Problemata Aristotelis

Why do some medicaments loosen the bowels or the bladder, or neither, while others loosen the bladder but move the bowels not at all? Is it because those things that are moist by nature and filled with water, if they possess the faculty of healing, loosen the bladder? For humors that have escaped rot subside into it. Indeed, the bladder is considered a receptacle for that humor which is least digested in the stomach, which does not remain, but is excreted before it can act or suffer anything. But those that possess an earthy nature, if they have medical powers, are able to loosen the bowels. For all earthy matter rolls itself into this, and thus it disturbs if it possesses the power to move.

Why do some move the upper stomach, others the lower, such as hellebore the upper, and scammony the lower? Others, however, incite both, such as elaterium and thapsia. Is it because, of the medicaments that move the bowels, some are cold and others are warm? Thus, some, because of their heat, reach where they were in the upper stomach, seeking the upper parts and liquefying them from there, especially those things that are foreign and less seated. But also those that are by nature intimate to the medicament—that is, if it is too vehement or taken in a quantity greater than nature can bear—carry even the excrement that has grown there down into the stomach. Here, however, with heat, it disturbs the excrement and excites much flatulence, which, by resisting, vexes until it finally moves to vomiting. Others, which are cold by nature, slide downwards by their own weight, even before they perform or do anything. And starting from there, they act in the same way as the upper ones. For when they have ascended into the hidden passages and have agitated the matter in the same path, they carry with them the excrement and colluvies they have seized. And the kind of medicament that is a participant in both qualities, mixed from hot and cold, is able to do both because of its faculty; for this reason, physicians often compose medicaments with mixed genera.