 They were responsible for the relief of sick or wounded seamen; at first the relief they provided was of an improvised nature.The Royal Greenwich Hospital, a home for superannuated seamen, had only a limited number of places for invalids; no naval hospitals were especially built until the middle of the eighteenth century, though hospital ships were employed intermittently from at least as early as the mid-seventeenth century.On board ship surgeons with warrant rank had been carried since the seventeenth century .