Prior to his extensive investigation of the human body through anatomical dissection, Leonardo created inner bodily mechanisms that perfectly fulfilled their functions, such as the neurological system illustrated in this schematized diagram of the network of nerves between the neck and the arm.

In the upper drawing, cervical vertebrae are “sawn through” to reveal a central and two lateral nerve cords. In the lower drawing the bones are removed, leaving the nerves and the base of the brain exposed.