Q. Why have children gravel breeding in their bladders, and old men in their kidneys and reins? A. Because children have strait passages in their kidneys, and an earthy thick humour is thrust with violence by the urine to the bladder, which hath wide conduits and passages, that give room for the urine and humour whereof gravel is engendered, which waxes thick, and seats itself, in the manner it is. In old men it is the reverse, for they have wide passages of the veins, back, and kidneys, that the urine may pass away, and the earthy humour congeal and sink down; the colour of the gravel shows the humour whereof the stone comes. 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 over-heated or roasted, turn to sand. And by this means it happens that small stones are voided, 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 reins 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 kidney 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 the 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 quality; seeing, therefore, that of its own nature it can be easily mingled, and consumed by that which it is annexed unto, 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 it in its coldness. Q. Why have we oftentime 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 filling. 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 invisible bodies in them, not by 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 contrary qualities and virtues should be hidden in mastich, and that nature hath given that virtue to these bodies.