The body of man has in itself blood, phlegm, yellow bile and black bile; these make up the nature of this body, and through these he feels pain or enjoys health. Now he enjoys the most perfect health when these elements are duly proportioned to one another in respect of compounding, power and bulk, and when they are perfectly mingled.

Cure sometimes, treat often, comfort always.

First of all a natural talent is required; for when Nature opposes, everything else is in vain; but when Nature leads the way to what is most excellent, instruction in the art takes place.

Opposites are cures for opposites.

Fat people who want to reduce should take their exercise on an empty stomach and sit down to their food out of breath.... Thin people who want to get fat should do exactly the opposite and never take exercise on an empty stomach.

There are in fact two things, science and opinion. The former begets knowledge, the latter ignorance.

Medicine in its present state is, it seems to me, by now completely discovered, insofar as it teaches in each instance the particular details and the correct measures. For anyone who has an understanding of medicine in this way depends very little upon good luck, but is able to do good with or without luck. For the whole of medicine has been established, and the excellent principles discovered in it clearly have very little need of good luck.