Owen Powell is the latest in a long line of scholarly doctors who have interpreted the works of Galen for later practitioners and readers. Oribasius in the fourth century and Kühn in the nineteenth are two of the most famous, but behind these two lie many others who commented upon, translated or commissioned treatises or excerpts that still, in some cases, survive as manuscripts and printed books. All these doctors continue the work that Galen himself set in place as he tried to make the texts of the Hippocratic and Hellenistic doctors work for his own time. Powell in his introduction and commentary describes clearly the physiology of Galen's digestive system, and how that system compares with human digestion as now understood by medical science. Galen does not explain his system in full in this treatise, but refers to it in the introductory chapter and at various later points. It is a feature of the work to define its terms of reference and direct the reader elsewhere if an item falls outside those guidelines. I return below to navigational aids provided by Galen in his text. The purpose of this foreword is to complement Powell's introduction by exploring some points that he makes only in passing. The two major areas I aim to address concern the social and cultural world in which Galen was writing and the methods he used in attempting to collect and classify foods in the treatise.