Problemata Aristotelis

Why are medicaments able to purge, whereas other, more bitter things and those marked by such qualities cannot do so? Is it because they do not possess the faculty of purging because of such qualities, but because they cannot be digested? For those things that are indigestible due to an excess of heat or cold, or because of a small body, and are fit to overcome and not be overcome by the heat of living things, and are easily resolved, can be passed from the stomach either way; these are held to be medicaments. For when they have reached the stomach and have been resolved, they are immediately carried to the veins through the same paths by which food passes. Soon, because they could not be digested at all, but have persisted with a victorious power, they slide back and drag with them that which opposes them. This process is called purging. Copper, silver, and others of the same kind, even if they cannot be digested by the heat of animals, cannot be resolved by the stomachs. Oil, honey, milk, and other such foods possess the power of purging, but by reason of quantity, not quality. For when they cannot be digested at all due to their excessive abundance, they purge, if they are able to do so. For something cannot be digested for two reasons: either because it is of a stubborn kind, or because it has exceeded measure. Therefore, nothing from the aforementioned is a medicament, since it is not able to purge because of any faculty of its own. Bitterness, sourness, and a foul odor accompany medicaments, because that class of medicaments is contrary to food. For that which has arrived and is digested by nature adheres to the bodies and is called nourishment. But that which cannot be overcome or given up, but enters the veins and disturbs them through the excess of its heat or cold, this truly possesses the nature of a medicament.

Why does pepper, if taken in large quantity, loosen the bladder, but if in small quantity, the bowels? Conversely, if scammony is taken in large quantity...