Irish men and women made up more than a quarter of the approximately one hundred and sixty thousand convicts transported from the British Isles to Australia in the period 1787-1868. They feature, in major accounts of early New South Wales, as irredeemably shiftless, and prone to escapism. And in the medical literature of convict transportation, this characterization sometimes intersects with another, specifically pathological, impression: the Irish, on account of their "habits" and "character," appeared uniquely predisposed to scurvy. This essay explains how this intersection was established, by ships' surgeons and others, via reference to theories of constitution, which had their roots in Hippocratic thought but were revitalized and revised in eighteenth-and early nineteenth-century maritime and colonial contexts. In the literature of colonial Australia, indolence, illness, and Irishness often appear as conjoined energies, suggesting the importance of pathology and its sources—apparent or actual—for the constitution of New South Wales.