Medical astrology was based on the belief that the body’s “microcosm” corresponded to the “macrocosm” of the planets and stars and gave order to the seemingly random course of life and health. Thus, it assisted the physician in
prescribing treatment, in predicting the course of a disease, and in casting horoscopes.  

The twelve Zodiac signs below cover the body from head (Aries) to toe (Pisces) because Aries is the first sign of the zodiac while Pisces is the last. Physicians diagnosing an illness would determine the constellation that the moon appeared in when the patient first became ill. He would then consult astrological predictions and associations and make a diagnosis.