illustrations of a zonary (band-shaped) placenta and fetal membrane in the 1543 edition of De Fabrica; Vesalius does so relying on Galenic medicine which used canine reproductive organs rather than human female reproductive organs. The illustrations are corrected in the 1555 edition. The new images depict a discoid placenta and fetal membrane. Book 6: The Heart and Associated Organs, Book 7: The Brain These books describe the structure and functions of the heart and the organs of respiration, the brain and its coverings, the eye, the organs of sensation, and the nerves of the limbs. A chapter is also devoted to the dissection of the eye. Vesalius describes the organs of the body in great detail by commenting "on the variable strength of the attachment of the pleura to the thoracic walls, the strong attachment of the pericardium to the diaphragm, the shape and orientation of the ventricles of the heart, and the description of the semilunar valves." He closes each book with a chapter on the correct way to dissect the heart and the brain respectively. Galen's errors Galen, the prominent Greek physician, surgeon and philosopher in the Roman empire had written on anatomy among other topics, but his work remained largely unchecked until the time of Vesalius. The Fabrica rectified some of Galen's worst errors, including the notion that the great blood vessels originated from the liver. Other errors rectified included the idea that the human mandible was in two parts (it is, in fact, in one part) and that men had fewer ribs than women. Disproving this decreased Vesalius' popularity with the Church as it contradicted the Biblical understanding of Adam and Eve. While examining a human corpse, Vesalius discovered that Galen's observations were inconsistent with those of his, due to Galen's use of animal (dog and monkey) cadavers. Overall, Vesalius's use of human corpses allowed him to rectify approximately 300 of Galen's errors. Even with his improvements, however, Vesalius clung to some of Galen's errors, such as the idea that a different type of blood flowed through veins than through arteries. It was not until William Harvey's work on the circulation of the blood (De Motu Cordis, 1628) that this misconception of Galen's would be rectified in Europe. Publication 1543 edition Vesalius had the work published at the age of 28, taking great pains to ensure its quality, and dedicated it to Charles V, Holy Roman