Apart from its role in the development of clinical medicine, Galen's Commentary and its Arabic translation are important for a number of reasons:

• They preserve old and original readings of the Hippocratic Epidemics and offer significant interpretative tools for understanding this difficult work. The textual transmission of the Hippocratic Epidemics poses a number of problems. Robert Alessi (1996, 39), who is currently preparing an edition of the Hippocratic Epidemics for the Budé series, points out that the lemmata in Ḥunayn's version go back to a tradition uncontaminated by the Hippocratic text (as was the case in the Greek tradition) and concludes: "one can thus appreciate the crucial importance of Galen's Commentary, not only for establishing the text of the second book of Hippocrates' Epidemics [which is only extant in Arabic], but also for their interpretation." (p. 50).
• They contain many quotations of earlier Greek authors which are preserved only fragmentarily such as the famous physician Diocles of Carystus (fl. 4th century BCE). In his edition of the fragments of Diocles, Philip van der Eijk (2000–2001, I 258-9, fr. 159) drew on Ḥunayn's hitherto unpublished Arabic version and noted how unsatisfactory Pfaff's German rendering was (II 297).
• As the longest commentary on any Hippocratic text by Galen (ca. 350,000 words in the Arabic), it is important in its own right both for understanding Galen's approach to the Father of Medicine and Galen's own medical theory and practice. It is well-known that Galen shaped Hippocrates in his own image by establishing which Hippocratic works were genuine and merited his attention — usually those which suited his own medical theories — and which ones did not. The Commentary therefore represents an important source for Galen's thought.
• The Arabic translation of Galen's Commentary is a crucial witness to the Graeco-Arabic translation movement of ninth-century Baghdad. It is one of the few texts that can be attributed to Ḥunayn ibn Isḥāq with nearly absolute certainty. This famous translator single-handedly shaped the medieval Arabic medical language which was used for centuries to come. A study of his translation technique promises to uncover crucial information about the formation of Islamic medical theory, but also to contribute to Graeco-Arabic scholarship in general.
• In the medieval Muslim world, case notes became a significant resource for medical research. Cristina Álvarez-Millán (1999, 2000) has shown that al-Rāzī, the greatest clinician of the Middle Ages, was heavily influenced by his Greek predecessors. It is evident that the Hippocratic Epidemics and Galen's Commentary played a crucial role in the development of clinical medicine in the lands of Islam, notably in the Islamic hospitals in the Abbasid capital Baghdad.
• Galen's Commentary on the Epidemics also served educational purposes in the Islamic world. Ḥunayn ibn Isḥāq wrote an abridgment in question-and-answer format, and we also have several summaries from other authors. Moreover, Ibn al-Nafīs, celebrated for the discovery of the pulmonary transit, wrote an as yet unpublished commentary on the Hippocratic Epidemics.

In general, the influence of the Arabic version of Galen's Commentary on the Hippocratic Epidemics on medieval Islamic medicine can hardly be overestimated. Editing this important source will provide historians of medicine with a text that not only helped establish clinical medicine in the East but went on to serve as a bridge between medical research and practice in the Islamic world and the Latin West.

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