Until the 19th century, medical astrology was commonly practiced by physicians. Each zodiac sign was believed to rule different body parts, and treatments were often timed according to planetary movements.
For example, Aries rules the head, Taurus the throat, Gemini the lungs, and so on down to Pisces ruling the feet. Doctors would avoid operating on body parts when the Moon was in the corresponding sign.
Hippocrates, the father of modern medicine, famously said: "A physician without knowledge of astrology has no right to call himself a physician."