Recto: The layers of the scalp, and the cerebral ventricles. Verso: Studies of the head

The principal drawing imagines the head sectioned through the middle, its layers likened to those of an onion, and listed as ‘hair; scalp; muscular flesh; pericranium arising from the dura mater; cranium, that is, bone; dura mater; pia mater; brain’. Leonardo correctly shows the meningeal membrane of the dura mater extending along the optic nerve to the eye. Within the brain, Leonardo drew the cerebral ventricles as three bulbous cavities. These were believed to house the mental faculties: the first was where the mind’s ‘raw material’ was gathered – the senso commune, imagination and fantasy; in the second this information was processed, through reasoning and so on; and the third was where the results were stored, in the memory. At lower right the head is seen from above with the crown of the head flipped back, the optic and auditory nerves converging on the first ventricle. But Leonardo was unconvinced by this arrangement, repeatedly trying different layouts, and he later abandoned the traditional system of the localisation of mental faculties. On the verso of this sheet is a drawing of an old man's head, full face. To the right are various anatomical scribbles of a head and cranium, together with a rough sketch of a head in profile, facing left, not by Leonardo. Text adapted from Leonardo da Vinci: A life in drawing, London, 2018