For generations, healers and physics (an early term for physicians) used natural cures that worked wonders for their patients. Little did they know, the cures were based on scientific principles of chemistry that wouldn't be verified for hundreds of years. They only used what worked.
One of the medieval cures for cleansing a wound involved calcium carbonate. Called "quicklime," it was made from crushed shells or bones. The quicklime was added to salt or a sodium-rich plant, with a little dry mustard (a powerful astringent). Healers would wash the wound in hot beer--beer being far more hygienic and reliably sterile than water--and then scrub the area with the quicklime and salt mix. For the final step, they coated the would with a vegetable oil and pulverized fir, another proven astringent that also helped form scabs.
There is sound chemistry behind this cure. The calcium carbonate, salt and oil formed an impromptu soap on the skin, keeping the wound clean. Ta-dah! Science!
Trial-and-error science was not limited to cures; nutrition also benefited. One medieval means of cooking involved a double boiler. Cooks would bundle cool, thickened leftover pottage (porridge) in a linen cloth, a large ball of ground meat in another, and a selection of vegetables in a third. The packets were layered on top of one another in the smaller pot, pottage on the bottom, then meat, then vegetables. Cooks would pour broth in the larger pot of the double boiler, assemble it, and let it simmer for hours--a medieval crock pot.
What was so ingenious about this method, aside from saving time and keeping food warm until it was needed, is that is wasted nothing. Healthful vitamins released by the vegetables were simply collected in the double boiler, invigorating the broth with much-needed nutrients, while the boiling, swirling broth kept the food moist, gave everything a nice flavor, and slowly steamed the vegetables--no wiggly veggies! They might not have known it was a healthy thing to do, scientifically speaking, but record of this method of cooking shows that medieval citizens knew they were better off eating from multiple food groups and not overcooking vegetables.
Over the years, cures and techniques such as these were scrutinized by science and proven sound. People of old might not have known how it worked, but they benefited nonetheless. Now if only someone had been around to tell them that mercury worked so well as a diuretic because it was slowly poisoning the body...