There are certain well-known minor differences, in style and content, between and even sometimes within the seven books of the Epidemics in the Hippocratic corpus. But individually and as a collection they contain a wealth of detailed information about the courses and outcomes of the complaints of several hundred particular patients. Scattered through the oeuvre of Galen, and especially in his treatise Prognosis, we find Galen too describing individual cases. Given first Galen's unbounded admiration for Hippocrates, and the energy he devoted to his voluminous Commentaries on the Epidemics in particular, we might have expected Galen's case-histories to follow the patterns the Hippocratic material presented. In fact, however, his accounts of his patients diverge in several important, indeed fundamental, respects.

That discrepancy poses the chief issue I want to explore in this chapter. Why does Galen depart from Hippocratic models so radically? What is the function of the case-histories he cites in his Prognosis and of that treatise as a whole? Some parts of the answers to those questions seem to be clear and uncontroversial, but I shall also offer some speculative comments on the underlying methodological issue that I believe to be of some importance in evaluating Greek medical practice. This concerns the relationship between individual case-histories, the understanding of the signs and symptoms they contain and the generalisations offered as guides to the practitioner.