In the late 1480s Leonardo conceived the idea of writing a treatise on anatomy. Initially he was hampered by a lack of material to dissect, but he was able to obtain one or more human skulls, and made a number of exquisitely detailed and accurate drawings of the sectioned skull on the pages of a small notebook. Here he studies the position of the facial cavities in relation to the surface features, and in the left margin, in his typical mirror-writing, he discusses the form and number of teeth in the human jaw.

No. 2a

In this drawing Leonardo attempted to locate the senso comune, the point in the brain where all the sensory nerves converged. This was the interface between the world and the mind, and thus Leonardo perceived it as the centre of one’s being. He located the senso comune at the mid-point of the cranium from top to bottom and a third of the way from front to back.

No. 2b