Hippocrates De prisca medicina 17

[17] One might here say—but persons in ardent fevers, pneumonia, and other formidable diseases, do not quickly get rid of the heat, nor experience these rapid alterations of heat and cold. And I reckon this very circumstance the strongest proof that it is not from heat simply that men get into the febrile state, neither is it the sole cause of the mischief, but that this species of heat is bitter, and that acid, and the other saltish, and many other varieties; and again there is cold combined with other qualities. These are what proves injurious; heat, it is true, is present also, possessed of strength as being that which conducts, is exacerbated and increased along with the other, but has no power greater than what is peculiar to itself.

[17] An opponent may retort, But patients whose fever comes from ardent fevers, ¹ pneumonia, or other virulent disease, do not quickly get rid of their feverishness, and in these cases the heat and cold no longer alternate. Now I consider that herein lies my strongest evidence that men are not feverish merely through heat, and that it could not be the sole cause of the harm; the truth being that one and the same thing is both bitter and hot, or acid and hot, or salt and hot, with numerous other combinations, and cold again combines with other powers. ² It is these things which cause the harm. Heat, too, is present, but merely as a concomitant, having the strength of the directing factor which is aggravated and increases with the other factor, but having no power ³ greater than that which properly belongs to it.