Q. Why is it, if the stone do congeal and wax hard through heat, we use not contrary things to dissolve it by coldness, but light things, as parsley, fennel and the like? A. It is thought, to fall out by an excessive scorching heat, by which the stones do crumble into sand, as in the manner of earthen vessels, which, when they are overheated or roasted, turn to sand. And by this means it happens that small stones are avoided, together with sand, in making water. Sometimes cold drink thrusts out the stone, the kidneys being stretched and casting it out by a great effort; thus easing the belly of its burden. Besides, it often happens that immoderate heat of the kidneys, or of the veins of the back (through which the stone doth grow) is quenched with coldness. Q. Why is the curing of an ulcer or bile in the kidneys or bladder very hard? A. Because the urine being sharp, doth ulcerate the sore. Ulcers are worse to cure in the bladder than in the kidneys, because urine stays in the former, but runs away from the latter. Q. Why do chaff and straw keep water hot, but make snow cold? A. Because the nature of chaff wants a manifest quantity; seeing, therefore that of its own nature, it can easily be mingled, and consumed by that which it is annexed onto, it easily assumes the same nature, and being put into hot things, it is easily hot, heats again, and keeps hot; and on the contrary, being made cold by the snow, and making the snow cold it keeps in its coldness. Q. Why have we oftentimes a pain in making water? A. Because sharp choler issuing out, and pricking the bladder of the urine, doth provoke and stir up the whole body to ease the part offended, and to expel the humour moderately. This doth happen most of all unto children, because they have moist excrements by reason of their often drinking. Q. Why have some medicines of one kind contrary effects, as experience proves; for mastich doth expel, dissolve and also knit; and vinegar cools and heats? A. Because there are some small invisible bodies in them, not in confusion, but by interposition; as sand moistened doth clog together and seem to be but one body, though indeed there are many small bodies in sand. And since this is so, it is not absurd that the contrary qualities and virtues should be hidden in mastich, and that nature hath given that virtue to these bodies. Q. Why do nurses rock and move their children when they would rock them to sleep? A. To the end that the humours being scattered by moving, may move the brains; but those of more years cannot endure this.