This is the only illustration to Realdus Colombus's De re anatomica, published in Venice in 1559, the year of his death. It is known, however, that he had planned an illustrated text. In his letter to Duke Cosimo de'Medici of 17 April 1548 he requests leave from his post as lecturer in anatomy at the University in Pisa in order to work on his busok, mentioning the assistance he is receiving from the "leading painter in the world" as well as how, on a previous stay in Rome, he dissected cadavers and supervised artists. This "leading painter" has usually been identified as Michelangelo, whose friendship with Colombus is documented in the 1553 biography of the artist by Ascanio Condivi. Colombus dispatched the body of "a young and very handsome moor" for Michelangelo to dissect and also treated him successfully for kidney stones. Colombus is noted for offering an early description of pulmonary circulation and for being a proponent of vivisection, the subject of the fourteenth book of De re anatomica. In the title page, the dissection is being followed by several observers, two of whom are consulting books, one of which is illustrated. At the lower left a young man is seated, taking notes or sketching on a pad.