“Favus.” Photograph © Private Collection, Archives Charmet / The Bridgeman Art Library. Reproduced with permission.

This color engraving is an illustration from a 19th century dermatology text by Daniel Cornelius Danielssen (1815 – 1894) that was published in 1892. The picture is of a patient with tinea favosa, usually caused by Trichophyton schoenleinii. Dr. Danielssen was a leader in leprosy research in Norway and published extensively on his observations about the disease. Although he thought that leprosy was inherited, on the basis of the pattern of cases among farm families that he documented in western Norway, his student Gerhard Henrick Armauer Hansen (1841–1912) disputed this conclusion and identified Mycobacterium leprae as the cause of leprosy in 1873. (Ann Arvin, Cover Art Editor)