The Battle of Anghiari (Leonardo da Vinci)
In 1504 Leonardo da Vinci was given the commission by gonfaloniere Piero Soderini, a contract signed by Niccolò Machiavelli, to decorate the Hall of Five Hundred. At the same time his rival Michelangelo, who had just finished his "David", was designated the opposite wall. This was the only time that Leonardo da Vinci and Michelangelo worked together on the same project. The painting of Michelangelo depicted an episode from the Battle of Cascina, when a group of bathing soldiers was surprised by the enemy. However Michelangelo did not stay in Florence long enough to complete the project. He was able to finish his cartoon, but only began the painting. He was invited back to Rome in 1505 by the newly appointed Pope Julius II and was commissioned to build the Pope's tomb.
Separation of Light from Darkness
Of note is that in an article published in the "Journal of the American Medical Association" in October 1990, Frank Meshberger, an obstetrician-gynecologist from Indiana, explained that Michelangelo similarly concealed an image of the brain in the shroud surrounding God in the "Creation of Adam". Since Michelangelo painted the "Creation of Adam" and the "Separation of Light from Darkness", along with two other Genesis panels, as a single thematic unit between the winter of 1511 and October 1512, it is possible that these four central panels have an underlying anatomical motif. Indeed, Garabed Eknoyan, a nephrologist from Baylor College of Medicine, proposed in an article published in "Kidney International" in March 2000 that Michelangelo concealed an image of a kidney in the "Separation of Land and Water", the third panel in the Genesis series. Michelangelo was particularly interested in kidney function because he suffered from kidney stones throughout his adult life and documented this interest in his letters and poems, according to Eknoyan.