These are two fevers and since the cause of a species69 of hectica is ephemera, we should rightly speak of it first according to Averroes. Ephemera is so-called, because efemiron in Greek is the same as a certain fish in Latin, the which fish70 is only alive for one single day; and in the same way this fever does not continue beyond one day in its own course. Ephemera is a fever resulting from exceptional immoderation of the spirits71 which does not last beyond twenty four hours, as regards its own nature. And therefore note, there is true ephemera, and false: the true ephemera does not continue beyond a natural day without finishing; the false continues at times till the third and at other times till the fourth day, and the cause of it is the grossness of the matter in the body, or the blocking up of the pores, the which prevents opening; or because of the oppilation of the pores from an external cause.