V 10,1: xxxiii) This wish is now being fulfilled.