Finally, Leonardo made a small wax model of the proposed statue and showed it to Ludovico. The nobleman was impressed by its originality. Most of the ideas contributed by other sculptors were mere variations of what had already been done many times. Also, the other plans called for bronze of not more than two thousand pounds, while Leonardo envisioned a statue fifty times that size! Ludovico awarded the commission to Leonardo. Leonardo was to work on this commission for ten years and it was destined never to be immortalized in bronze, for reasons that will be explained later. His energies, as usual, were poured into many schemes. Growing out of his work on the monument he planned one book on the subject of casting in bronze and another on the anatomy of the horse. But the one subject, which he began to study in this period and which would occupy the remainder of his life, was the study of human anatomy. So Leonardo, in the midst of all his other activities, wrote in his notes, “On the second day of April 1489 the book entitled _Of the Human Figure_.” The sources of anatomical study up to Leonardo’s day had been the Greeks—Hippocrates and Galen—and the Arab—Avicenna. Books on this subject were few, and the anatomical diagrams were crude and inaccurate. Galen, for example, had based his studies on the dissection of monkeys. Renaissance anatomists had explained his errors by pointing out that man had probably changed since Galen’s time. The Church had stepped in during the fourteenth century with an edict that was interpreted as a prohibition against dissection of the human body. In Italy, however, there were some dissections. They could only use, for this purpose, the bodies of criminals, slaves, and people of foreign birth. In Florence, anatomy was studied by the artists, and Leonardo had undoubtedly watched Pollaiuolo at work on a corpse that that artist had dissected. In 1489 Leonardo, from the results of his own investigation, produced drawings of the skull and backbone whose careful attention to detail are—even today—classics in art and anatomy. With infinite patience and with a saw of his own invention he had halved a skull and drew for the first time with accuracy the curves of the frontal and sphenoid bones. He drew the lachrymal (tear) canal, and he was the first to show the cavity in the superior maxillary bone—not discovered again until 1651, by Highmore—now named “the antrum of Highmore.” He was the first to demonstrate the double curvature of the spine and its accompanying vertebrae, the inclination of the sacrum, the shape of the rib cage, and the true position of the pelvis. He planned a whole series of books that would include from head to foot and from inside to outside every section of the human apparatus.