In 1489 Leonardo was able to obtain a human skull. He sectioned it to investigate its structure, and recorded his findings in meticulous drawings on the pages of a small notebook. Leonardo attempted to infer the paths of the nerves and the form of the brain, hoping to understand phenomena such as the senses and the emotions. But these studies proved to be fruitless, and in the early 1490s Leonardo’s first period of anatomical work came to a halt.