Item I say that the fever called ephemera injures the vital spirit first, and the animal spirit or the natural spirit thereafter, the which are in the humours; or the humours adjacent to them are infected, but the spirits are infected soonest, but not so that it is necessary to undertake some other operation against them, that was not done against the humours, or vice versa. It is sufficient to effect one change only, and ephemera heats it. Hence Avicenna says there is no fever therein, until fiery heat seizes the entire heart; the which is not material, as there
p.55is no peccant matter81 there in its substance to be purged by medicine. Therefore Isidorus says, in the same way purging does not necessarily avail in every sickness wherein is a peccant humour, such as causon from burnt choler.