Four heads of men who each exhibit one of the four temperaments: (clockwise from top left) lymphatic, sanguine, bilious, and nervous. Engraving by W. Johnson and A.K. Johnson, early 19th century.

Licence: Public Domain Mark

Credit: Four heads of men who each exhibit one of the four temperaments: (clockwise from top left) lymphatic, sanguine, bilious, and nervous. Engraving by W. Johnson and A.K. Johnson, early 19th century. Wellcome Collection. Source: Wellcome Collection.