The vehicle of Galen’s enormous impact on Medieval Muslim, Christian, and Jewish physicians was not only his books, which were translated from Greek into Arabic, Hebrew, Latin, and Persian, but also the so-called “Alexandrian Summaries” of his works produced in Late Antiquity. They overlap for the most part with the sixteen Galen’s treatises which were selected for the curriculum of medical studies in pre-Islamic Alexandria and in the early centuries of Islam. They do not merely shorten the originals, but show a critical attitude towards Galen’s doctrine and sometime revise it. Galen’s writings were thus transformed by deliberate intervention on the part of unnamed medical writers and sometime it was this revised Galen to enter into the medieval medical learning.