Herbs were used as a medicine. Plants gathered from different locations varied their ability to cure illnesses. different parts of a plant contain varying levels of effective compounds. Different times of the year (seasons) also can change the amount of plant needed to produce an appropriate dose. Salicylic acid (from willow tree and meadowsweet plant common throughout Europe) was known before Bayer and Company began marketing aspirin. The root of wild celery was prescribed to prevent muscle cramps. Parsley was believed to induce a miscarriage. Ivy was used to relieve symptoms of asthma. Digitalis ( extract from foxglove Digitalis Purpurea) contains molecules that have been known to have a powerful effect on the heart (Cardiac glycosides). These molecules reduce heart rate, normalize heart rhythm, and strengthen heartbeat. An example of cardiac gycosides is the digoxin molecule. In 1975, a British physician named William Withering used extracts of foxglove to treat congestive heart failure after hearing rumors of the plants curing abilities. It was well over a century before chemists were able to identify the molecules that were responsible. The structure of a digoxin molecule is simple. There are three sugar units that are different from those in the sarsaparilla or Mexican yam plants. The digoxin molecule lacks the OH group on the steroid ring system. Foxglove is still the main source for today's drug. Ancient Egyptians and Romans used an extract from the sea onion as a heart tonic and rat poison ( if in larger doses). The sea onion also contains a different cardiac glycoside molecule. Toxic compounds that have a similar structure to cardiac glycoside olecules can be found in animals.They do not contain sugars. They are conclusive poisons and of little medical value. The source of these venoms is amphibians. Extracts of toads and frogs have been used as poisons in many parts of the world. The toad (after the cat) is the most common animal in folklore as a familiar to a witch. Many potions that have been made by "witches" were said to contain parts of toad. The molecule Bufo-toxin is the active component of the common European toad, Bufo vulgaris. It is one of the most toxic molecules ever known. Its structure shows some similarity to the steroid ring system to the digitoxin molecule.