Galen’s Commentary on Epidemics 2 is extremely helpful to us to establish and to interpret the text of Hippocrates’ Epidemics 2, although the Greek original is lost. This commentary is helpful in many ways, allowing us to compare the Hippocratic text not only with the lemmas, but also with the commentary itself and the numerous variants or discussions that date back to Galen’s predecessors. Unfortunately, Galen is rarely explicit about authorship. But his text is full of quotations from past commentators. In this paper, I will try to show through several examples how strata of earlier commentaries are sometimes traceable in Galen. Several cases of ancient discussions can be distinguished:

• All past commentators, merged into one mass, agree with each other against Capiton’s edition, allowing us to restore the original reading.
• Past commentators disagree with each other about one particular reading. Some cases are very explicit, like the famous example of the last sentence of Epid. II, 2, 20, where Galen allows us to closely follow the textual tradition.
• Past commentators disagree with each other, allowing us to restore the correct interpretation of one given reading. Of particular interest are those where we can trace a chronological review of the opinions of Galen’s predecessors. This is for example the case for the meaning of gr. thêriôdes in Epid. II, 1, 3. Such cases may become very complex if we compare the commentary on Epid. 2 to other treatises or commentaries of Galen, where he even disagrees with himself in apparently all good faith!
• Passages where Galen takes over somebody else’s saying. This is the case for an important discussion on the property of food an drink we can read in Epid. II, 2, 11. By examining this passage, I shall try to point out traces of past commentaries that might explain the wrong repetition of one sentence in the manuscripts.