The sphere of fixed stars
The sphere of Fixed starts
The sphere of the fixed stars. Leonardo de Piero Dati, La sfera. Wellcome Library MS 230 (mid 15th century), f.1v
Just as the planets have different properties, individual stars and constellations have different powers and influence different objects in the physical world. The 12 zodiac signs are located in this sphere. When performing surgery or blood-letting on a particular part of the body, physicians were supposed to take care that the moon was not in the zodiac sign that ruled over that part of the body or the patient would be harmed.