Amulets symbolizing the uterus and the mechanics of the womb offer divine protection for pregnancy and childbirth. They display engravings of Egyptian deities such as Anubis, Chnoubis, Harpocrates, and especially Isis, the goddess of fertility and motherhood. A pot with the mouth downward, resembling a medical cupping vessel for bloodletting, represents the womb. From the bottom of this cupping vessel two curved lines on each side illustrate the ligaments and uterine tubes, first discovered by Herophilos of Alexandria (ca. 330–260 BC). A key attached to the pot alludes to the closing and opening of the womb. The figure of Ouroborus, a snake eating its tail, encloses the scene. Greek magical spells are often inscribed on the other side of these amulets. Many of these amulets came from the personal collection of Campbell Bonner (1876–1954), and are now held at the University of Michigan Special Collections Library (SCL).