What is "quartans"

Usage examples of "quartans".

Many of the sick from the inshore vessels were now aboard the Bellona and other ships of the squadron, most with fevers of one kind or another - tertians, double tertians, remittents and quartans for the most part, though there were three cases of the yellow jack - and very soon Dr Maturin was making at least his morning rounds, with Square in attendance to help him up on deck, where he would stand for half a glass or so, revelling with Jack, Tom and all hands present in the squadron's pace as the breeze came whistling in either over the starboard or the larboard bow, no longer a soldier's wind right aft as it had been the first day they sank the shore, but never heading them either, so that they beat steadily towards the Line, making legs a whole watch long.