This article continues the analyses in Medical History 52 (2008), 73–90, 365–86 of William Harvey’s self-understanding as the philosopher and discoverer of the blood’s circulation. Harvey brilliantly and subversively assumed the persona of the mythological Hercules to embody his own anatomical labour in De motu cordis et sanguinis (1628). He reprised the role in self-defence against accusations in the College of Physicians, London, of his breach of faith with medical tradition. Harvey sought to usurp the medical epithet ‘a second Hercules’ by reforming humanist dependence on ancient texts as authoritative medicine. A knowledge of the theory and practice of Renaissance humanism discloses his identification with the Herculean labour of cleansing the Augean stable. He employed anatomical demonstration against Galen’s porous cardiac septum, which admitted blood across the ventricles. Harvey’s oath mehercule swore against Galen’s Dia to assert the necessity of opening an alternate route for the blood flow. His Herculean labour was to dam the cardiac septum and divert the blood flow into a continuous channel through the arteries and veins. His circulation of the blood also imitated Hercules’ successful dependence on the force of the water flow to flush the Augean stable. Harvey’s copia did not denote a quantitative amount but a powerful supply. Harvey aspired to be, like Hercules, immortal, a term which the College belatedly acknowledged. This cultural analysis exposes Harvey’s professional issues and personal ambitions, so to promote a fuller understanding of his historic role in medical discovery.