'The eye, whose use and operation are so clearly shown to us by experience, has been defined in one way by an infinite number of authors, up to my time, and I find it is completely different.' Leonardo proceeded to make his investigations with drawings and models, and enthroned site as king of the senses. He wrote, 'The images of the objects placed before the eye passed to the vitreous sphere by the gate of the pupil, and may intersect within this pupil.' He thought the image had now been inverted, and drew a schematic eye, which shows a second inversion in the misplaced spherical lens, so that the image was the right way up. When he reached the 'common sense'. The modern diagram shows the lens correctly placed. Images striking the retina are inverted, and are adjusted in the brain.