In 1805, Franz Joseph Gall (1758-1828) first publicly presented his theory that a person’s character and mental abilities could be detected from the shape of their skull. He claimed the brain was composed of ‘cerebral organs’, each controlling a personality trait. In his theory, the strength of each organ corresponded to its size in the brain, and the skull fitted tightly around these organs so the resulting bumps could be perceived on the outside.

Phrenology became a popular reform movement. An analysis was thought to show a person’s weaknesses, which could be corrected by targeted education. Model heads with the ‘cerebral organs’ mapped were mass manufactured for use by the huge number of professional and amateur phrenologists. This one was sold by Frederick Bridges, a famous English phrenologist, and owned by a medical student at Aberdeen.

Many people were sceptical of phrenology. These essays criticise the theory, concluding that it is false – for example, the shape of the brain does not create a corresponding shape on the outer surface of the skull. The accompanying illustration caricatures a phrenology examination: the bulbous, red, newly shaven head of a patient is measured by a gangly phrenologist.

When plaster copies of Napoleon’s death mask were circulated, phrenologists were disappointed by its distinctly average features. They soon came up with explanations. “The size of the brain had in probability already decreased by the combined effects of inactivity and disease” after the emperor’s long imprisonment, according to the Phrenological Journal; or the bumps signifying his great talents would have been on the back of the head, which was not cast.

While Napoleon was ridiculed in British caricatures, in officially sanctioned depictions in France the emperor was depicted heroically, with a large cranium and ‘strong’ features.