This is one of a series of studies of the human skull by Leonardo. Based on direct observation, the drawings are famous for their anatomical accuracy and the breathtaking virtuosity of the pen and ink technique employed.

In this meticulously observed side view of the sagittal section, Leonardo plots the site of the sensus communis, which he believed was the locus of the human soul, at the intersection of upright and diagonal lines seen within the tilted plane at a point that marks the proportional centre of the skull.