It is the science of natural drugs and their physical, botanical, and chemical properties. Natural products derived from plant, vegetable, animal, and mineral sources have been a part of medical practice for thousands of years. Today about 25 percent of all prescriptions dispensed in pharmacies contain active ingredients that are extracted from higher plants, and many more are found in over-the-counter products.

Why do physicians use the symbol Rx when they write their prescriptions?

There are several explanations for the symbol Rx. One common explanation is that it comes from the Latin word recipi or recipere, which means “take” and is abbreviated as Rx. The symbol can also be traced to the sign of Jupiter, which was found on ancient prescriptions to appeal to the Roman god Jupiter. In ancient medical books the crossed R has been found wherever the letter R occurred.

Others believe that the origin of the Rx symbol can be found in the Egyptian myth about two brothers, Seth and Horus, who ruled over Upper and Lower Egypt as gods. Horus’s eye was injured in a battle with Seth and healed by another god, Thoth. The eye of Horus consisted of the sun and the moon, and it was the moon eye that was damaged. This explained the phases of the moon—the waning of the moon was the eye being damaged and the waxing, the healing. The eye of Horus became a powerful symbol of healing in the eyes of the Egyptians. In Egyptian art, the eye of Horus strongly resembles the modern Rx of the physician.