But there is still another doubt about the days themselves, because the ancients chiefly regarded the odd days, and called them critical[BC], as if on these a judgment was to be formed concerning the patients. These days were the third, fifth, seventh, ninth, eleventh, fourteenth, and twenty-first; so that the greatest influence was attributed to the seventh, next to the fourteenth, and then to the twenty-first. And therefore with regard to the nourishment of the sick, they waited for the fits of the odd days: then afterwards they gave food, expecting the approaching fits to be easier; insomuch that Hippocrates, if the fever had ceased on any other day, used to be apprehensive of a relapse.
This Asclepiades justly rejected as idle, and said that no day was more or less dangerous to the patients, by its being either even or odd. For sometimes the even days are worse; and food is given more properly after the paroxysm of the fevers: sometimes also in the same distemper the quality of the days is changed: and that becomes more severe, which had used to be more mild: and the fourteenth day itself is even, upon which the ancients laid a great stress. And when they maintained, that the eighth was of the same nature with the first, because the second number of seven began from it, they were inconsistent with themselves in not taking the eighth, or tenth, or twelfth day, as the more important: for they attributed more to the ninth and eleventh. When they had done this without any plausible reason, they passed on from the eleventh, not to the thirteenth, but to the fourteenth. It is a remark of Hippocrates too, that the fourth day is worst to him, that is to be relieved on the seventh. So that even by his own account, upon an even day both the fever may be more violent, and a sure indication given of what is to follow. And the same author elsewhere takes every fourth day to have the strongest influence with regard to both events; that is the fourth, seventh, eleventh, fourteenth, seventeenth: in which he passes from the odd to the even reckoning. Neither in this indeed has he kept to his point: since the eleventh is not the fourth, but the fifth day after the seventh. Whence it appears, in whatever light we consider the number, no true reasoning can be found in his doctrine. But with regard to these the ancients were misled by the Pythagoric numbers at that time in great vogue: whereas here as well as in other cases a physician ought not to count the days, but to consider the paroxysms themselves; and upon them to found his conjecture when food is to be given.